[EE] Xenon flash bulb system missing strobes

[Darron Black]

I've got a xenon flash system providing the light for a flying image
capture of components on a pick and place machine.  Here's the datasheet
(MVS-7020-04) http://www.visionlighttech.com/sap/datasheets/302-7020-10.pdf

Lately, it's taken to missing strobes.  The pick and place was not
designed to handle missed strobes, and when that happens it throws away
ALL the parts on the head at the time.

I figured it was the bulb at first, and a brand new bulb appeared to
help for a bit... but it's back to failing again.  I've replaced the
bulb a second time with very little improvement.

Since the xenon flash system is about ~16 years old... I figure some
capacitors may need replacing.


So far, I've really only got as far as the big capacitor attached to the
bulb itself.  It's 12uF +/- 10% nominal, and two different meter
readings put it at 13.4 and 13.6 uF.  It's of this type:
https://chicagocondenser.com/cmp/

It uses "polyester resin film and the finest grade Kraft paper
impregnated with mineral oil" (or silicone dielectric fluid, it's not
clear which)

Can this capacitor actually GAIN capacitance as it ages?


I don't really see a safe way to measure this system while active to see
what's going on.  It's pretty high voltage, and then there's the
blinding levels of light output.  It's got a door interlock to make sure
you don't do something stupid like try to run it open... so I haven't.


Any other suggestions?   Does anyone else know of another common failure
mode for flash systems?  The system is difficult to disassemble (or
reassemble, rather), so I'm starting with this cap.


Darron

***@griffin.net

[Sean Breheny]

Hi Darron,

If I recall correctly, these systems work by having a medium voltage supply
connected across the bulb and then EITHER a separate trigger electrode OR a
some kind of coupling (like a transformer) in series with the medium
voltage supply to be able to introduce a firing pulse. My guess would be
that this trigger pulse is not happening or is not being coupled properly.
Does the bulb have two or three terminals?

Sean

Post by Darron Black
I've got a xenon flash system providing the light for a flying image
capture of components on a pick and place machine. Here's the datasheet
(MVS-7020-04) http://www.visionlighttech.com/sap/datasheets/302-7020-
10.pdf
Lately, it's taken to missing strobes. The pick and place was not
designed to handle missed strobes, and when that happens it throws away
ALL the parts on the head at the time.
I figured it was the bulb at first, and a brand new bulb appeared to
help for a bit... but it's back to failing again. I've replaced the
bulb a second time with very little improvement.
Since the xenon flash system is about ~16 years old... I figure some
capacitors may need replacing.
So far, I've really only got as far as the big capacitor attached to the
bulb itself. It's 12uF +/- 10% nominal, and two different meter
https://chicagocondenser.com/cmp/
It uses "polyester resin film and the finest grade Kraft paper
impregnated with mineral oil" (or silicone dielectric fluid, it's not
clear which)
Can this capacitor actually GAIN capacitance as it ages?
I don't really see a safe way to measure this system while active to see
what's going on. It's pretty high voltage, and then there's the
blinding levels of light output. It's got a door interlock to make sure
you don't do something stupid like try to run it open... so I haven't.
Any other suggestions? Does anyone else know of another common failure
mode for flash systems? The system is difficult to disassemble (or
reassemble, rather), so I'm starting with this cap.
Darron
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[Van Horn, David]

Sounds to me like the trigger transformer or associated parts are failing.
The tube will wear out eventually but it should be slow and failing bulk caps should give you flashes at lower light output before they completely fail, plus they wouldn't come back from the dead.
Recharge time might be an issue if the caps can't get charged between shots, but that should give you pretty consistent misses at given positions but good shots at other positions, based on the time available to recharge.
Recharge time could be pretty minimal on a line powered system though, as opposed to seconds on a common camera strobe.


-----Original Message-----
From: piclist-***@mit.edu [mailto:piclist-***@mit.edu] On Behalf Of Sean Breheny
Sent: Wednesday, January 24, 2018 12:16 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Xenon flash bulb system missing strobes

Hi Darron,

If I recall correctly, these systems work by having a medium voltage supply connected across the bulb and then EITHER a separate trigger electrode OR a some kind of coupling (like a transformer) in series with the medium voltage supply to be able to introduce a firing pulse. My guess would be that this trigger pulse is not happening or is not being coupled properly.
Does the bulb have two or three terminals?

Sean

Post by Darron Black
I've got a xenon flash system providing the light for a flying image
capture of components on a pick and place machine. Here's the
datasheet
(MVS-7020-04) http://www.visionlighttech.com/sap/datasheets/302-7020-
10.pdf
Lately, it's taken to missing strobes. The pick and place was not
designed to handle missed strobes, and when that happens it throws
away ALL the parts on the head at the time.
I figured it was the bulb at first, and a brand new bulb appeared to
help for a bit... but it's back to failing again. I've replaced the
bulb a second time with very little improvement.
Since the xenon flash system is about ~16 years old... I figure some
capacitors may need replacing.
So far, I've really only got as far as the big capacitor attached to
the bulb itself. It's 12uF +/- 10% nominal, and two different meter
https://chicagocondenser.com/cmp/
It uses "polyester resin film and the finest grade Kraft paper
impregnated with mineral oil" (or silicone dielectric fluid, it's not
clear which)
Can this capacitor actually GAIN capacitance as it ages?
I don't really see a safe way to measure this system while active to
see what's going on. It's pretty high voltage, and then there's the
blinding levels of light output. It's got a door interlock to make
sure you don't do something stupid like try to run it open... so I haven't.
Any other suggestions? Does anyone else know of another common failure
mode for flash systems? The system is difficult to disassemble (or
reassemble, rather), so I'm starting with this cap.
Darron
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[Darron Black]

It is quite odd how it's failing.  It's not consistent, apart from
starting off good early in the day and getting progressively worse until
it's skipping one out of every 3-5 flashes or so. (Temperature?)   When
it is failing, it is quite random and not something like "every 3rd of a
sequence of flashes".  It will fail even on the very first flash of a
sequence after a 3 second wait, for example... and then get the
subsequent flashes just fine. It's weird.

The box says it's designed for 20Hz flashes... the actual rate when the
head passes is more like 4Hz.  The head will have anywhere from 1-7
parts to image, and then there's probably 2-5 seconds between head passes.

In fact, the workaround when it gets really bad (and I get tired of
losing money in trashed parts) is to turn off all but one nozzle at a
time... which dramatically slows things down but at least the "3 tries
until parts are trashed" logic lets it keep going.  The actual "parts
are trashed" event occurs if a single flash out of a head pass is missed
3 times in a row (if there's a miss, the head will back up and retry the
pass twice then trash the parts and pause the job).  With 5-7
parts/flashes per pass, it starts to get pretty likely to occur.


Darron

Post by Van Horn, David
Sounds to me like the trigger transformer or associated parts are failing.
The tube will wear out eventually but it should be slow and failing bulk caps should give you flashes at lower light output before they completely fail, plus they wouldn't come back from the dead.
Recharge time might be an issue if the caps can't get charged between shots, but that should give you pretty consistent misses at given positions but good shots at other positions, based on the time available to recharge.
Recharge time could be pretty minimal on a line powered system though, as opposed to seconds on a common camera strobe.
-----Original Message-----
Sent: Wednesday, January 24, 2018 12:16 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Xenon flash bulb system missing strobes
Hi Darron,
If I recall correctly, these systems work by having a medium voltage supply connected across the bulb and then EITHER a separate trigger electrode OR a some kind of coupling (like a transformer) in series with the medium voltage supply to be able to introduce a firing pulse. My guess would be that this trigger pulse is not happening or is not being coupled properly.
Does the bulb have two or three terminals?
Sean

Post by Darron Black
I've got a xenon flash system providing the light for a flying image
capture of components on a pick and place machine. Here's the datasheet
(MVS-7020-04) http://www.visionlighttech.com/sap/datasheets/302-7020-
10.pdf
Lately, it's taken to missing strobes. The pick and place was not
designed to handle missed strobes, and when that happens it throws
away ALL the parts on the head at the time.
I figured it was the bulb at first, and a brand new bulb appeared to
help for a bit... but it's back to failing again. I've replaced the
bulb a second time with very little improvement.
Since the xenon flash system is about ~16 years old... I figure some
capacitors may need replacing.
So far, I've really only got as far as the big capacitor attached to
the bulb itself. It's 12uF +/- 10% nominal, and two different meter
https://chicagocondenser.com/cmp/
It uses "polyester resin film and the finest grade Kraft paper
impregnated with mineral oil" (or silicone dielectric fluid, it's not
clear which)
Can this capacitor actually GAIN capacitance as it ages?
I don't really see a safe way to measure this system while active to
see what's going on. It's pretty high voltage, and then there's the
blinding levels of light output. It's got a door interlock to make
sure you don't do something stupid like try to run it open... so I haven't.
Any other suggestions? Does anyone else know of another common failure
mode for flash systems? The system is difficult to disassemble (or
reassemble, rather), so I'm starting with this cap.
Darron
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[Sean Breheny]

I think the Perkin Elmer part is either a transformer or an isolated
high-voltage generator. It's just a guess but I would suspect that part may
be failing. It could be that the potting has developed a leak which is
allowing air into some place where it isn't supposed to be, making it
possible for it to sometimes arc-over internally instead of producing a
proper output pulse. If this is just on the edge of arcing, then it could
indeed display the random behavior you mention because there are so many
variables involved in whether an arc happens (air pressure, temperature,
humidity, presence of ionizing radiation/variation in the natural
background radiation)

I think your idea of looking for the proper input trigger pulse to the
entire unit is a good idea. If that turns out to be OK, then the next steps
depend on your confidence and ability. Maybe take a photo of the innards of
the whole unit and let us have a look to judge the probability of whether
something else other than the Perkin Elmer unit could be at fault.

It is quite odd how it's failing. It's not consistent, apart from
starting off good early in the day and getting progressively worse until
it's skipping one out of every 3-5 flashes or so. (Temperature?) When
it is failing, it is quite random and not something like "every 3rd of a
sequence of flashes". It will fail even on the very first flash of a
sequence after a 3 second wait, for example... and then get the
subsequent flashes just fine. It's weird.
The box says it's designed for 20Hz flashes... the actual rate when the
head passes is more like 4Hz. The head will have anywhere from 1-7
parts to image, and then there's probably 2-5 seconds between head passes.
In fact, the workaround when it gets really bad (and I get tired of
losing money in trashed parts) is to turn off all but one nozzle at a
time... which dramatically slows things down but at least the "3 tries
until parts are trashed" logic lets it keep going. The actual "parts
are trashed" event occurs if a single flash out of a head pass is missed
3 times in a row (if there's a miss, the head will back up and retry the
pass twice then trash the parts and pause the job). With 5-7
parts/flashes per pass, it starts to get pretty likely to occur.
Darron

Post by Van Horn, David
Sounds to me like the trigger transformer or associated parts are

failing.

Post by Van Horn, David
The tube will wear out eventually but it should be slow and failing bulk

caps should give you flashes at lower light output before they completely
fail, plus they wouldn't come back from the dead.

Post by Van Horn, David
Recharge time might be an issue if the caps can't get charged between

shots, but that should give you pretty consistent misses at given positions
but good shots at other positions, based on the time available to recharge.

Post by Van Horn, David
Recharge time could be pretty minimal on a line powered system though,

as opposed to seconds on a common camera strobe.

Post by Van Horn, David
-----Original Message-----

Behalf Of Sean Breheny

Post by Van Horn, David
Sent: Wednesday, January 24, 2018 12:16 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Xenon flash bulb system missing strobes
Hi Darron,
If I recall correctly, these systems work by having a medium voltage

supply connected across the bulb and then EITHER a separate trigger
electrode OR a some kind of coupling (like a transformer) in series with
the medium voltage supply to be able to introduce a firing pulse. My guess
would be that this trigger pulse is not happening or is not being coupled
properly.

Post by Van Horn, David
Does the bulb have two or three terminals?
Sean

Post by Darron Black
I've got a xenon flash system providing the light for a flying image
capture of components on a pick and place machine. Here's the datasheet
(MVS-7020-04) http://www.visionlighttech.com/sap/datasheets/302-7020-
10.pdf
Lately, it's taken to missing strobes. The pick and place was not
designed to handle missed strobes, and when that happens it throws
away ALL the parts on the head at the time.
I figured it was the bulb at first, and a brand new bulb appeared to
help for a bit... but it's back to failing again. I've replaced the
bulb a second time with very little improvement.
Since the xenon flash system is about ~16 years old... I figure some
capacitors may need replacing.
So far, I've really only got as far as the big capacitor attached to
the bulb itself. It's 12uF +/- 10% nominal, and two different meter
https://chicagocondenser.com/cmp/
It uses "polyester resin film and the finest grade Kraft paper
impregnated with mineral oil" (or silicone dielectric fluid, it's not
clear which)
Can this capacitor actually GAIN capacitance as it ages?
I don't really see a safe way to measure this system while active to
see what's going on. It's pretty high voltage, and then there's the
blinding levels of light output. It's got a door interlock to make
sure you don't do something stupid like try to run it open... so I

haven't.

Post by Van Horn, David

Post by Darron Black
Any other suggestions? Does anyone else know of another common failure
mode for flash systems? The system is difficult to disassemble (or
reassemble, rather), so I'm starting with this cap.
Darron
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[Darron Black]

Sean,

Two terminals.  One's on the center on the back of the bulb, the other
is connected to the metal frame itself.

The bulb has it's center terminal connected to a potted rectangular box,
Perkin Elmer XP-0858, which looks exactly like this:
https://www.ebay.com/itm/PERKIN-ELMER-XP-0858-/251794123055 .  That
potted box has four leads, two thicker leads and two thinner leads. 
Could be a weird potted transformer... I'm not sure what it is.

The other thick lead coming out of that potted box goes to the positive
terminal of the big 12uF 750V capacitor.  The big capacitor's negative
lead goes to the metal frame terminal of the bulb.  Both terminals of
the capacitor, along with the thin wires from the potted box, go to the
main PCB.

The main PCB has several other capacitors on it, one with a big electric
shock warning sticker on it.  They're not really that big, maybe 30mm
long cylinders, 15mm diameter.

I'm still avoiding taking the main PCB out, as I'm not sure I'll be able
to get it back in.  My next test is to button it all back up and monitor
the trigger pulse going into this unit to see if I see anything
abnormal.  (Maybe it's not this box at all)   I think I recall noticing
the trigger pulse from the pick and place was not quite in spec before,
back when I first replaced the bulb.  I dropped the investigation when
the replaced bulb seemed to solve the problem for a while.

Darron

Post by Sean Breheny
Hi Darron,
If I recall correctly, these systems work by having a medium voltage supply
connected across the bulb and then EITHER a separate trigger electrode OR a
some kind of coupling (like a transformer) in series with the medium
voltage supply to be able to introduce a firing pulse. My guess would be
that this trigger pulse is not happening or is not being coupled properly.
Does the bulb have two or three terminals?
Sean

Post by Darron Black
I've got a xenon flash system providing the light for a flying image
capture of components on a pick and place machine. Here's the datasheet
(MVS-7020-04) http://www.visionlighttech.com/sap/datasheets/302-7020-
10.pdf
Lately, it's taken to missing strobes. The pick and place was not
designed to handle missed strobes, and when that happens it throws away
ALL the parts on the head at the time.
I figured it was the bulb at first, and a brand new bulb appeared to
help for a bit... but it's back to failing again. I've replaced the
bulb a second time with very little improvement.
Since the xenon flash system is about ~16 years old... I figure some
capacitors may need replacing.
So far, I've really only got as far as the big capacitor attached to the
bulb itself. It's 12uF +/- 10% nominal, and two different meter
https://chicagocondenser.com/cmp/
It uses "polyester resin film and the finest grade Kraft paper
impregnated with mineral oil" (or silicone dielectric fluid, it's not
clear which)
Can this capacitor actually GAIN capacitance as it ages?
I don't really see a safe way to measure this system while active to see
what's going on. It's pretty high voltage, and then there's the
blinding levels of light output. It's got a door interlock to make sure
you don't do something stupid like try to run it open... so I haven't.
Any other suggestions? Does anyone else know of another common failure
mode for flash systems? The system is difficult to disassemble (or
reassemble, rather), so I'm starting with this cap.
Darron
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[a***@stfc.ac.uk]

Sean,
Two terminals.  One's on the center on the back of the bulb, the other is connected to the metal frame itself.
https://www.ebay.com/itm/PERKIN-ELMER-XP-0858-/251794123055 .  That potted box has four leads,
two thicker leads and two thinner leads. Could be a weird potted transformer... I'm not sure what it is.

This sounds like it is a transformer with voltage multiplier on the secondary, rather like a TV EHT output stage, but looking at the data sheet you referenced in your first post it lists 750V maximum, so I suspect it may be only a single or two stage rectifier. They tend to pot these beasts to keep moisture out of the high voltage area as much as possible and eliminate corona.

The other thick lead coming out of that potted box goes to the positive terminal of the big 12uF 750V capacitor. 
The big capacitor's negative lead goes to the metal frame terminal of the bulb.  Both terminals of the capacitor,
along with the thin wires from the potted box, go to the main PCB.

If you operate it and check with a scope I suspect the thin wires are driven with a square wave of varying amplitude. The amplitude will set he output voltage.

The main PCB has several other capacitors on it, one with a big electric shock warning sticker on it.
  They're not really that big, maybe 30mm long cylinders, 15mm diameter.
I'm still avoiding taking the main PCB out, as I'm not sure I'll be able to get it back in. 
My next test is to button it all back up and monitor the trigger pulse going into this
unit to see if I see anything abnormal.  (Maybe it's not this box at all)  
I think I recall noticing the trigger pulse from the pick and place was not quite in spec
before, back when I first replaced the bulb.  I dropped the investigation when the
replaced bulb seemed to solve the problem for a while.

OK, that sounds a sensible thing to do, a 5V signal into an opto (as mentioned in data sheet) is a lot easier to measure ...
It will be worth going down that route first.

There is clearly a heat fault of some form from your earlier description - have you checked the fans are all running at speed (how long since the bearings were lubricated - I find it makes a difference to muffin fans) and the dust filters cleaned or replaced?

My experience is mostly with flash guns for photographic use, which used three electrode tubes, but later on I did get involved in servicing microfiche duplicators that used a two electrode tube, but I cannot remember how the tube was triggered.

[Sean Breheny]

I interpreted that 750V figure in the datasheet as the maximum voltage for
the main discharge, not the trigger pulse. I think the trigger pulse is in
the range of about 10 to 20kV, maybe even more.

Post by a***@stfc.ac.uk
This sounds like it is a transformer with voltage multiplier on the
secondary, rather like a TV EHT output stage, but looking at the data sheet
you referenced in your first post it lists 750V maximum, so I suspect it
may be only a single or two stage rectifier. They tend to pot these beasts
to keep moisture out of the high voltage area as much as possible and
eliminate corona.

[a***@stfc.ac.uk]

I interpreted that 750V figure in the datasheet as the maximum voltage for the main discharge,
not the trigger pulse. I think the trigger pulse is in the range of about 10 to 20kV, maybe even more.

Oh, I agree. The electronic flash guns for photographic use had somewhere between 350 and 500V on the main capacitor. Commercial ones were always 500V, with the best ones having 4 500uF capacitors that could be switched out to give half and quarter power by using two or one capacitor. The inverter would recharge 2000uF in under 10 seconds after a flash. Would take a bit longer, probably around 15 seconds from a cold start with 0V on the caps. These used a separate trigger transformer to drive the trigger electrode which was a metallic paint stripe on the outside of the tube for some models, others had what looked like a metal clamp on the outside of the tube at the ground end as I recall it. The energy in getting a handful of atoms ionised at that point was enough to make the whole tube ionise.

This sounds like it is a transformer with voltage multiplier on the
secondary, rather like a TV EHT output stage, but looking at the data
sheet you referenced in your first post it lists 750V maximum, so I
suspect it may be only a single or two stage rectifier. They tend to
pot these beasts to keep moisture out of the high voltage area as much
as possible and eliminate corona.

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[Darron Black]

Ok, I've somewhat characterized the trigger input, at least in it's
"normal" state.  It was cold, so there were no misses during testing for
now.  I'm leaving my test setup in place to try again tomorrow to see if
the system starts to fail after warming up a while.

The pick and place system pulses the "Trigger+" input to ~5V when it
wants a strobe... but the pulse lasts for 5 ms.  The documentation I can
find says the trigger should be "10-100 microseconds".  The "Trigger-"
input stays at 0V.  I recall now that this is what I saw before when
initially looking at this problem.  It's 50x too long.

I also remember seeing that the pick and place was using a VREF
intensity signal, which should be 5-10V according to docs, incorrectly. 
The intensity could be controlled by each individual part's database
entry, and a low value in the software would output around 2-3V from
what I recall.  The spec says there's a 75:1 ratio on the bulb voltage
relative to VREF, so that would be too low on the bulb. I recall reading
that this could reduce bulb life, so I made a modification to the setup
a few months ago to disable the analog VREF signal input entirely (by
disconnecting it in the DB9 connector shell) and switching the strobe
unit's internal selector switch from EXT to INT for intensity source.
This was somewhere around 9 months to 1.5 years ago.

So... can anyone think of a reason that a trigger strobe that lasts too
long could cause problems?   Would this potentially pass directly
through as the "high voltage start" trigger, and subject the bulb to a
way-too-long initial voltage?

The relatively new bulb currently in the unit looks pretty clean.  I
remember the original bulb looking slightly burned in a spot or two, but
this one looks fine.

I can reasonably easily repurpose a VFD display interface board of ours
(with an onboard FPGA and 5V level translators) to reconfigure the
strobe to whatever duration I want... probably 50 microseconds?  The
delay that way would be very minimal and low jitter.

What is your interpretation of the trigger input spec as "+5 volt TTL
pulse into 4N36 opto-isolator with 150 ohm nominal series resistor" ?  I
interpret that to describe the isolation hardware in the strobe unit,
which implies a 33mA current draw maximum.  My FPGA board does +/- 50mA
per pin, so that'd be fine.  I could play it safe and put another 150
ohms in series with that... ?


Darron

Post by a***@stfc.ac.uk

I interpreted that 750V figure in the datasheet as the maximum voltage for the main discharge,
not the trigger pulse. I think the trigger pulse is in the range of about 10 to 20kV, maybe even more.

Oh, I agree. The electronic flash guns for photographic use had somewhere between 350 and 500V on the main capacitor. Commercial ones were always 500V, with the best ones having 4 500uF capacitors that could be switched out to give half and quarter power by using two or one capacitor. The inverter would recharge 2000uF in under 10 seconds after a flash. Would take a bit longer, probably around 15 seconds from a cold start with 0V on the caps. These used a separate trigger transformer to drive the trigger electrode which was a metallic paint stripe on the outside of the tube for some models, others had what looked like a metal clamp on the outside of the tube at the ground end as I recall it. The energy in getting a handful of atoms ionised at that point was enough to make the whole tube ionise.

This sounds like it is a transformer with voltage multiplier on the
secondary, rather like a TV EHT output stage, but looking at the data
sheet you referenced in your first post it lists 750V maximum, so I
suspect it may be only a single or two stage rectifier. They tend to
pot these beasts to keep moisture out of the high voltage area as much
as possible and eliminate corona.

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[p***@roadrunner.com]

I can reasonably easily repurpose a VFD display interface board of ours (with an onboard FPGA and 5V level translators) to reconfigure the strobe to whatever duration I want... probably 50 microseconds? The delay that way would be very minimal and low jitter.

How about a simple 555 circuit? An FPGA seems a bit of overkill to generate one pulse :-)

- - Bob Ammerman
RAm Systems

[Darron Black]

It's actually easier.  The FPGA board is already built (I just ran 100
of them a couple days ago), I have an existing project for that specific
board that I can copy gut and rework, and I don't stock any 555s or
really nearly any through hole passives (heresy? :) )  I have so many
embedded Linux systems and FPGA boards lying around I tend to just grab
one of those for anything.

Your reaction is exactly like a retired EE friend of mine when I
suggested nearly the same FPGA board as a solution to his own pet
problem.  I told him I'd program an FPGA board of mine and give it to
him in an hour... he found the "overkill" unacceptable and proceeded to
tinker with a "simpler" circuit for probably a few weeks (really that
was more of a "getting around to it"  and waiting on parts problem).  I
suppose it was better for him as his solution is entirely fixable by
him, whereas my solution would need outside help again if something went
wrong. He had exactly what he wanted when he was done.


Darron

Post by p***@roadrunner.com

I can reasonably easily repurpose a VFD display interface board of ours (with an onboard FPGA and 5V level translators) to reconfigure the strobe to whatever duration I want... probably 50 microseconds? The delay that way would be very minimal and low jitter.

How about a simple 555 circuit? An FPGA seems a bit of overkill to generate one pulse :-)
- - Bob Ammerman
RAm Systems

[Darron Black]

Hmm, I reread my post and I decided the tone doesn't come across right. 
I had something come up and just bashed 'send' as I walked out (nearly
always a mistake).

My "your reaction" paragraph is 100% amused reflection about my friend
and 0% critical or "my way is better".  Although my way works for me, I
think very few other people have my particularly strange background that
makes it so (write FPGA code all the time, have virtually disposable
FPGA boards lying around everywhere, etc).

Bob's comment is surely the right way for most people to go.


Darron

Post by Darron Black
It's actually easier.  The FPGA board is already built (I just ran 100
of them a couple days ago), I have an existing project for that specific
board that I can copy gut and rework, and I don't stock any 555s or
really nearly any through hole passives (heresy? :) )  I have so many
embedded Linux systems and FPGA boards lying around I tend to just grab
one of those for anything.
Your reaction is exactly like a retired EE friend of mine when I
suggested nearly the same FPGA board as a solution to his own pet
problem.  I told him I'd program an FPGA board of mine and give it to
him in an hour... he found the "overkill" unacceptable and proceeded to
tinker with a "simpler" circuit for probably a few weeks (really that
was more of a "getting around to it"  and waiting on parts problem).  I
suppose it was better for him as his solution is entirely fixable by
him, whereas my solution would need outside help again if something went
wrong. He had exactly what he wanted when he was done.
Darron

Post by p***@roadrunner.com

I can reasonably easily repurpose a VFD display interface board of ours (with an onboard FPGA and 5V level translators) to reconfigure the strobe to whatever duration I want... probably 50 microseconds? The delay that way would be very minimal and low jitter.

How about a simple 555 circuit? An FPGA seems a bit of overkill to generate one pulse :-)
- - Bob Ammerman
RAm Systems

[Clint Jay]

If you can knock together a pulse generator that meets the spec of the
input in an hour then go for it but I suspect the fault will still be
present.

Think about it, it worked perfectly until recently, therefore something
changed, I would be amazed if the trigger input being longer than specified
is causing the problem plus a strobe is notoriously hard on the main
reservoir cap, the trigger transformer, the charging circuit for the
reservoir cap and as such it's highly likely that the problem is in the
horrible analogue circuitry, check resistor values, check capacitor values
and check solder joints.

It could also possibly be that the strobe tube is worn out, they have a
pretty well defined lifespan where it's specified to strike at a given
trigger voltage, outside that they become harder to strike and can misfire
or not strike at all.

By all rams tinker with triggering but my money would be elsewhere.

Post by Darron Black
Hmm, I reread my post and I decided the tone doesn't come across right.
I had something come up and just bashed 'send' as I walked out (nearly
always a mistake).
My "your reaction" paragraph is 100% amused reflection about my friend
and 0% critical or "my way is better". Although my way works for me, I
think very few other people have my particularly strange background that
makes it so (write FPGA code all the time, have virtually disposable
FPGA boards lying around everywhere, etc).
Bob's comment is surely the right way for most people to go.
Darron

It's actually easier. The FPGA board is already built (I just ran 100
of them a couple days ago), I have an existing project for that specific
board that I can copy gut and rework, and I don't stock any 555s or
really nearly any through hole passives (heresy? :) ) I have so many
embedded Linux systems and FPGA boards lying around I tend to just grab
one of those for anything.
Your reaction is exactly like a retired EE friend of mine when I
suggested nearly the same FPGA board as a solution to his own pet
problem. I told him I'd program an FPGA board of mine and give it to
him in an hour... he found the "overkill" unacceptable and proceeded to
tinker with a "simpler" circuit for probably a few weeks (really that
was more of a "getting around to it" and waiting on parts problem). I
suppose it was better for him as his solution is entirely fixable by
him, whereas my solution would need outside help again if something went
wrong. He had exactly what he wanted when he was done.
Darron

Post by p***@roadrunner.com

Post by Darron Black
I can reasonably easily repurpose a VFD display interface board of

ours (with an onboard FPGA and 5V level translators) to reconfigure the
strobe to whatever duration I want... probably 50 microseconds? The delay
that way would be very minimal and low jitter.

Post by p***@roadrunner.com
How about a simple 555 circuit? An FPGA seems a bit of overkill to

generate one pulse :-)

Post by p***@roadrunner.com
- - Bob Ammerman
RAm Systems

--
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View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

[Darron Black]

Clint,

Yeah, I have the trigger reconditioner ready to go but I do think like
you say this is unlikely to fix the problem.  I am just hoping the out
of spec trigger causes more heat than it should and fixing that might
give me back enough margin to be okay again.

I'll also check the outer temperature of the unit when it starts
failing, which I haven't done yet either.  Maybe just a big 12V fan
blowing over it would help.

I called the manufacturer and their app engineer of course recommended a
replacement unit.  She did say the out of spec trigger signal could
cause trouble with the trigger module, though.  I didn't get a sense of
how knowledgeable in this particular product she was, but it's a hopeful
sign that reconditioning could work.

I just found what may be a great deal on a replacement strobe unit off
ebay and bought that.  If anything, I could try the trigger module on
that unit if it doesn't work on it's own. Hopefully, I'll have a working
unit and an unreliable but usable spare this way.


I'll run the machine tomorrow with the reconditioner and see what
happens as the day progresses.


Today, I'm going to try to tap into the PC interface and see if I can
start figuring out the protocols.  I need a longer term solution for
when something that isn't replaceable dies on me. It's a good time to
finally build that CAN bus FPGA capture board, anyway.


Darron

Post by Clint Jay
If you can knock together a pulse generator that meets the spec of the
input in an hour then go for it but I suspect the fault will still be
present.
Think about it, it worked perfectly until recently, therefore something
changed, I would be amazed if the trigger input being longer than specified
is causing the problem plus a strobe is notoriously hard on the main
reservoir cap, the trigger transformer, the charging circuit for the
reservoir cap and as such it's highly likely that the problem is in the
horrible analogue circuitry, check resistor values, check capacitor values
and check solder joints.
It could also possibly be that the strobe tube is worn out, they have a
pretty well defined lifespan where it's specified to strike at a given
trigger voltage, outside that they become harder to strike and can misfire
or not strike at all.
By all rams tinker with triggering but my money would be elsewhere.

Post by Darron Black
Hmm, I reread my post and I decided the tone doesn't come across right.
I had something come up and just bashed 'send' as I walked out (nearly
always a mistake).
My "your reaction" paragraph is 100% amused reflection about my friend
and 0% critical or "my way is better". Although my way works for me, I
think very few other people have my particularly strange background that
makes it so (write FPGA code all the time, have virtually disposable
FPGA boards lying around everywhere, etc).
Bob's comment is surely the right way for most people to go.
Darron

It's actually easier. The FPGA board is already built (I just ran 100
of them a couple days ago), I have an existing project for that specific
board that I can copy gut and rework, and I don't stock any 555s or
really nearly any through hole passives (heresy? :) ) I have so many
embedded Linux systems and FPGA boards lying around I tend to just grab
one of those for anything.
Your reaction is exactly like a retired EE friend of mine when I
suggested nearly the same FPGA board as a solution to his own pet
problem. I told him I'd program an FPGA board of mine and give it to
him in an hour... he found the "overkill" unacceptable and proceeded to
tinker with a "simpler" circuit for probably a few weeks (really that
was more of a "getting around to it" and waiting on parts problem). I
suppose it was better for him as his solution is entirely fixable by
him, whereas my solution would need outside help again if something went
wrong. He had exactly what he wanted when he was done.
Darron

Post by p***@roadrunner.com

Post by Darron Black
I can reasonably easily repurpose a VFD display interface board of

ours (with an onboard FPGA and 5V level translators) to reconfigure the
strobe to whatever duration I want... probably 50 microseconds? The delay
that way would be very minimal and low jitter.

Post by p***@roadrunner.com
How about a simple 555 circuit? An FPGA seems a bit of overkill to

generate one pulse :-)

Post by p***@roadrunner.com
- - Bob Ammerman
RAm Systems

--
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View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

[Van Horn, David]

Good excuse to buy a Flir one pro!

[Darron Black]

David,

I have a seek thermal pro sensor that I use with an android tablet.  It
works great but it's a bit of a pain as the tablet always needs to be
charged when I want to use it.  It's really helped identify board failures.

I had a rash of unexplained failures off the assembly line that the
thermal sensor showed quite plainly were bad ceramic caps. Turns out an
alternate part was significantly thicker and the pick and place was
cracking some slamming them down on the board with the wrong height.  Oops.


Darron

***@griffin.net

832-867-7041 cell

Post by Van Horn, David
Good excuse to buy a Flir one pro!

[Van Horn, David]

I had a Seek also, but I recently changed to the FLIR as their software is better. Time lapse capability!

It's wonderful being able to see what's going on rather than guessing.


-----Original Message-----
From: Darron Black [mailto:***@griffin.net]
Sent: Thursday, January 25, 2018 10:14 AM
To: Microcontroller discussion list - Public.; Van Horn, David
Subject: Re: [EE] Xenon flash bulb system missing strobes

David,

I have a seek thermal pro sensor that I use with an android tablet.  It works great but it's a bit of a pain as the tablet always needs to be charged when I want to use it.  It's really helped identify board failures.

I had a rash of unexplained failures off the assembly line that the thermal sensor showed quite plainly were bad ceramic caps. Turns out an alternate part was significantly thicker and the pick and place was cracking some slamming them down on the board with the wrong height.  Oops.


Darron

***@griffin.net

832-867-7041 cell

Post by Van Horn, David
Good excuse to buy a Flir one pro!

[Darron Black]

Here's an update on the xenon strobe unit.

The trigger pulse conditioner circuit did not make any noticeable
difference.  It starts off with no misses, and after about an hour it
starts to miss... then slowly gets worse and worse.

A big box fan blowing on the unit did not make a difference. That's a
bit confusing, as it sure seems like a thermal issue. The trigger module
and large capacitor are both attached firmly to the unpainted metal case
of the unit, I guess that's how they designed it for heat transfer.  The
unit has a fan internally to move air around, but there's no actual
ventilation outside the box.  I can't quite tell if that fan is
working.  I'll try to test it separately.  If it is heat in some
component (which makes the most sense), it must be fairly thermally
isolated from the outside of the box.  Given that the thing works for an
hour before starting to fail... you'd think it would not be difficult to
maintain a thermal gradient large enough to prevent a problem. Weird.

When the unit was failing, and before the box fan was put in place... it
seemed slightly warm... but far from something you'd consider out of the
ordinary.  Once the box fan was on it for a while it seemed about the
same temperature as before use (almost cold), but it's performance
continued to deteriorate.  I forgot to actually use the thermal camera. 
I'll try that later to establish actual numbers there.

One interesting thing I learned is that the strobe unit is actually
powered ALL THE TIME, just like the PC that runs the pick and place.  I
assumed the strobe unit's power came on when the pick and place's power
switch was pressed... which is when the vast majority of the various
embedded systems are powered.  That tells me it is purely the power from
the strobe events themselves that cause the problem, and that the system
will go back to a more stable condition on it's own even under power if
the strobes stop for long enough.


I'm reasonably convinced it's the trigger module.  The random misses do
not make sense as a failure to meet a minimum charge, as the failure can
happen with any amount of wait before the strobe event once the unit has
started missing.  My favorite most-likely cause is a random arc-over in
the trigger module as Sean mentioned.  I actually have a little vacuum
chamber and some potting compound.  Still, how small is the actual
leak?  How much time in vacuum would it need to clear?  Maybe not long,
but possibly months/years.  Hmm.

It could also be the internal fan, somehow leading to arc-overs too.   I
can't quite picture how, but maybe.  It'd fit with the high apparent
thermal isolation of whatever is happening (if it is in fact thermal at
all).  I'll test the fan now.


I've bought a used replacement unit off ebay... perhaps it will work (or
donate a trigger module and that will work).  Thanks for the help
everyone.  I'll write further updates after receiving the ebay unit and
testing further (unless the fan turns out to be the culprit).


Darron

***@griffin.net

[a***@stfc.ac.uk]

Post by Darron Black
I'm reasonably convinced it's the trigger module. 

I believe you are correct, having got this far.

Post by Darron Black
The random misses do not make sense as a failure to meet a minimum charge, as the failure can happen
with any amount of wait before the strobe event once the unit has started missing.  My favorite most-likely
cause is a random arc-over in the trigger module as Sean mentioned.  I actually have a little vacuum
chamber and some potting compound.  Still, how small is the actual leak?
  How much time in vacuum would it need to clear?  Maybe not long, but possibly months/years.  Hmm.

You will not fix it, there may not even be a leak. My experience is that once this sort of thing happens you get localised carbon tracking with the epoxy carbonizing due to the effects of the arc. The original arc may well be a failure inside a component, e.g. the trigger coil, and then having started will slowly spread further.

Replacing it with the trigger module from the other unit is your best bet - unless that happens to have the same fault (hence why it is being sold). You may have to go back to the manufacturer to get a brand new trigger module.

[Darron Black]

Ah, of course.  That makes sense... I should have thought of that given
my exposure to issues someone had a while back with high voltage wiring
and mass spectrometer ion traps.  Once a unit started to arc, it was
quite hard to clean it well enough to prevent further arcing.

Yes, I'll skip the vacuum re-potting... I was unlikely to try that
anyway.  :)

Earlier this morning I ordered a trigger module as well.  (in Italian,
with google chrome's page translate options, I hope it actually gets
shipped)   Even if the new ebay strobe unit works perfectly, I'd rather
have a reliable spare.  ~$35 isn't too bad to give that a shot.  I could
have waited to see if the replacement strobe unit is bad but with a good
trigger module to donate... but this is dragging out enough already.


Darron

Post by a***@stfc.ac.uk

Post by Darron Black
I'm reasonably convinced it's the trigger module.

I believe you are correct, having got this far.

Post by Darron Black
The random misses do not make sense as a failure to meet a minimum charge, as the failure can happen
with any amount of wait before the strobe event once the unit has started missing.  My favorite most-likely
cause is a random arc-over in the trigger module as Sean mentioned.  I actually have a little vacuum
chamber and some potting compound.  Still, how small is the actual leak?
  How much time in vacuum would it need to clear?  Maybe not long, but possibly months/years.  Hmm.

You will not fix it, there may not even be a leak. My experience is that once this sort of thing happens you get localised carbon tracking with the epoxy carbonizing due to the effects of the arc. The original arc may well be a failure inside a component, e.g. the trigger coil, and then having started will slowly spread further.
Replacing it with the trigger module from the other unit is your best bet - unless that happens to have the same fault (hence why it is being sold). You may have to go back to the manufacturer to get a brand new trigger module.

[Darron Black]

Ah, I forgot to do an update email on the strobe unit.

I received the used unit from eBay, but it was a week and a half before
I ran the pick and place again.

I finally ran it all day (two such days now actually), and it hasn't
missed a single strobe that I can tell.  So, problem resolved.

I'll bet the old unit's trigger module is arcing.  I plan on checking
eBay for a replacement trigger module every once in a while to have a
good backup unit.


Darron

Post by Darron Black
Ah, of course.  That makes sense... I should have thought of that given
my exposure to issues someone had a while back with high voltage wiring
and mass spectrometer ion traps.  Once a unit started to arc, it was
quite hard to clean it well enough to prevent further arcing.
Yes, I'll skip the vacuum re-potting... I was unlikely to try that
anyway.  :)
Earlier this morning I ordered a trigger module as well.  (in Italian,
with google chrome's page translate options, I hope it actually gets
shipped)   Even if the new ebay strobe unit works perfectly, I'd rather
have a reliable spare.  ~$35 isn't too bad to give that a shot.  I could
have waited to see if the replacement strobe unit is bad but with a good
trigger module to donate... but this is dragging out enough already.
Darron

Post by a***@stfc.ac.uk

Post by Darron Black
I'm reasonably convinced it's the trigger module.

I believe you are correct, having got this far.

Post by Darron Black
The random misses do not make sense as a failure to meet a minimum charge, as the failure can happen
with any amount of wait before the strobe event once the unit has started missing.  My favorite most-likely
cause is a random arc-over in the trigger module as Sean mentioned.  I actually have a little vacuum
chamber and some potting compound.  Still, how small is the actual leak?
  How much time in vacuum would it need to clear?  Maybe not long, but possibly months/years.  Hmm.

You will not fix it, there may not even be a leak. My experience is that once this sort of thing happens you get localised carbon tracking with the epoxy carbonizing due to the effects of the arc. The original arc may well be a failure inside a component, e.g. the trigger coil, and then having started will slowly spread further.
Replacing it with the trigger module from the other unit is your best bet - unless that happens to have the same fault (hence why it is being sold). You may have to go back to the manufacturer to get a brand new trigger module.

[RussellMc]

On 25 January 2018 at 07:56, Darron Black <***@griffin.net> wrote:

​How hard would it be to abort the abort sequence if there was a trigger
pulse and no following flash?

Or to disable abort ability until you saw a flash following a trigger
pulse?​

Doesn't 'fix' the problem but stops it being one.


Russell

[Darron Black]

Russell,

If I could do that, I would have.  The pick and place (DIMA Dymaxion) is
pretty advanced for it's build date (2001-ish), but it's way past any
kind of software updates or so on.  I think I was updated to the "latest
and greatest" code which was dated 2005 if I recall.  They won't even
give me documents on calibration procedures, there's no way they'd let
me have any code to change to fix this particular problem or any other.

If I could do that, I'd LOVE to be able to change the code to use the
head cameras to check each feeder at the start (and after maybe 3 reject
picks on a particular feeder, or 100 picks, etc) and adjust the feeders
to center the parts.  The feeders have a nasty habit of "drifting"
slightly off center from the nozzle position.

I'd like to be able to use the fiducial cameras as a simple AOI system,
for that matter.  I know this system isn't 100% tuned (since they won't
give me cal procedures)... I'd love automated statistics on how far off
center parts placed with a particular nozzle averaged out to be, etc.

I'd love the system to keep track of failed picks per nozzle to identify
when a particular nozzle is probably clogged (with an 0402 part shoved
down it's throat, usually)

I'd love to make a nozzle changing station and code that up.  If I could
integrate nozzle swaps I could dramatically speed up assembly (halve the
time per board).  Right now, I keep a mixture of nozzle sizes on the
heads at all times to handle all part sizes and just live with it.

It's a pretty cool unit though... dual heads, 6 pneumatic and 1
electronic nozzles per head, 192 intelligent feeder slots, 7 cameras,
big tray tower... it's just a little too much like a beta product.  It
takes some effort to keep it on track.  The biggest problem is it can
barely manage 0402s, and my custom embedded Linux CPU board uses that
size extensively (250+ per board).  I have to spend about 5 minutes per
board nudging components slightly under a microscope before running them
through the reflow oven.  Actually, I've recently just started to let my
local CM do that board entirely.  I've still got 7 other (simpler)
boards to make, so there's plenty for this unit to do.

I've replaced the PC that runs it twice already, which was a significant
pain the second time around as it was impossible to reinstall one
critical third-party license.

I've replaced one camera that died within the first week.

I figured out the RS232-level protocol the intelligent feeders use and
documented it.  I was considering modifying one of the 6 feeder banks to
work with some other, more reliable brand of feeders.  The problem is,
I'd have to know how to run whatever other brand of feeders that is...
and I'm a bit stuck right there.  I could use maybe pneumatic feeders,
but that seems like a step backwards.

I'm also considering eventually reverse engineering the whole PC
interaction with the system and re-writing a new software platform from
scratch.

Really, I should be getting rid of this unit and buying a more capable
one...  I just can't quite bring myself to buy a reliable but "dumb" and
affordable system, and I can't justify wasting the money on a system
with this system's theoretical feature set.  I have a real interest in
automation (my other pet project is keeping the very old CNC controls on
my large-ish knee mill running) so it's really hard to part with.


Darron

Post by RussellMc
​How hard would it be to abort the abort sequence if there was a trigger
pulse and no following flash?
Or to disable abort ability until you saw a flash following a trigger
pulse?​
Doesn't 'fix' the problem but stops it being one.
Russell

[Denny Esterline]

<snip>

Post by Darron Black
I've replaced the PC that runs it twice already, which was a significant
pain the second time around as it was impossible to reinstall one
critical third-party license.
<snip>

Back about '99 I had responsibility for a couple of PC based industrial
systems that had "licensing issues".
The trick I used then - and may be useful to you now - was to "image" the
hard drive on the dying machine.
When I loaded that image on a new machine, I had to spend about three hours
getting windows drivers to
be happy with the new hardware (98SE at the time) but I had no issue with
the "third-party" stuff at all.

Of course, then I imaged it a second time so I'd not have to go through
that again. The replacement PC
I used was one of the standard office machines at that company. A
deliberate choice as it functionally
meant they now had about 20 identically configured "hot spares".

-Denny

[Darron Black]

Denny,

That was what I tried at first.  The new system was just too different. 
When I finally got the image to boot, I couldn't get the other hardware
to work for some reason.  I don't recall if it was the capture card or
the CAN interfaces, but something just wouldn't talk to the hardware
until I re-imaged and reinstalled the drivers.  I even did registry
diffs between the two images and tried to figure out how to go back and
fix the original image.... never quite figured it out.

It was the second time around.... the first time I think the image
worked fine (it was a much more similar unit).

Darron

Post by Denny Esterline
<snip>

Post by Darron Black
I've replaced the PC that runs it twice already, which was a significant
pain the second time around as it was impossible to reinstall one
critical third-party license.
<snip>

Back about '99 I had responsibility for a couple of PC based industrial
systems that had "licensing issues".
The trick I used then - and may be useful to you now - was to "image" the
hard drive on the dying machine.
When I loaded that image on a new machine, I had to spend about three hours
getting windows drivers to
be happy with the new hardware (98SE at the time) but I had no issue with
the "third-party" stuff at all.
Of course, then I imaged it a second time so I'd not have to go through
that again. The replacement PC
I used was one of the standard office machines at that company. A
deliberate choice as it functionally
meant they now had about 20 identically configured "hot spares".
-Denny

[RussellMc]

As well as all the other points suggested .... I'd think it possible that
the trigger voltage is not adequate or only marginally so for whatever
reason.

*[Manual here]
<https://media.digikey.com/pdf/Data%20Sheets/Excelitas%20PDFs/MVS-7000_Series_Manual.pdf>
1*

Fig 4 page 12 show the circuity as you describe it.
At the tube has only 2 terminals the controller must be generating a high
voltage (many kV) ignition pulse.
Marginal operation could be due to poor ignition loop impedance, trigger
module issues, failing tube (apparently eliminated).

Loop impedance appears to depend on C1 and/or CR1 deep-ending on pulse
polarity.

A look at trigger waveform and voltage could be informative (and exciting).
The waveform across CR1 may be an OK proxy.


Russell



1.
https://media.digikey.com/pdf/Data%20Sheets/Excelitas%20PDFs/MVS-7000_Series_Manual.pdf

[Darron Black]

Russell,

Thanks!  That's a good find.  I'll call Excelitas tomorrow to see if
they can offer ideas or quote a repair / replacement.

Weird that it's on DigiKey media storage, but I can't find it by model
number.  How did you find it?


Darron

Post by RussellMc
As well as all the other points suggested .... I'd think it possible that
the trigger voltage is not adequate or only marginally so for whatever
reason.
*[Manual here]
<https://media.digikey.com/pdf/Data%20Sheets/Excelitas%20PDFs/MVS-7000_Series_Manual.pdf>
1*
Fig 4 page 12 show the circuity as you describe it.
At the tube has only 2 terminals the controller must be generating a high
voltage (many kV) ignition pulse.
Marginal operation could be due to poor ignition loop impedance, trigger
module issues, failing tube (apparently eliminated).
Loop impedance appears to depend on C1 and/or CR1 deep-ending on pulse
polarity.
A look at trigger waveform and voltage could be informative (and exciting).
The waveform across CR1 may be an OK proxy.
Russell
1.
https://media.digikey.com/pdf/Data%20Sheets/Excelitas%20PDFs/MVS-7000_Series_Manual.pdf

[a***@stfc.ac.uk]

Looking at Figure 4 in that, the potted unit you were describing earlier I suspect is the trigger module.

I would suggest that the over wide pulse on the trigger input to the opto is causing the trigger module to overheat, and thus not firing the tube. Finding the reason this is too wide would seem to be the prime fault finding thing to do.

Post by Darron Black
Russell,
Thanks!  That's a good find.  I'll call Excelitas tomorrow to see if they can offer
ideas or quote a repair / replacement.
Weird that it's on DigiKey media storage, but I can't find it by model
number.  How did you find it?
Darron

Post by RussellMc
As well as all the other points suggested .... I'd think it possible that
the trigger voltage is not adequate or only marginally so for whatever
reason.
*[Manual here]
<https://media.digikey.com/pdf/Data%20Sheets/Excelitas%20PDFs/MVS-

7000_Series_Manual.pdf>

Post by RussellMc
1*
Fig 4 page 12 show the circuity as you describe it.
At the tube has only 2 terminals the controller must be generating a high
voltage (many kV) ignition pulse.
Marginal operation could be due to poor ignition loop impedance, trigger
module issues, failing tube (apparently eliminated).
Loop impedance appears to depend on C1 and/or CR1 deep-ending on

pulse

Post by RussellMc
polarity.
A look at trigger waveform and voltage could be informative (and exciting).
The waveform across CR1 may be an OK proxy.
Russell
1.
https://media.digikey.com/pdf/Data%20Sheets/Excelitas%20PDFs/MVS-

7000_Series_Manual.pdf
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