Help with Glassman 40kV, 15mA psu

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Matt_Gibson
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Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Hi everyone, I hope this post is appropriate and that this is the correct place to ask.

I managed to pick up a 40kV @ 15mA Glassman EW series for $200 on eBay. First, I powered it up (after zeroing the dials) and it comes on, fan, and all lights. Looks like the basics are good.

Next up, I opened it up to take a look. Very dirty/dusty. I used a can of air to remove the easy stuff. I see that the multiplier section is covered in black soot. I don’t see this soot anywhere else, but now I’m curious as to the state of things inside.

Before I start tugging and pulling, has anyone have any experience with removing the multiplier section? I see some connects that can be removed, but the flyback transformer seems to be hardwired to the multiplier. Being that this is a positive psu, I’ll need to remove this multiplier anyways to reverse the diodes…

Next up, I don’t have a hv cable for this. I do have some 42kV dc conductors, but have no idea how to safely attach them into the HV out connection.

The mA meter isnt zeroed. I tried to adjust the adjustment screw and, while it moves the needle, it doesn’t zero. Am I doing it wrong? :-) Or, is my meter toast?

Finally, before I start the arduous process of reversing the diodes, I’d like to test this psu to make sure that nothing else is wrong. Any tips other than not drawing arcs?

Thanks!
Matt
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Joe Gayo
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Re: Help with Glassman 40kV, 15mA psu

Post by Joe Gayo »

The red wires from the multiplier to the vertical black plastic support, just pull out of the black plastic side (the red wires have a pin, soldered under the heat shrink, and the black plastic piece has molded in sockets that the delicate secondary transformer wires are attached to).
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Hi Joe, you beat me too it. I figured it out after getting a little brave :-)

So I see that the multiplier is absolutely filthy. What could this be from? Is it the HV field attracting mess over the years? I have my work set out for me as far as cleaning goes…
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Re: Help with Glassman 40kV, 15mA psu

Post by Joe Gayo »

The strong electric field within and around the multiplier will certainly collect dust/particulate. Maybe it was used in a dirty environment or potentially components failed.

I ultrasonically clean all my boards using electronics grade IPA.

Good luck.
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Okay, so I have a problem. When I turn on the supply, the HV light is lit before I press the button for it. Pressing the button doesn’t seem to have any response. Following the manual, turn on should have this light unlit….

No output either. I have confirmed that the 0-10v for both current and voltage local control track the front control knobs and that everything is jumpered per the manual.

When inserting a power cable, do I need to push back on the spring to active a switch or do I just need to make contact?

:-(
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Re: Help with Glassman 40kV, 15mA psu

Post by Joe Gayo »

If by "power cable", you are referring to the high voltage output cable then there is a spring in the multiplier but it's there to ensure contact not activate a switch.

You probably need an oscilloscope to troubleshoot.
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Yes, the HV cable.

I am printing out the schematics so that I can see where the HV activate and HV present light are tied in. I do have a scope, but no diff probe so limited in what I can do.

Discounting the HV activate jumper on the back doesn’t affect the HV present light on the front. Seems like something in the logic is bad. This may wind up being a parts psu…

Dern.
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Figured it out! After days of poking around inside and looking over a manual that I found online, I found a pin with “TTL” tied to the “enable” logic that wasn’t mentioned anywhere in the manual. Traced it out to a BNC connection on the back. Applying the built in 10vdc reference to this pin instantly brought this thing to life!

I’ve only been able to test it to 10kV because I need a more capable dummy load.

There’s still a few bugs to work out:
1-The HV on button function doesn’t do anything. Power up of the device also enables the HV without the switch being pressed.
2-The current analog meter is sticking. It’ll max out at 15mA, but is jumping all around in between 0-15mA.

Other than those two minor things, it looks like I got it working. Now I need my solder sucker to arrive so that I can reverse the diodes to make this a negative 40kV at 15mA supply.
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Re: Help with Glassman 40kV, 15mA psu

Post by Rex Allers »

I just saw this post. Sorry I missed it earlier, I could have helped with that back panel BNC enable.

To change polarity, in addition to reversing the diodes in the multiplier, you need to change some soldered jumpers near the edge connector in the multiplier.

There was a great old post on doing this. I just checked and it was one that lost all its attachments. I had saved local copies and have editing permissions, so I fixed it.

"Reversing a Glassman Multiplier" (2007)
viewtopic.php?f=11&t=4622#p27460
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Re: Help with Glassman 40kV, 15mA psu

Post by Rex Allers »

Also, here's a paper I wrote about making an HV output cable for Glassman supplies.
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Re: Help with Glassman 40kV, 15mA psu

Post by Rex Allers »

On the polarity jumpers in the HV Multiplier that need to be changed to reverse polarity, here's an image I put together for the multiplier in the ER supplies.
HV Polarity Jmprs.png
You have an EW supply. I'm not sure if the locations are the same as the ER but I think the 'W' names are the same. So for your initial positive configuration there should be two soldered in, W3 and W5. To convert for negative those two are removed and W1, W2 and W4 added.

To verify where they should be installed, you should be able trace out the EW circuits using the multiplier schematic pdf in the old post I linked to in an earlier message.

--Edit--
I looked at one of the pics in the 2007 post. I cut out the section with the jumpers. Looks like it shows the three jumpers for Neg configuration. I added 'W' labels for the three installed jumpers.
EW Neg jumpers.jpg
The W2 placement looks different than in my ER picture but I suspect it is functionally the same connection.
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Richard Hull
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Re: Help with Glassman 40kV, 15mA psu

Post by Richard Hull »

Well done on the PDF!

I was lucky and just poked a length of 30 kv anode wire, no shielding, into a plexiglass plastic tube that fit the hole and soldered, then epoxied, a simple "banana plug" at the end. This was for my nice rack mount, variable 30 KV glassman rated at 2ma. I use it for electrostatic demos. It cost me a buck at the scrap yard here many years ago. I think most every one here in our local HEAS group got one as the word spread that there was a stack of them down at the "yard".

Of course, I had no need to reverse the polarity as my low current supply is worthless for fusor work. It tends to drive electrostatic motors for demos and disectable charged capacitors.

Richard Hull
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Rex,

Thank you very much! I reversed the diodes before seeing this reply, missed swapping the jumpers around, and had a whoopsie. A lot of bangs and flashes while my dummy load was smoked.

My guess is that the driver isn’t getting proper feedback and is running full bore?

Hopefully I didn’t damage anything. I looked over the HV board and all looks/smells well. It was arcing/flashing over the resistors when I cut power, so maybe it’s okay.

I’ll fix those jumpers tomorrow! Gonna be a long day at work obsessing over this :-)


Edit: Swapped the jumpers and the negative led is now lit and NO MORE POPS (arcing) from the cw multiplier!!!!

I was able to test controls on some Hv resistors and found that they work as expected again.

Now I guess it’s time to get going with the vacuum side of things.
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Okay so I had a failure. Looks like the over voltage protection spark gaps blew. The PSU seemed just fine and continued feeding the fault…I could smell the board burning which is why I bothered to look.

How necessary are these things? Any harm in just taking them off, cleaning up the board, and then getting back to it? I don’t see them in other multipliers that I have or have seen.
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Richard Hull
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Re: Help with Glassman 40kV, 15mA psu

Post by Richard Hull »

I think you got an inductive kick from those chokes that arc'd the gaps and thing went down hill from there. Those gaps are across the chokes. Pull the gaps out and the chokes are out of the circuit. I do not have the schematic of this circuit and suggest you tread carefully.

The issue is, the fusor is a bumpy and non-smooth load. Oddly, Glassman designed this as a stable DC supply and expected the user to need a stable, regulated DC HV load. You kinda' don't have that, so all bets are off where they are concerned. You get current spikes in the supply especially as the plasma strikes or at any time you see the plasma flash brighter to dim and when it goes out and immediately comes back on.

This is why a homemade supply assembled by a very knowledgeable electronics person is often to be desired. Many knowledgeable people in electronics, ever engineers have zero knowledge in high tension DC supplies and even less knowledge in HV DC supplies that have to feed terribly bumpy DC loads. One saving grace is that the fusor has little need for tight DC voltage regulation, A full wave 60hz, unfiltered High voltage is just fine for a fusor. I can't speak to a high frequency HV system of similar nature. Perhaps just a simple doubler, tripler or the like would do the trick at high frequency. So much here depends on the load experienced and the wide separation of components in the system. These are often better floated in air than mounted on circuit boards or even on what seems a suitable plastic.

The board is burned and you can't effectively clean it up now. Two options. Remove the chokes and gaps or create a small, new floating board with those components on it. Your choice.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Hi Richard,

I drilled/sanded/99.9% alcoholed out the utter mess and think it came out okay. I’ll bypass the chokes for how to see what happens.

Edit: Update, it works and no more old computer smell (burning board). I’m guessing that my ballast resistor just become a lot more useful?
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Re: Help with Glassman 40kV, 15mA psu

Post by John Futter »

Glassman put those chokes in as dV/dt limiters during output flashovers to earth and the spark gaps are to protect the chokes from arcing over during OTT events

all of this to protect the capacitors in the multiplier string -nearly all glassmans i have repaired have had shorted or partially shorted or worse caps that short at half their rated voltage. enough damage and you also take out the odd diode

a properly sized ballast will stop this damage
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Re: Help with Glassman 40kV, 15mA psu

Post by Rex Allers »

Note: I just read John's concise message that was posted while I was writing. All sounds good except I think he meant dI/dt.

-----
Here's my longer reply...
Matt, that's a bummer.
Question: Did you ohm out the two inductors to ensure neither is open?

You said it is working after your surgery to cut out the two smoked arresters, but I could conjecture that even if one L was open it could appear ok with a tiny arc feeding the output. If so, maybe more smoke to come.

Here's my take on that output circuit. The two inductors are in series and are in the HV output path. They must be there to provide a bit of filtering on any current transients in the output. If the current tries to change rapidly the inductors will try to smooth that out but that will also cause a voltage induced across them. Big enough current rate of change (di/dt) and you could have a lot of voltage across the coils which could short or open them out.

So to protect the inductors they have a gas discharge arrestor across the inductors. In your case two GDTs in series that are then in parallel with the two series inductors. The gas discharge tube has a specified trip voltage. When that is reached an arc starts in the gas of the tube which essentially makes it a short. That short bypasses any current through the inductors which should let the voltage across them drop and kill the arc through the arrestors. So back to normal (we hope).

From your pic of the smoked board it looks like the smoked arresters are EPCOS 800V devices. So with two in series 1600 V to light them up.

I recently got a Glassman EK supply 600 W output 30 kV, so similar specs to your EW. I still had it apart to work out details of what's in there. So I looked at the multiplier section. I see a similar output. In the output there is just one inductor in series in the HV output. This one is in a clamshell ferrite core 1" dia x .625" high. Probably around 200T in the coil. Across it is just one EPCOS 800V arrester. Same general idea.

Here's a link to the (TDK) EPCOS page where you can download publications if so inclined,
https://www.tdk-electronics.tdk.com/en/arrester

and here is the probable datasheet for for the part in both of our units,
https://www.tdk-electronics.tdk.com/inf ... 40xxxx.pdf

So what went wrong for you? Something caused the voltage across the two inductors to reach around 1600 V. The arresters fired, shorting to the output load and also across the inductors. One would expect the inductors to pretty quickly stabalize, dropping the voltage across the arrestors and quenching them off.

One of the EPCOS documents says this:
"The follow current must be limited so that the arrester
can be properly extinguished when the surge has
decayed. The arrester might otherwise heat up and
ignite adjacent components."

From the resulting burned areas, either your arresters never extinguished or they kept re-firing which kept them on too much of the time.

An open inductor could do it. Some sort of oscillation keeping repetitive current spiking from the load?

I think you mentioned a ballast resistor in the HV path. That was going to be one suggestion I might offer. A high wattage resistor somewhere in 50 - 200 K ohm range might help tame things.

With your arresters that burned up cut out of the board your inductors have no protection from induced voltage due to current transients. You might be better off if you just bypass the the inductors or replace them with resistors (see ER supply below).

Some other thoughts... Do you know if the output current limit of the supply is working? Do you have a dummy load? If so, turn down the current below the steady state of the load at a certain voltage and insure that reducing the current setting drops the output.

So these are just some of my ideas speculating from theory. Maybe someone else has other thoughts or experience from real world applications.

One last thought, the Glassman ER supply HV section, which is what Joe Gayo used in his original experiments have a similar output but no inductors, rather two 27K resistors in parallel with a GDT arrestor. That was also the same 800V device, I think. Note: Joe didn't use an actual ER supply, but the same ER HV multiplier module with his own driver circuits.

Here's the ER supply HV multiplier circuit:
60KV HV Schem.png
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Re: Help with Glassman 40kV, 15mA psu

Post by Rex Allers »

For John if you are still reading.

You mention repairing Glassman supplies with bad caps.

Do you have a vendor you find trustworthy for the sort of big blue caps one finds in HV sections of Glassman supplies?
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Thanks for the replies everyone!

A few answers to questions:

I didn’t ohm out the chokes, but they looked “okay” as in nothing obviously wrong with them. I’ll check them out when I get home, today. Interestingly, both the spark gaps tested open circuit. I had assumed that they had failed short circuit.

This happened while testing the fusor. Perhaps the spark gaps were “tired” and gave up the ghost during a plasma start/stop? I have been using a 50kOhm ballast resistor the entire time while testing this with the fusor. Maybe 50kOhm is too small?

I think that the current and voltage limit circuits work. Setting the current for “3mA” won’t let me get passed this no matter how high I try to push the voltage. Same for voltage limit. The control lights will also light up when one is exceeded.

Any off chance that me converting this to negative could have buggered something?

Should I rely on the ballast or should I be looking at getting some new spark gaps? I don’t want to destroy this thing :-)

Edit: I think that I know what caused this. Back when I converted to negative, I totally missed that I had to reverse the jumpers. This caused ALOT of arcing and popping from inside the multiplier…My guess is that the PSU went berserk and wore these little guys out!

-Matt
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Re: Help with Glassman 40kV, 15mA psu

Post by John Futter »

I bought real Murata caps 2n2 15kV from memory
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

So I decided to move my power supply issues back over here rather than to clutter up my other thread.

Quick rundown of the problem: At higher voltages, my psu drops current down significantly. This has been getting gradually worse over time to the point where I couldn’t maintain even 1mA.

I did a quick and dirty check of the multiplier and found two shorted diodes. I was able to use my Dmm on these two diodes because they were shorted (or so I guess is the reason)…Replacing these two made an immediate improvement, but not back up to snuff. I’m now able to push 4mA at 40kV. I should be able to push 12.5mA.

Thinking about things, I realized that more diodes are probably bad and have failed open circuit such that my Dmm isn’t going to be useful. My question is, is there a way to test these diodes without removing them? Or will they need to be removed before connecting to a higher voltage supply?

While I don’t have a perfect understanding of CW multipliers, I would guess that bad diodes would definitely cause these issues and NOT one of the various protection circuits.
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Bob Reite
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Re: Help with Glassman 40kV, 15mA psu

Post by Bob Reite »

Bad diodes will cause low output for sure. To be sure of you test results, disconnect one end of the diode under test.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

9 stages times 4 diodes per stage…Ugh.

Be back in a few days :-)

Edit: Quick check. Reverse direction reads supply voltage (27.5v) while forward direction reads somewhere between 14-16v for all of one side, save for two diodes. Those are both reading 19v in the forward direction. Would these two diodes be bad? Or just that they have a higher forward voltage than the others?
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Re: Help with Glassman 40kV, 15mA psu

Post by John Futter »

3 x pp9 batteries in series (with a resistor to set current to 10mA) with an ammeter in circuit to test each diode in circuit

still think you have some mortally wounded caps in the chain
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