Help with Glassman 40kV, 15mA psu

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Rex Allers
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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.
642DB8E7-F3EE-4E22-9900-2343187E6B06.jpeg
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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
Fusion is the energy of the future....and it always will be
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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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2A84AF09-855D-4358-96C5-3D1F29FFEFFC.png
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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
Rex Allers
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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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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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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Hi John,

I just got done testing the diodes via voltage drop in forward/reverse mode. Didn’t measure current, is that critical? There were 6 that measured 20v in the forward direction and one that had a small burn spot underneath, but read around 14v like the rest. Would you be suspect of these higher forward voltage drop diodes, or leave them be?

As for any bad capacitors, they all measured 2nF or 4nF if paralleled up. Any other way to test?

Before I button it all back up, would there be anything to gain by applying a low AC voltage to the input and probing around with a DMM?

I feel like I’m running out of gas :-(
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Looking at the data sheet for the 2CL2FM (Chinese diodes that are essentially the only option out there), these are rated for 20kV, 100mA, and 100nS. They have a max forward voltage of 35v, so it seems that 20v on the 6 outlier diodes may be okay?

If this is the case, and my two shorted diodes were the only diodes that failed, then there must be a capacitor that tests okay (capacitance that is) that is fouling things up? Or, could there be a problem with the board itself? Maybe it’s conducting somewhere?

My last suspicions with the multiplier board is that I upset things by completely removing those two chokes and the two failed spark gaps?

I almost feel like just rebuilding the entire board using those Chinese (ugh) diodes and some new capacitors…It would be $$$ but far less than a new (used) one.

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

Post by Finn Hammer »

Matt,

Nothing to (ugh) about. I use the 30kV variety of those same diodes, and they perform flawlessly. Just don't go beyond 50kHz, or they will overheat.
There is a lot of badmouthing, regarding chinese products, but the truth is, even brand name products come off chinese production lines. The lead glass, the quarts glas, the bell jar, the capacitors, the diodes, the pcb, all in my fusion endevour, comes from China. Even my old Tektronix scope had Made in china labelled on it. Just use your sense when buying.

Cheers, Finn Hammer
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Hi Finn,

Looking over the PSU PWM chip data sheet, and the r/c values chosen for the PSU, it looks like it runs right at 50kHz, so I may be stressing them a bit. I might need to tune it down some.

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

Post by Richard Hull »

Assuming some forethought on the part of Glassman in designing the multiplier and the caps used therein, tuning the frequency down could affect the ultimate HV level and the ripple factor. You might not blow anything up but tread carefully.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

Yup, I thought of that…I might just risk it seeing as I can’t go for more than 10-15min per run.

This is assuming that I can even get this thing back up to its former glory.
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Richard Hull
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Re: Help with Glassman 40kV, 15mA psu

Post by Richard Hull »

I have said this before. Manufactured supplies, (Spellman, Glassman, etc.), when run to or near their full stated limits, voltage and current wise, with our particular, rare and unusual gas load, are at peril. Our gas load can oscillate at HF frequencies and or bump during operation in a manner that the manufacturers design team might not figure on and why should they. Their mission is to design a ripple free, pure DC supply capable of suppling a resistive load which might have a few rare spikes in it. This is why they have current limit cutoffs in protection circuits in many such supplies. Their output voltage has no real energy backup due to the multiplier capacitive limitations and the high impedance of the original, smallish HF feed transformer. These supplies, due to their work-around over the old 80lb iron core, low frequency transformers of old, are necessarily electronically complex and running their components to a calculated level right at the edge of their engineering capacity with some acceptable margin for safety and longevity.

I am not saying they are weak or relatively worthless, but most of them are found to be pushed right up to their limit with non-designed for loads by those using them here at fusor.net. Now, if you buy or obtain a Glassman 60kv supply that is rated for 50ma, that is another matter. 50kv at 20ma into a fusor would not peck at the lobes of its extreme limit. It is operated well within its design parameters.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Help with Glassman 40kV, 15mA psu

Post by Matt_Gibson »

I hear you, Richard. Unfortunately, outside of building something, it’s my only option. There aren’t any suitable transformers anywhere anymore. I may wind up having to just replace diodes and capacitors with higher rated components as they fail…
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Re: Help with Glassman 40kV, 15mA psu

Post by Richard Hull »

It is rather sad that the fusor's power requirements to do good fusion strain at the limits of modern technology and more importantly at the purse strings of those who would do amateur fusion to a largely successful degree. This for those who are not well funded or well versed in high voltage, high power systems, is a big issue. Those who persist are the real winners here.

I would focus on the diodes. Ceramic capacitors do not like HF filtering at real power levels. We learned this the hard way in tesla coiling at oscillation energies of 400 watts and above. The silver plating on the ceramic knob body sides gets blown away internally. The capacitance drops and often the main contact to the coating is often blown clear of the flat contact and internal arcing occurs at a level not easily detected. In a string of capacitors this starts a down hill run and stress on the rest. Ceramics are best used for filtering at lower frequencies to DC. If rather large oscillatory power is expected at high voltages, polypropylene is preferred, but commands large volumes at required high voltages per unit capacitance. Paper is also good with some loss. Mylar is very high loss at HF and high power.

Good luck

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

Post by John Futter »

Check with a resistive load
does it provide full current??
if not
Suspect caps
these have to be tested at elevated voltage close to their max rating

As I said previously the diodes should work with 3 or more pp9s in series with suitable resistor to get say 50mA
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