reversing polarity of a Glassman model LT from P to negative

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John Griessen
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reversing polarity of a Glassman model LT from P to negative

Post by John Griessen » Mon Sep 30, 2019 6:24 pm

I've got my diodes flipped, but am not sure about the jumpers of the HV module to flip the metering...
and the manufacturer is no help:

"I’m sorry but the model you mentioned is one we manufacture for an OEM Customer and due to our agreement with that customer, we cannot provide documentation, repair, or support modification of the power supply.

Best Regards, S______ Sales Manager XP Power LLC XP Glassman High Voltage"

Does anyone have a schematic for this model, or any LT HV module similar to it?

PS/LT040P050XX0
ser no. M820409-02BP960401

The HV module is:
AHV1LX040P50XX0

i want to change the jumpers for negative operation.
I already changed the diodes.

Thanks,

John

Rex Allers
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Re: reversing polarity of a Glassman model LT from P to negative

Post by Rex Allers » Tue Oct 01, 2019 10:56 am

I have accumulated some Glassman info. Not on the LT but it could be similar to others. Got a pic of your LT multiplier section? Overall, and a pic of connections might help populate the knowledge.

I have found the basic instruction manual as a pdf. No schematics and not this level of detail, but I could share if you haven't found it.

No direct knowledge, but I have other Glassman HV section info that may be similar if you are able to hack your circuits.
Rex Allers

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Re: reversing polarity of a Glassman model LT from P to negative

Post by Rex Allers » Tue Oct 01, 2019 11:42 am

PS

That's a lot of work to reverse all the multiplier diodes. Hope you kept their blobby soldering style. All that excess solder is there to make a rounded shape to reduce any sharp peaks that could induce HV arcs.
Rex Allers

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Bob Reite
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Re: reversing polarity of a Glassman model LT from P to negative

Post by Bob Reite » Thu Oct 03, 2019 2:38 am

If you look back at my archive "build phase" messages, you'll see the commercial 8 stage CW multiplier. It came as positive output, "As is". I used the opportunity while reversing the diodes to test them. All were good. Not that much work as this came apart easier than expected at first glance.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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John Griessen
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Re: reversing polarity of a Glassman model LT from P to negative

Post by John Griessen » Mon Oct 07, 2019 12:36 am

I have other Glassman HV section info that may be similar if you are able to hack your circuits.
Yes, similar models would be helpful in figuring out the metering jumpers.
Hope you kept their blobby soldering style
Yes, I preserved that when I reversed the diodes.
I used the opportunity while reversing the diodes to test them. All were good.
I tested the overall function of the supply before taking the HV section apart, but did not test diodes separately,
just handled carefully and cleaned flux well with isopropyl 95%.
glassman-lt-2kW-40kV-HV-multiplier-08-sm.jpg
metering jumpers on Glassman LT HV mult section (PCA1271 rev A)
Attachments
glassman-lt-2kW-40kV-HV-multiplier-03-sm.jpg
Glassman LT HV mult section (PCA1271 rev A) bottom view
glassman-lt-2kW-40kV-HV-multiplier-02-sm.jpg
Glassman LT HV mult section (PCA1271 rev A) top view
glassman-lt-2kW-40kV-HV-multiplier-14.jpg
Glassman LT HV mult section (PCA1271 rev A) edge view

Rex Allers
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Re: reversing polarity of a Glassman model LT from P to negative

Post by Rex Allers » Wed Oct 09, 2019 8:30 am

John,

Thanks for the pics. I haven't seen a Glassman HV multiplier section that looks very much like that before.

Main thing that I'm looking at is your 3rd pic (top view). Although new to me, the general scheme seems to make sense. The lower right quadrant looks to be the multiplier section. I assume this is where you swapped the diodes.

The thing that puzzles me is that the lower-left and upper-right quadrants in the pic seem to both have HV divider sections. These are both (I assume) 4 blue high value resistors in series (with caps in parallel). These are both familiar configurations for sensing the HV output, but I really do not understand why there are two of them, separated by what look to be some series (spike snubbing?) resistors.

That's not a configuration I have seen before. I don't understand why there are two. A HV sense of current via a difference across those output resistors? I don't think that is practical and it is much easier to sense current on the input side, which is where other supplies I know of do it.

So I don't know. Other supplies that I have seen have the HV input (to the multiplier), typically high freq and two 5 KV phases relative to gnd.

Then on the signal connector, these:
a gnd ref
a voltage proportional to the current into the common of the multiplier
a voltage proportional to the HV at the output
possibly a jumper to represent the polarity

In configurations I have seen there may be different return pins for + or - current sensed.
It may be necessary to add a new resistor to the input sense of the current for the alternate polarity configuration.

So I don't really know and don't understand the why of the two dividers in your pics.

The Glassman supply I have looked at closest is the (mere) 300 W ER series, I can share schematics for that which I have annotated with my observations. But there seem to be big differences in this multiplier. Let me know if you want to see that ER stuff and I'll look for a link.

It might be really hard to guess what the signals are (need to be) without schematics of the main unit circuits or someone with more direct experience.
Rex Allers

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Re: reversing polarity of a Glassman model LT from P to negative

Post by John Futter » Wed Oct 09, 2019 8:39 am

I have an 80kv glassman at work that is reversable ie you take out the HV multiplier stack in the white plastic box and exchange it for the other polarity box, the pcb in the multiplier section does the reversal not the main board which is common to both.
Looking at the multipin connector thats connects the HV box to the drive electronics differing pins are in use between the two

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Re: reversing polarity of a Glassman model LT from P to negative

Post by Rex Allers » Wed Oct 09, 2019 7:38 pm

John F,

Yes, the white plastic box is the HV multiplier section. Swapping it is the usual way to switch between P and N polarities. The ones that were shipped with two multiplier sections have an R in their part number where P or N is in the normal single polarity versions.

A P multiplier can be converted to N with lots of soldering to reverse multiplier diodes, more soldering to change jumper wires, and possibly adding a different current sense resistor.

The pictures that John G has shared are of a large multiplier board that is the equivalent of the white plastic box on other supply versions.

I've seen some of the white box versions but never one like this style. I mentioned one thing that puzzles me about this design (the two HV divider sections). It is all guess work, about how to finish the conversion, unless someone can provide informed information about this design of multiplier.
Rex Allers

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John Griessen
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Re: reversing polarity of a Glassman model LT from P to negative

Post by John Griessen » Thu Oct 10, 2019 12:37 am

It is all guess work, about how to finish the conversion, unless someone can provide informed information about this design of multiplier.
Yes, I was hoping to find someone with schematics, since the company now refuses to divulge old schematics.
Glassman HV was bought out is why they refuse.

Next is tracing the parts to create a schematic -- reverse engineering it. After seeing what the metering jumpers connect to as is,
I can see if it would survive turn on as is, or with jumpers removed, then figure out some safe experiments to try. It was a working machine as positive. Now I am a little stuck since HV is not so easy to experiment on -- needs that white plastic box on every time it is run up...

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Re: reversing polarity of a Glassman model LT from P to negative

Post by Rex Allers » Thu Oct 10, 2019 10:33 am

John G,

So from what you said last, I think your supply has a white plastic box around these boards too? If so, could you share a pic of that -- just to improve my knowledge of what's out there.

Lot's of Glassman stuff seems to share common design configurations. I'll share some info on a HV multiplier section from another supply I've gotten pretty familiar with. It won't match, but maybe there are similarities that can help you hacking what you have.

Back around the beginning of the year Joe Gallo shared a supply that was being sold on ebay. I recognized the parts as looking like a Glassman ER supply. What Joe had was just the HV section. I checked with the seller and got a couple with both the HV box and the main circuit board. Indeed it was an ER supply but deconstructed in a custom configuration for a particular application.

The ER supplies are rated for 300 W output. In this case it was 50 KV at 6 mA. I had a manual from the web that gave the ER schematics. I edited the HV multiplier page to match what I found in this version and also added some annotations that attempt to explain some details.

Here's a link to a zip with stuff I put together about the HV output part of this device.

http://www.xertech.net/pub/er-hv-info.zip

The aluminum box in one pic is for this custom version, not the normal ER bench supply. The white HV multiplier in the box is a standard one for any ER supply. This white box is about 5" wide by 14" long.

On the schematic of the HV multiplier, the HV is sensed by a string of high value high voltage resistors (R3-n). In yours it looks like there are two such divider strings. As I mentioned, I don't understand why two dividers on yours.

So not a close match, I'm sure, but maybe looking at my schematic for the current sense in the two polarity options and how the jumpers are configured between polarities, might give you some clues in hacking your device.

Feel free to ask any questions on this. Please let us know if you figure any details out.
Rex Allers

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