Spellman DXM70N600X3547 power supplies on ebay -70kV 8.56MA

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Duncan Wilkie
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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Duncan Wilkie » Thu Dec 29, 2016 7:45 pm

Sounds like polarity was reversed, according to my limited experience.
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Richard Hull
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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Richard Hull » Thu Dec 29, 2016 8:58 pm

Definitely sounds like installed in reverse. Trolyics don't like that.

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Jim Kovalchick
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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Jim Kovalchick » Fri Dec 30, 2016 12:37 am

You guys were right. That was reckless. Fortunately I ordered several new caps. I installed a new cap and dialed a low current demand and slowly ramped up a voltage demand of 1 volt or ten percent output. The pin out for voltage out followed along nicely. My next order of business is to build a proper control box, but for now I consider my power supply in working order.
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Richard Hull
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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Richard Hull » Fri Dec 30, 2016 7:53 am

I'm glad you got it up and running.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Dan Knapp » Sat Dec 31, 2016 9:51 pm

I finally gave up trying to make my DXM work and returned it. Although I was not happy that the vendor had listed these as working on eBay, Jon at NTC has been very cooperative. He even sent me another unit (marked "scrap") for spare parts to try to get one working. On my first unit, I was able to communicate via the web interface and could control the voltage up to 1400 volts. For any higher setting it failed. The spare parts unit had a blown fuse, which suggested problems on the PC board, so I tried the high voltage potted section with the PC from my original unit. I got the same results. I'm inclined to believe that both units have a failure in the potted HV section. Cliff had indicated that the ceramic capacitors in the potted section tended to fail when the units were operated in excessive ambient temperature. Although I have no way to know if the PC in my original unit was fully functional, I was definitely able to communicate with it. So if anyone is interested in a board that does communicate, the serial number on the communicating unit is 100785082-A00323. My guess is that Jon would be very amenable to an offer, since it is likely destined to be labeled "scrap" also.

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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Peter Schmelcher » Mon Jan 02, 2017 2:27 am

I suspect the failure mode of my non working unit went something like this.

1. High ripple current causes C149 to overheat, rupture, vent electrolyte, finally shorting internally becoming a resistor
2. Diode CR34 feeds C149 and with the fault current overheats and also becomes a resistor
3. The internal 24VDC supply that runs the DSP and other low voltage circuitry starts to drop
4. R218 a 0.05ohm 5W current sensing resistor overheats and cracks in half
5. The 24VDC supply collapses and K3 relay contacts open inserting inrush current limiter RV2 in series with the rectified 120VAC mains. This temporarily reduces the fault current
6. The fault current finally exceeds RV2 max continuous current. It heats up and cracks in half partially melting adjacent relay K3
7. The input full wave rectifier CR35 survives the fault current and the fuse finally opens
8. FET Q10 is destroyed (three leads get shorted together) while parallel component Q6 survives. An interesting failure transient. (FYI at lower output energy the DXM is fully operational on just Q6)

The two units I have are not identical. My older unit that arrived working was manufactured 23rd week 2013 and has a factory mod, see pic. My newer not working unit was manufactured 5th week 2014 and does not have the mod. The factory mod (and current design) puts a small restive load on C160 which reduces the ripple voltage/current on C149 (the issue is two separate 400VDC rails share one switching regulator). The two extra diodes in the picture are a belt suspenders plus rope kind of thing.
Factory mod.jpg
Without the factory mod the ripple was about 100V every 0.75 seconds. BTW you need a 120V line isolation transformer if you want to connect an oscilloscope and probe the power factor correction circuitry looking for problems.

Not having the parts for the factory mod I put a 1N4007 from C160 to C149. My mod seems to work fine and reduces the ripple to 0.5V at 120Hz when the HV output is off and disappears with any HV output energy. To be honest I prefer my mod but I will continue to keep an eye on it because “Only the paranoid survive”.

I replaced C149 with a higher ripple current capacitor (on both my supplies) that has over twice the original capacitor rating, Digikey 450BXW100MEFR18X35, it is physically taller and a tight fit for the available space. Electrical tape above the capacitor on the lid inside reduces any shorting possibility if the capacitor top should ever bulge.
new c149.jpg
I also replaced 4 questionably functioning parts K3 and CR35 and Q6 plus its driver IC in addition to the obviously failed parts. The total repair cost is about $40.

The two internal fuses will be replaced with one slow blow 5A and one fast blow 6 or 7A (lower values provide better component protection).

Lastly the service guy with not great eyesight (me) caused the problem in pic 3 requiring a scope to locate. The fix was simple just shove the wires into the connector…Doh
Open circuit.jpg
Have fun
-Peter

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Garrett Young
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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Garrett Young » Sat Jan 07, 2017 3:14 am

Andrew,

Are you willing to make and sell a C11 replacement connector to single conductor? I contacted claymount and they want $190 for p/n 12096 (recommended by spellman)
- Garrett

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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Andrew Seltzman » Sat Jan 07, 2017 5:22 am

That sounds way too expensive, can you send me the cad file of the cable they were quoting?

I don't have time right now to manufacture more connectors, though here is some ordering information

Ask for a quote on:
PN 14896, a 2m cable version should be $69.21
PN 10008 ring nut w/ r16 cutout should be $10 ea

I have ordered parts from claymount, it's generally straightforward to order with a credit card, they will want you to submit a purchase order to them, I have attached a template I used, It probably helps to have a fedex account number to give them to simplify shipping.
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Garrett Young
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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Garrett Young » Thu Jan 12, 2017 5:40 pm

Andrew,

They quoted $160 each and a 40 day lead time. (Also "Please note that the 14896 does already include 1 of the 10008 ring nuts in the hardware kit that accompanies the cable assembly. ") I've asked them to match the $70 price.
- Garrett

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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5

Post by Andrew Seltzman » Thu Jan 12, 2017 9:59 pm

Garrett,

that does sound weird, there was some variation between quotes on certain parts (one quote to me was $10ea for the ring nut, the other was $4) so they don't seem to have fixed prices, but such a large jump in price sounds unusual.
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