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Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Wed Nov 30, 2016 11:59 am
by Cliff S
To answer Andrews questions:
-15V: Uses a charge pump converter. See attached. Has a pretty high output impedance. Usually "-15V" can be in the -12.5- -14V range...ish.
See attached info on the other test commands.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Wed Nov 30, 2016 4:06 pm
by Rich Feldman
Hip, hip, hooray for Cliff. Very generous of you to share those official schematic pages. And the story about those pesky C149's. Good to know that my employer isn't the only one who sometimes traces reliability issues to product abuse by customers.
The charge pump IC for -15V reminds me of a new-ish class of components possibly handy in fusor labs. They're called photovoltaic MOSFET drivers, e.g. APV1121S or VOM1271. You put in about 10 mA and get an isolated DC source of more than 8 volts (with s/c current in the low microamp range). We have a design with 4 in series for 30 volt power to some "high voltage" CMOS analog switches. Might be handy for biasing certain radiation detectors whose average current is negligible.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 01, 2016 9:55 am
by Dan Knapp
Does anyone have a pin identification diagram for the CA11 connector? Does anyone know the derivation of the letter codes for the pins?
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 01, 2016 10:12 am
by Rich Feldman
The C,S,G etc are named in DXM manual somewhere, maybe even on short brochure which gives pinouts of all connectors.
Left two terminals are internally connected, and right two terminals are connected.
If you aren't using the filament supply, any single pin could be used for HV. No practical difference which side you choose.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 01, 2016 10:33 am
by Dan Knapp
I couldn't find the pin identifications in the DXM manual nor in the documents on the Claymount web page. I know they're all connected in the DXM in regard to the HV, but some people are planning to power a filament with these supplies. Does anyone know the historical derivation of what the letters stand for?
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 01, 2016 11:24 am
by Rich Feldman
Just learned that S and L are for Small and Large filaments, and C is the "HV output" according to
http://vjv.linx.netdna-cdn.com/wp-conte ... VG223k.pdf .
Same here from Spellman, in brochure for a line of bigger power supplies:
Now when there are 4 terminals, what's the fourth one called?If the letter is G then I bet it's for Grid, aka focusing cup or Wehnelt electrode. Okonite, a cable mfg, says:
Cable Core: Each Low Noise cable core contains two insulated filament conductor. In 65, 75, and 100kV cable filament conductors are #15 AWG (19x) [1.65mm2] tinned copper insulated with heat sealed color coded polyester tape. ...
Four conductor cables include one #20 AWG (7x) [0.52mm2] copperweld conductor per ASTM B-45 insulated with heat sealed polyester and shielded with metalized red polyester.
[edit] OK, my money is down on the table.
Small filament
Large filament
Common to both filaments
Grid -- for beam focus, could be 100 or 200 V more negative than the filaments.
From an early post by Andrew S:
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 01, 2016 4:02 pm
by Dan Knapp
The CA11 pin list from the DXM data sheet is reproduced below along with the wiring diagram from the DXM manual. They recommend a Claymount L3 cable as listed, but it seems strange to state that the "bare shield wire" would be connected to the high voltage. I think they must be referring to the bare inner wire which is one of the three conductors and not to the outer braided shield. I checked an old full size federal connector (3 pin) cable I have, and the braided outer shield is indeed connected to the chassis ground part of the plug as one would expect, with one of the three pins connected to the bare wire inner conductor. It must be part of the X-ray cable jargon to refer to the bare inner conductor as the "bare shield wire."
I still have found no diagram that identifies the positions of the C, S, L, and G pins on the CA11 connector; i.e. the relation between the 1,2,3,4 on the drawing below and C,S,L,G.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 01, 2016 4:08 pm
by Dan Knapp
I just looked again at Andrew's connector photo and noticed that he has the pins marked (the old eyes aren't what they used to be). So relating this to my drawing of the "CA11 socket":
1 = L
2 = G
3 = S
4 = C
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 01, 2016 9:26 pm
by Rich Feldman
Looks good, but I'd number the pins differently. Here's my take on it:
- csgl.JPG (40.8 KiB) Viewed 14101 times
A convention has persisted since vacuum tubes, including IC's in TO-cans, DIPs, etc., even modern packages smaller than vacuum tube pin diameters.
Pin numbering runs clockwise when viewing a socket from the wiring side, or a removable part from the pins side.
Counterclockwise when looking at a socket from the user side.
- tiny.JPG (25.91 KiB) Viewed 14024 times
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Fri Dec 02, 2016 5:04 pm
by Jim Kovalchick
Ran Andrew's DXM test on my unit. The xray on light comes on momentarily followed by the over voltage light. Any ideas?
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Fri Dec 02, 2016 5:44 pm
by Andrew Seltzman
The over voltage light should come on at the end of the test when voltage set is set to 0V and the output voltage is still decaying(due to it's RC time constant, and no load resistor). This is normal operation if the over voltage light only comes on at the end. Before that the output voltage should be tracking the set voltage on the graph.
Does it make a graph?
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Fri Dec 02, 2016 6:18 pm
by Jim Kovalchick
A single blank graph with no plot briefly appears. Then two blank graphs appear together. The graphs all disappear and an error message is displayed. "Vectors must be the same length. Error in => Spellman_DXM_control.m at line 137"
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Fri Dec 02, 2016 9:44 pm
by Liam David
I ran the functioning power supply with my fusor today and had some problems. I could turn the voltage up to 27kV, but plasma would not establish at any voltage around 15mtorr. Turning the voltage above 27kV got plasma to establish for a fraction of a second, but the over current light came on immediately and switched off the power. I use a 10-turn potentiometer to control the voltage and have the current set point at the max, but the over current light comes on regardless of how finely I turn the knob. Does anyone have any suggestions? I use a 6-way 2.75 conflat chamber, so Paschen's Law gives different values for my smaller chamber than the standard 6" chamber, but I've heard that other people with smaller chambers have had few problems in establishing plasma.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Fri Dec 02, 2016 11:09 pm
by John Futter
What value is your series limiting resistor in the HV feed???
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Fri Dec 02, 2016 11:41 pm
by Liam David
It's a 60k resistor, and operating it with vs. without the resistor seems to have very little effect.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Fri Dec 02, 2016 11:41 pm
by Liam David
It's a 60k resistor, and operating it with vs. without the resistor seems to have very little effect.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Sat Dec 03, 2016 12:47 am
by John Futter
OK 60K ballast resisator is a bit on the low side
When your plasma establishes it is better than a dead short so 27kV and 60K ohms means that the plasma is trying to take 0.45amps from your supply
i think that you will find that you will need to increase that resistor to keep from tripping the Spellman internals
try doubling it first if you can 120K
if it still does it double it again 250K
also make sure to limit capacitance from your Ballast resistor to fusor ie no coax (33pf /ft)
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Sat Dec 03, 2016 4:05 am
by Richard Hull
This is what I harped on in the limiting value of only 8.56ma on this supply in a posting above in this thread. 60k ohms is fine for a linear supply that has some beef in it. Raising the resistor value might do it, but the working dissapation will go up. The voltage drop would be not important, of course at most any value of ballast, but the dissapation would be.
Lets go figure........ assume you will need virtually all of that 8ma in a running fusor situation. Let's talk 7ma for starters on a working fusor. This will run continuously through, let us say, a 150k ballast.
7ma x 150k = 1050 volts across the resistor...No big deal voltage wise. .007 X1050 = 7-10 watts a good safety margin would demand a 25 watt resistor (would just get warm)
a 300k resistor would double that to about 50 watts. Such resistors are still sold. Just be aware that even at 7ma a large working ballast will dissapate.
This is the terror of a fast safety current trip on a modern switcher that is kissing the current limit for fusor operation to start with. This problem is probably just and operational one. Where there is a will there is a way. If I owned one of these supplies I would shunt the current sense resistor with a chunk of 12 gauge wire and be done with it! You would then become the slower acting human meat-engine trip circuit if something goes horribly wrong at the fusor load end. I have no idea how inherently weak or easily damaged the HV electronics would be to a 1 second half amp gas arc short.
Richard Hull
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Sat Dec 03, 2016 11:38 am
by Stefan Gustafsson
My supply is now fixed and up and running.
I had to replace:
RV2 - CL70 NTC Thermistor, burned
C149 - 33uf capacitor - visual leak
CR34 - MUR460 diode, shorted
Q10 - Mosfet, shorted, replaced with IPW65R110CFDA
Fuses- Two new 10A since I run it on 220V
I don't have a high voltage divider yet and can't verify it's output, but I can get it to fizzle of corona and arc if I turn it up too high.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 29, 2016 10:56 am
by Jim Kovalchick
I was not able to get HV out of mine even when applying manual control. I disassembled and closely inspected the board again. My board was pretty clean with no apparent over heating or other visible abnormalities except the top of C149 was slightly bulged so I replaced it. I wish I had a video of the power up. The fan and lights started normally but about two seconds later there was a loud pop and a smokey mist poured out of the vent slots. The new C149 had failed. There is no other damage. Any ideas?
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 29, 2016 2:45 pm
by Duncan Wilkie
Sounds like polarity was reversed, according to my limited experience.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 29, 2016 3:58 pm
by Richard Hull
Definitely sounds like installed in reverse. Trolyics don't like that.
Richard Hull
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Thu Dec 29, 2016 7:37 pm
by Jim Kovalchick
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.
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Fri Dec 30, 2016 2:53 am
by Richard Hull
I'm glad you got it up and running.
Richard Hull
Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.5
Posted: Sat Dec 31, 2016 4:51 pm
by Dan Knapp
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.