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Old 22nd July 2012, 02:56 PM   #3091
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aarghhh.... I don't have a suitable load resistor so can't test this Sunday. It'll have to wait until tomorrow.

Btw, PSUD2 tests it at 178V (which is too low for me, but still higher than I see when I hooked up the SSHV2)

Screen shot 2012-07-22 at 4.55.40 PM.png
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Old 22nd July 2012, 03:59 PM   #3092
Salas is offline Salas  Greece
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Did you have long non twisted wire between C3 and reg's input connector when you tested?
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Old 22nd July 2012, 04:02 PM   #3093
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yes, maybe 40cm
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Old 22nd July 2012, 04:05 PM   #3094
Salas is offline Salas  Greece
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Stick a capacitor across the input connector to decouple. Twist the wires if feasible. Also are your 100 Ohm gate resistors really near to the Supertex Mosfets gates and with short pin in your layout?
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Old 22nd July 2012, 04:32 PM   #3095
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Unfortunately didn't help.

I noticed, though, that I am able to trim both the CCS and the voltage between
-CCS: 95ma to 130ma
-Voltage: 127V to 111V



So I think the reg is working properly....
the gate resistors are within 1cm (or less)

Last edited by studiostevus; 22nd July 2012 at 04:38 PM.
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Old 22nd July 2012, 04:35 PM   #3096
Salas is offline Salas  Greece
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It helped, because you couldn't trim anything before. Your low input voltage thing is you need a different transformer. This one sags a lot and/or your coils are too resistive for 30mA CCS not to drop much voltage.
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Old 22nd July 2012, 04:45 PM   #3097
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You are probably right, but usually PSUD2 is quite spot-on:

I am using a transformer from a reputable source in Germany, multiple members have used it before without problems.

The chokes are specified by the same source as 330Ohm. I have modeled this correctly in PSUD2.

I did some further calculation, and think I could live with 170V input voltage (then I could have 150V output voltage which would work in my application). However I still don't understand this extreme sagging...
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Old 22nd July 2012, 05:02 PM   #3098
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Is the Tx internal resistance and chokes Rdc you feed to PSUD verified by measurement?
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Old 24th July 2012, 08:57 AM   #3099
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Salas, would there be any trouble using ~5-10cm wires from the Q3-spot on the PCB to mount the FET a little to the side?
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Old 24th July 2012, 09:14 AM   #3100
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Quite possibly, can't predict because it was never designed or tested like that. In any such a test I would move the gate resistor from PCB right at the pin (restore continuity at PCB also), hook scope on rail for oscillation stake out, and start at lower voltage if possible.
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