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Help for PMillett HV regulator
Help for PMillett HV regulator
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Old 30th December 2017, 05:15 PM   #1
crazyfrog is offline crazyfrog  Canada
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Help for PMillett HV regulator
Default Help for PMillett HV regulator

High Voltage Regulator

Hi. I have the Pete Millett HV regulator board and something is wrong. It looks like current flow isn't correct in LM317.
With R4=10k and R5=120R (RV1=0), voltage should be 105V @ 34mA but this is what I get: input=140V, Vout=130 with a resistor load of 3,12k.

Specific parts:
Q1: IRF840
U1: LM317 (not HV version)
C1: 33F
R6: 3.6R

Readings:
Vgs=3.7V
V(R7)=5.4V (meaning 54mA)
LM317 (in-out)=1.6V (should be around 15V)

Suggestions? Thanks

Note: I used PM reg in another application at higher voltage and current and had no issues. LM317 was HV version. Just had to reduce R7 value a bit.
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Old 30th December 2017, 05:43 PM   #2
leadbelly is offline leadbelly  Canada
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Looks like D5 might be your issue. What did you use?
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Old 30th December 2017, 05:54 PM   #3
crazyfrog is offline crazyfrog  Canada
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Help for PMillett HV regulator
P6KE39A

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Originally Posted by leadbelly View Post
Looks like D5 might be your issue. What did you use?
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Old 30th December 2017, 06:00 PM   #4
leadbelly is offline leadbelly  Canada
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Then I would try it into a much smaller load resistor. If you can get a big enought drop over the LM317 it should start regulating.
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Old 30th December 2017, 08:27 PM   #5
crazyfrog is offline crazyfrog  Canada
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Help for PMillett HV regulator
I don't know what you mean by "much smaller" but the real load should draw 36-38mA. I tried 2.5k but Vout is just a bit lower (126V).
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Old 31st December 2017, 05:12 AM   #6
leadbelly is offline leadbelly  Canada
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I would check all the voltage drops over all the resistors to make sure current isn't getting around the regulator.
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Old 31st December 2017, 02:51 PM   #7
pmillett is offline pmillett  United States
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I assume that you've checked for all the obvious things (open solder joints, backwards diodes...)

Normally I would expect that this means that the LM317 is in dropout. That would typically be because the path from ADJ to ground is open. Double check with an ohmmeter that there is ~10k from ADJ to ground (after the caps are all totally discharged).

Pete
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Old 1st January 2018, 03:28 AM   #8
PRR is online now PRR  United States
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It would be nice to know the voltage at the Vadj pin. Actually the difference Out to Vadj. Is it 1.25V, more, less?

Agree that a "10K" not really connected would do this. Or a 100K where should be 10K (how would I know that??). But various shorts (solder bridges) might do it also.

BTW, I *think* the Gate leg "should" come on the Source side. That's how I usually see MOSFETs, and it makes sense this is a Source follower. And the wrong voltages do not look like a flopped MOSFET (I could be wrong).

Data presented so far, on diagram:

EDIT : illustration removed at request of PRR, please see post #10

Last edited by 6L6; 1st January 2018 at 09:52 PM.
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Old 1st January 2018, 03:32 AM   #9
crazyfrog is offline crazyfrog  Canada
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Help for PMillett HV regulator
I hope you guys have a lot of fun on New Years Eve! Thanks for your help. Just took a reading and found 10.6V on D1 (1N5245)...

Thanks PRR! We were writing at the same time I guess. I think your diagram will be very helpful.

Quote:
Originally Posted by PRR View Post
It would be nice to know the voltage at the Vadj pin.
The in-adj = 2.85V unless this is not you want to know.

Quote:
Actually the difference Out to Vadj. Is it 1.25V, more, less?
Right on 1.25V

Quote:
BTW, I *think* the Gate leg "should" come on the Source side. That's how I usually see MOSFETs, and it makes sense this is a Source follower. And the wrong voltages do not look like a flopped MOSFET (I could be wrong).
Actually the input goes to drain on the board.

The voltages you indicated with a ? are correct (just have 131.4V instead of 131.7V)
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Old 1st January 2018, 09:40 PM   #10
PRR is online now PRR  United States
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Help for PMillett HV regulator-pmillett-hv-130v-gif
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File Type: gif pmillett-HV-130V-b.gif (18.9 KB, 163 views)

Last edited by 6L6; 1st January 2018 at 09:52 PM.
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