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Help for PMillett HV regulator
Help for PMillett HV regulator
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Old 1st January 2018, 10:21 PM   #11
6L6 is offline 6L6  United States
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Help for PMillett HV regulator
Do you have RV1 removed and open or jumpered? It needs to have a jumper so R4 can connect to ground.
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Old 2nd January 2018, 04:45 AM   #12
crazyfrog is offline crazyfrog  Canada
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Help for PMillett HV regulator
RV1 (2K) is well installed but set at "zero" just to make the test simpler. In that case the reading between LM317 adj pin and ground is 10K (R4 value).
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Old 2nd January 2018, 04:53 AM   #13
crazyfrog is offline crazyfrog  Canada
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Help for PMillett HV regulator
Quote:
Originally Posted by PRR View Post
Click the image to open in full size.
Thanks again. But there is still a GD thing I don't see on that board...
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Old 2nd January 2018, 09:50 AM   #14
FLT is offline FLT
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Default stupid question...

Hi,

you have 140V Input and 130V Output= 10V Difference.
D1 is a 15V Zener and R1 has 100kOhm.
For a Zener current of 1mA R1 has 100V drop.

I don't know how this can work and didn't find an Input voltage range
on pmillet's site.

regards

frank
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Old 2nd January 2018, 01:50 PM   #15
6L6 is offline 6L6  United States
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Help for PMillett HV regulator
I'm wondering about dropout as well. But remember he wants 105V output.

Crazyfrog - solder a 7-8k resistor (or so) across R5 and then see if you can get any adjustment in output voltage with the pot.

The other trick to try is to make R5 100ohm or so, which will pull more current through the 317
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Old 2nd January 2018, 05:17 PM   #16
crazyfrog is offline crazyfrog  Canada
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Help for PMillett HV regulator
Default Found it!

Re-checked all ( possible) parts with DMM: GOOD
Re-checked for discontinuity from part to part: GOOD
However, since 10.6V on D1 was "weak" (see post 9), I took readings of voltage backwards from there until the adjust pin: BAD from D1 to R3. The bobo was 1N4148. And it was testing good... Never occured to me to check there. Anyway I just put a new one and it's working fine. Thanks to all for your help and interest (especially to PRR for the "educational" diagram ).
Pierre
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Old 2nd January 2018, 05:48 PM   #17
AndrewT is offline AndrewT  Scotland
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Are D1 & D2 referenced to the output voltage?

What happens at start up when the output voltage is at zero volts?
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Old 2nd January 2018, 06:32 PM   #18
PRR is offline PRR  United States
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Quote:
Originally Posted by AndrewT View Post
...What happens at start up when the output voltage is at zero volts?
Output at zero. D1 holds Q1 Gate at +15V. Q1 Source rises near +18V. The LM317 is entirely safe for voltage; Q1 must stand about 120V but is a 700V part (tho shunted with a 530V TVS). LM317 can still shut-down on over-current, any large output cap will charge at ~~1A. Less if it goes on long enough to make the '317 hot.

The whole D1-Q1-LM317 rig rises as output voltage rises. '317 should never have over about 18V across In/Out. If we screw-up, D5 should limit to 39V across the '317.

There are more stumbles possible when power turns off. That is why you need D5 D3- so any output cap is discharged around the '317 (which dislikes reverse current). Also D2 takes-down bypass C2.

If D2 is shorted, output setpoint is 210V. With only 140V coming in, it may go to 130V. If D2 is installed (or marked!) backward, output setpoint is 155V-160V, so again we may get 130V.
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Old 3rd January 2018, 07:57 AM   #19
AndrewT is offline AndrewT  Scotland
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Thank you for talking/taking me through that.
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