Simplistic mosFET HV Shunt Regs

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#2,842
merlin el mago said:
Attached my finisfed SSHV2, heatsink IRF840 1C/W isolated from chassis with bitumen car dampers self-adhesive, heatsink DN2450 4,5C/W, for caps I used the ones I have on my stash: 10uF 400V Solen & 0,33uF 425V Infinicap Wonder Signature TRT, resistors & semis are from Mike (aka Tea-Bag) minikits🙂
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Did you test it? What Vin Vout and current did you use?
Regarding sinking Q4 and Q5, it is necessary above 300v or so.
 
#2,843
Vin 284V, my Vout target 240V, my current target 60mA but can't turning R4, the minimum current that I reach is 171mA.

I have two separate boxes(one for PSU & the other for the RIAA), I need to put one cap near the input regulator, if yes wich value?
 
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#2,846
merlin el mago said:
Vin 284V, my Vout target 240V, my current target 60mA but can't turning R4, the minimum current that I reach is 171mA.

I have two separate boxes(one for PSU & the other for the RIAA), I need to put one cap near the input regulator, if yes wich value?
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My fault I have 17mA instead 171mA😱

Now 600mV across TP but only reach 15Vout with R11.

Heatsink DN2450 is very very hot. Heatsink IRF840 is cold with 1C/W
 
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#2,854
Salas said:
Its not OK to have continuity between 840's metal tab and sink.
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Isolated


vgeorge said:
Use a dummy load around 5k, to be sure there is no other mistake and test.
Do not fire the reg until you isolate it from the sink. You have the full output voltage on the sink now, which is kind of dangerous - even lethal.
I use a sil pad and screw with washer and no problems so far.
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I use 4K75 as dummy load, Vout max 17VDC, TP 600mV = 60mA😕

I'm afraid IRF840 isn't working wich voltage have to measure VGS?
 
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