Simplistic MosFET HV Shunt Regs

diyAudio Chief Moderator
Joined 2002
Paid Member
Hi Salas, wishes of happy new year.

I need your help if possible, yesterday working late and tired, I did a stupid mistake with one working SSHV2 board, I connected my meter probes set to measure on the 20A range, to the output of the board, wanting to measure voltage :mad:

Of course this produced a nice small flash on the terminals/probes, and the regulator stopped working. The led is still on, but now I get only around 6,4V on the output.

What I need is for you to tell me in your opinion what should be changed to avoid taking all transistors out.
Many thanks.

Check Vgs and Vbe on all semis to pinpoint broken ones.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
P.S. I see MJE350s? Those are not usually fully in plastic and your silver mini sinks look touching. That would mean a short between collectors.
 

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Salas,

I still owe you a picture of AZ1 with black meshies...

Shunt works fine now after replacing the semis altogether, very good sound with D3a phono/silk stepups, I raped PCB from Quanghao, and built it with different circuit.
Unfortunately my digicam broke, so no pics of the internals of the actual phono stage, only unfinished with SSHV1.
Enclosures are from fleamarket (5€), little spray, mdf, veneer, some evenings spare time.

Sure enough I am going to put those regs everywhere possible, big upgrade everytime I use them.
BTW I bought a Peakatlas transistor tester, very useful to sort out the dead from the alive:cool: . Before I had to throw away the suspected semis , now I can check out the actual culprit and keep the healthy ones.
So thanks one more time for spending all this time here to help out those helpless guys fixing their burnt regs ...


cheers,

Juergen
 

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Yes, you are right, it is a bit risky, but was the only way to squeeze the tube in. If the filament hangs a little bit too much--bang, short and over. But I bought this one for 4€ because the getter was loose, and have some more different AZ1 for spare.
I would not do this with a WE 300B ;)
 
Hi all.
So I've just put together my SSHV2 board.
My target is about 210v at 72ma (+20ma). The ccs only manages 72ma though with a real load.
My initial testing had a dummy load of 2.5k, which I now realise was wrong (the psu will drive 4 ccs loads, each of which outputs 180v, 18ma). The incorrect dummy load gave me 210v and 92ma
I also now see what a difference a few hundred ohms makes in that range.

So what are my options for getting the ccs up to level?
I've trawled through the thread, but it information is tricky to find sometimes!
 
70V drop, it is very big, only need 20V drop.

you can art the R 470 Ror 1K/5W before SSHV shunt!

It is a big drop, but 70v with 92mA is well within the limits of my heatsinks.
FWIW, I replaced R5 with a 1 ohm resistor, and he voltage is steady at 210v. The current started at 93ma, and slowly drifted to 92.5.
The next plan is to leave it running for a while, then readjust. How long will be ideal before I can deem everything stable?

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