Simplistic MosFET HV Shunt Regs

[coolhead]

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

I notice you didn't use a small heat sink on Q4 & 5, is it ok?

 

[vgeorge]

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

Did you test it? What Vin Vout and current did you use?
Regarding sinking Q4 and Q5, it is necessary above 300v or so.

 

[merlin el mago]

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?

 

[merlin el mago]

My PSU it's CL only have one cap 220uF 450V & one choke 10H.

I have BG 150uF 350V & Nichicon KX 220uF 450V to put near the input reg. it's Ok the value or I need other small value?

 

[Salas]

Its OK to put very near the reg's input.

 

[merlin el mago]

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?

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

 

[quanghao]

Sorry for my typo in fact is irfp9240...

In this schematics take out D4 and D5, other changes are needed?

http://www.diyaudio.com/forums/powe...stic-mosfet-hv-shunt-regs-97.html#post2084348

Thanks.

Alberto.

i think no need!

 

[Salas]

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

Is your dummy light enough not to ask more than 40mA at 240V?

 

[vgeorge]

What dummy load did you use?
Does voltage go up when you reduce the current?

 

[merlin el mago]

Is your dummy light enough not to ask more than 40mA at 240V?

What dummy load did you use?
Does voltage go up when you reduce the current?

With the other SSHV reg I used 240V 60mA & the Puresound was sounding OK

I didn't used dummy load I use the MM as the real load.

Yes when I reduce the current the voltage goes up.

 

[merlin el mago]

It's OK if I have continuity between IRF840 & heatsink? I use two mica pads & a nylon nut & screw what is no way to isolate?

 

[Salas]

Its not OK to have continuity between 840's metal tab and sink.

 

[vgeorge]

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.

 

[merlin el mago]

Its not OK to have continuity between 840's metal tab and sink.

Isolated

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.

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?

 

[Salas]

Use 10k to be light and try turning the trimmers. Led should be on.

 

[vgeorge]

Voltage between gate and source should be 3,5V to 5V.
Check also that you do not have long leads between last cap and reg.

 

[merlin el mago]

With 10K dummy load (two 4k75 in series) fixed 17 Vout can go up or low using R11 1K trimmer

 

[merlin el mago]

Voltage between gate and source should be 3,5V to 5V.
Check also that you do not have long leads between last cap and reg.

VGS 3.9V
4-5cm

 

[vgeorge]

Then the 840 is OK.
Check the BE voltage of the SA1381. Should be around 0,6V.
Led is lit?

 

[merlin el mago]

0,15V
Yes