Simplistic MosFET HV Shunt Regs

[Salas]

Is this true?
4-65a SE Amp: Shunt regulator | Bartola Valves

What part? To place the Zobel cap right or not to exceed the top Mosfet's spec? Both should be watched. Crt could had marked it better I am not sure, but here is an "X-RAY" of the C1 area.

 

[JBLman]

Ok thanks!

 

[mogliaa]

What part? To place the Zobel cap right or not to exceed the top Mosfet's spec? Both should be watched. Crt could had marked it better I am not sure, but here is an "X-RAY" of the C1 area.

I failed both! it wasn't clear to me the PCB marking, but not blaming anyone as it seems I was the only one who did this
Ale

 

[JBLman]

Yea, I don't know it only puts out 58vdc and can't adjust it.

 

[Salas]

I failed both! it wasn't clear to me the PCB marking, but not blaming anyone as it seems I was the only one who did this
Ale

I will ask Crt to mark it more intuitively for the future when I will catch up with him and he has some time. Interestingly nobody reported so for missing the C1 placing, but its mainly because they use longer capacitors is my guess. Thanks for the feedback, very nice website you got BTW.

 

[Salas]

Yea, I don't know it only puts out 58vdc and can't adjust it.

All semis show proper VGS, VBE, warm up, etc.?

 

[mogliaa]

I will ask Crt to mark it more intuitively for the future when I will catch up with him and he has some time. Interestingly nobody reported so for missing the C1 placing, but its mainly because they use longer capacitors is my guess. Thanks for the feedback, very nice website you got BTW.

Thanks for the feedback. My intuition led me to place it centred given the multiple holes.
Cheers,
Ale

 

[lucek12]

Hi Salas,
I would like to buy the pcb or the whole kit- pcb+parts. Would it be possible?

 

[eboz]

SSHV2 temp drift

I recently purchased and assembled a kit from Tea-Bag. Is there any likely suspects when the sshv2 is slowly decreasing in voltage as it warms up? My heatsink is more than adequate, and I have another sshv2 that has been stable in operation for over 6mos. It seems to be temp dependent, since I can blow around the board and get the voltage to drop or stop dropping for a moment. I may have zapped a device on assembly?

Also, after it has been dropped in voltage a lot (say 5 or 10 minutes), it will begin to swing more wildly. I can compensate for the drop by turning the voltage adjustment trimmer.

 

[Salas]

Its normal to drift with temp due to the semis tempco in the Vref but not wildly. 2-3V. Leave it warm up for 15mins and then set for Vo. If it continues drifting in the tens of Volt then something's not right.

 

[eboz]

Its normal to drift with temp due to the semis tempco in the Vref but not wildly. 2-3V. Leave it warm up for 15mins and then set for Vo. If it continues drifting in the tens of Volt then something's not right.

Yes.. something is not right, because it eventually drifts down -30 or more. Any advice on what to replace first?

 

[Salas]

The JFET, then the LED if it continues so.

 

[Salas]

P.S. Oscillation can do weird things like that also.

 

[Salas]

Does it behave the same both on the dummy load and on your electronics load?

 

[eboz]

Does it behave the same both on the dummy load and on your electronics load?

Yes it does drop as it warms on the dummy load as well.i thought it might be the sensing since it was shorted on the dummy, so I wired it up for the real load which has twisted pairs for output leads. But they still had the same behavior, unfortunately.

 

[Salas]

So its not some bad interaction with the load. Proceed with the parts exchanging. Is the set current stable? What is the Vout you set for?

 

[eboz]

So its not some bad interaction with the load. Proceed with the parts exchanging. Is the set current stable? What is the Vout you set for?

Current appears stable at 35mv. Input voltage is 340 and output should be about 305. 22ma excess current.

 

[Salas]

Try raise the current first in little steps. Maybe the excess is not enough and drags down the Vo setting. Just to exclude that possibility before changing parts anyway.

 

[eboz]

Try raise the current first in little steps. Maybe the excess is not enough and drags down the Vo setting. Just to exclude that possibility before changing parts anyway.

Thanks.I'll give that a shot later tonight.

 

[AndrewT]

I would suggest you "test" the the CCS for reasonably constant current from cold to warmed up.

Attach a low voltage transformer as your power input. Attach a low value resistor across the output.