Simplistic Mosfet HV Shunt Regs - Page 337

Salas · 20th October 2012, 11:25 PM

The Zeners and/or the FET are suspicious. The FET especially goes pop without drama in over voltage. But check the CCS works after R1 change and possibly D1 or worse Q1. See at 12V as you say. It was left on how high a voltage input for 5sec?

RollE2k · 20th October 2012, 11:45 PM

230V input voltage, and it may have been 10 sec, since i had time to take the multimeter measuring. 100mA load.
Will check the zeners also. By fet you mean the IRF840?

Salas · 21st October 2012, 12:14 AM

No, the JFET. 230V to 13.5V * 0.1A hmm, it gave Q1 some stick for 10 sec. Proceed to step autopsy.

RollE2k · 21st October 2012, 12:41 AM

the Q1 sink didn't become that warm, but the R1 did burn, so it may have lived through it.
So i will try change the Q6 then, after i have checked the CCS part.
D3 seems like a candidate which may have died?

Salas · 21st October 2012, 01:14 AM

Yep.

RollE2k · 21st October 2012, 06:52 PM

Changed all diodes, since they seemed to be broken (i got contact on them both ways with multimeter), then i changed the R1 and the JFET. Tried measure all resistors on board, and it looked right. tested the CCS with 12v between +input and +f which worked fine.
plugged everything in, started with 230v filtered input, and R1 burned again. Seems like something with the shunting?

Salas · 21st October 2012, 06:59 PM

Do the replaced diodes do the same conducting when off circuit? The 840's gate oxide could be hit when sparking, you are not left with much to check. That and the two BJTs.

roger57 · 21st October 2012, 07:06 PM

Sorry if this question has already been posted; did some searching but could not find. Please reply with posts if already answered or threaded.

Has anyone set up an SSHV2 with about 450V input (about 30mA at load required), and what components were changed (need to be changed) ?

Thanks,
Gary

Salas · 21st October 2012, 07:14 PM

If the Jfet has enough Idss you can got about 400V out without changing anything, about input over 400V me no, because the CCS Mosfets are 400V rated, though that condition is over run only just before the output develops, but at your risk.

Salas · 21st October 2012, 07:15 PM

RollE2K, does your DMM light up LEDS in diode mode? Has 2-2.5V? See that the LED can still light up to be sure before proceeding.

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20th October 2012, 11:25 PM	#3361
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	The Zeners and/or the FET are suspicious. The FET especially goes pop without drama in over voltage. But check the CCS works after R1 change and possibly D1 or worse Q1. See at 12V as you say. It was left on how high a voltage input for 5sec?

20th October 2012, 11:45 PM	#3362
RollE2k diyAudio Member Join Date: Nov 2007	230V input voltage, and it may have been 10 sec, since i had time to take the multimeter measuring. 100mA load. Will check the zeners also. By fet you mean the IRF840?

21st October 2012, 12:14 AM	#3363
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	No, the JFET. 230V to 13.5V * 0.1A hmm, it gave Q1 some stick for 10 sec. Proceed to step autopsy.

21st October 2012, 12:41 AM	#3364
RollE2k diyAudio Member Join Date: Nov 2007	the Q1 sink didn't become that warm, but the R1 did burn, so it may have lived through it. So i will try change the Q6 then, after i have checked the CCS part. D3 seems like a candidate which may have died?

21st October 2012, 01:14 AM	#3365
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Yep.

21st October 2012, 06:52 PM	#3366
RollE2k diyAudio Member Join Date: Nov 2007	Changed all diodes, since they seemed to be broken (i got contact on them both ways with multimeter), then i changed the R1 and the JFET. Tried measure all resistors on board, and it looked right. tested the CCS with 12v between +input and +f which worked fine. plugged everything in, started with 230v filtered input, and R1 burned again. Seems like something with the shunting?

21st October 2012, 06:59 PM	#3367
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Do the replaced diodes do the same conducting when off circuit? The 840's gate oxide could be hit when sparking, you are not left with much to check. That and the two BJTs.

21st October 2012, 07:06 PM	#3368
roger57 diyAudio Member Join Date: Sep 2006 Location: Edmonton, Alberta	Sorry if this question has already been posted; did some searching but could not find. Please reply with posts if already answered or threaded. Has anyone set up an SSHV2 with about 450V input (about 30mA at load required), and what components were changed (need to be changed) ? Thanks, Gary

21st October 2012, 07:14 PM	#3369
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	If the Jfet has enough Idss you can got about 400V out without changing anything, about input over 400V me no, because the CCS Mosfets are 400V rated, though that condition is over run only just before the output develops, but at your risk.

21st October 2012, 07:15 PM	#3370
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	RollE2K, does your DMM light up LEDS in diode mode? Has 2-2.5V? See that the LED can still light up to be sure before proceeding.