yes, the output has 470K resistor to ground. I will replace MKP caps and see. These Mcap SIO are only a few months old and they are located far from the tubes.
What output tubes are there? Could it be possible that the grid resistance is too high for the grid current of the tubes you use? During the working time the current could raise the voltage on the grid and the voltage potential of one side of the capacitor. After the shut-down the potential discharges producing the pop. When you momentarily shunt the resistor you null the voltage and then the pop is gone.
The output of the preamp is 12AX7 cathode follower. But the preamp is not shut down yet . Pop happens when shutting down the solid state power amp.
Sorry, thought of tube power amplifier. It may be conditions when there is DC on the input even in solid state design.
Last night I started to manipulate the earth connection of power cord at both power amp and preamp. Finally I significantly reduced the pop by connecting the power cord of the preamp to an AC line filter that is also properly earthed.
Hi Salas,
Can I use 1N4742 (12V 1W) for D1,D2 & D3 zener diode instead of 1/2W ?
thanks,
Roland
Can I use 1N4742 (12V 1W) for D1,D2 & D3 zener diode instead of 1/2W ?
thanks,
Roland
Hi LuvValve, would you mind to summarize the mods made on the board to be able to reach 420VDC ?
That would be a great help.
Laurent
If you look back at post #4900 for what Salas wrote:
I just did according to Salas advice, cheers
Easyer than I thought
Thanks, I just thought you may have needed to change some semicond for higher service voltage ones.
Thanks, I just thought you may have needed to change some semicond for higher service voltage ones.
Hi Salas,
My ordered SSHV2 package have 2 red LEDs. Should use both LEDs at the board? or only one is enough?
BTW, can I use 0.47uf/400v at C1 which is recommended 0.33uf/400v?
Thanks
Gary
My ordered SSHV2 package have 2 red LEDs. Should use both LEDs at the board? or only one is enough?
BTW, can I use 0.47uf/400v at C1 which is recommended 0.33uf/400v?
Thanks
Gary
I don't know full details about packages, probably a spare. The circuit surely needs only one. Marked as LED1. You can use 0.47uF/400V its still within safe phase margin range.
Hi Salas,
My shunt reg is again working.
But, I used variac to slowly increase the voltage VLoad to 350Vdc.
I want to remove the variac now and connect it to Impasse.
Last time I did this - at power ON, Q1 popped and SSHV failed
Vin (unreg) is 380Vdc, is this too much to cause SSHV to fail, I don't think so?
If I remove the variac at switch ON, I'm afraid I may get the same problem
Do I need soft start circuit between Vin unreg and SSHV or any low value high power resistor in between? The reason I get rid of dropping resistor in the first place is to get rid of unwanted heat.
Can power ON at 380Vdc cause severe start up loading?
Can capacitor charging at Vunreg cause reg to fail therefore should I decrease capacitor value?
Please help.
regards,
Roland
My shunt reg is again working.
But, I used variac to slowly increase the voltage VLoad to 350Vdc.
I want to remove the variac now and connect it to Impasse.
Last time I did this - at power ON, Q1 popped and SSHV failed
Vin (unreg) is 380Vdc, is this too much to cause SSHV to fail, I don't think so?
If I remove the variac at switch ON, I'm afraid I may get the same problem
Do I need soft start circuit between Vin unreg and SSHV or any low value high power resistor in between? The reason I get rid of dropping resistor in the first place is to get rid of unwanted heat.
Can power ON at 380Vdc cause severe start up loading?
Can capacitor charging at Vunreg cause reg to fail therefore should I decrease capacitor value?
Please help.
regards,
Roland
You could increase the gate resistors of Q1 & Q2 from 100 Ohm to 1kOhm if it is a transient that troubled it into momentary oscillation, also a small value decoupling capacitor right across the input connector and possibly a circa 400V DC rated MOV (metal oxide varistor) in parallel also that would clamp an incoming transient overvoltage
Is it like this?
http://www.diyaudio.com/forums/atta...-simplistic-mosfet-hv-shunt-regs-hvshunt2.gif
Then it's not a surprise, and gate resistor doesn't help.
Rapid growing of input voltage (dVin/dt) causes overcurrent inside the badly designed shunt regulator, so you can lower the stress by increasing input cap, not by decreasing. Or by using voltage multiplier rectifier. This way you can limit inrush current without significant loss.
But if you really want to decrease power loss I recommend you to completely redesign it. With a topology like JLH amps very good results can be achieved at much lower power loss.
Last edited:
Something wrong here...
The design has already had a current "limiter" - it's the CCS between the shunt. The CCS is included in both versions of the SSHV. Where do you think there can be any "overcurrent"?
I think we are discussing power supplies here. I do not know any "new" technology invented by JLH.
"Between the shunt" has no meaning for me, since "between" needs 2 objects.
Do you mean the Mosfet rated to Vds=200V, while input voltage can exceed 300 V?
A stabilizer is an amplifier with DC input voltage. Nothing new.
Do you mean the Mosfet rated to Vds=200V, while input voltage can exceed 300 V?
A stabilizer is an amplifier with DC input voltage. Nothing new.
Sorry, English is not my mother tongue. It should read:
"it's the CCS before the shunt"
I believe Roland uses the SSHV2 (which in turn uses 400V DFET), then you link to schematic is obsolete.
Discussing the initial schematic - it is the difference between the input voltage and the output voltage that matters here. The difference is much less than 200V in the case. The start-up processes may go wrong, but in that case the possibility of the problems is rather low.
I don't know why you wrote it.