Simplistic Mosfet HV Shunt Regs - Page 358 - diyAudio
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Old 13th December 2012, 10:44 PM   #3571
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Salas I used this PSU and R5 SSHV2 burned: fire

Can be to high Vin voltage: 346VDC, when Vout target is 280VDC after SSHV2?
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Old 14th December 2012, 01:15 AM   #3572
Salas is offline Salas  Greece
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R5 (10 OHM TP resistor) catching fire means strong current. Because its the passing bridge from CCS part to shunt part. I don't see more than 2W on CCS Q1 sink if drawing 30mA over a 66V drop, so it should have been something in the grounding or handling that took out one or two CCS semis. (How did you try ground the voltage doubler? Diodes must be 2xPIV. Transformer can supply half its normal current). We rather recently discussed using 100mA 500V ceramic fuse in series to SSHV2 when you experiment...
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Old 14th December 2012, 01:22 AM   #3573
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Quote:
Originally Posted by king4joy View Post
Salas....I changed the shape of the heat sink and now I am fitting two SSHV2 boards in my PSU box....

I will set each board to about 30mA giving about 8-9mA to each VT25A tube.

If I connect 2 x SSHV2 boards to the PSU instead of one SSHV2, do I need to change the bleeder value or other parts of the PSU??
It will have impact only on series drop resistors or coils internal resistance. If you had calculated Vo for strong bleeders, recalculate DCin including two CCS and bleeders total for drop on series elements mentioned.
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Old 14th December 2012, 12:48 PM   #3574
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Quote:
Originally Posted by Salas View Post
R5 (10 OHM TP resistor) catching fire means strong current. Because its the passing bridge from CCS part to shunt part. I don't see more than 2W on CCS Q1 sink if drawing 30mA over a 66V drop, so it should have been something in the grounding or handling that took out one or two CCS semis. (How did you try ground the voltage doubler? Diodes must be 2xPIV. Transformer can supply half its normal current). We rather recently discussed using 100mA 500V ceramic fuse in series to SSHV2 when you experiment...
I explaint you:

-I tried the voltage doubler because I have a Bartolucci 125VAC 100W that I don't use, your 6V6 tube lineamp uses 340VDC, others lineamp I'm experimentig uses 250VAC, 280VAC & 300VAC that's the reason I tried.

-I used the voltage doubler without the chokes: R/C/R/C 600R/40uF/600R/40uF with the Bartolucci tx and worked OK.

-Before to connect the new R/C/L/C/L/C I verified with a dummy load 15K to adjust the voltage & current working fine without burning nothing, only burned with the real load.

-I tested the wires between the reg & the real load & all wires are OK.

-Sorry my ignorance, what's 2xPIV? something relationated with power & voltage?

-Yes you told me the ceramic fuse but can't get in the local shop, I wil include in the next online order to RS or Farnell.

Last edited by merlin el mago; 14th December 2012 at 12:55 PM.
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Old 14th December 2012, 12:50 PM   #3575
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peak inverse voltage !
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regards Andrew T.
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Old 14th December 2012, 01:19 PM   #3576
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On having dismantled the regulator I have realized that the screw that holds Q3 was sluggish(weak), can it be the reason of that is situated burnt R5?
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Old 14th December 2012, 01:40 PM   #3577
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Quote:
Originally Posted by AndrewT View Post
peak inverse voltage !
Thanks
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Old 14th December 2012, 01:43 PM   #3578
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UF4007 PIV 1000V, I have to use 2000V?
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Old 14th December 2012, 02:29 PM   #3579
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Quote:
Originally Posted by merlin el mago View Post
I explaint you:

-I tried the voltage doubler because I have a Bartolucci 125VAC 100W that I don't use, your 6V6 tube lineamp uses 340VDC, others lineamp I'm experimentig uses 250VAC, 280VAC & 300VAC that's the reason I tried.

-I used the voltage doubler without the chokes: R/C/R/C 600R/40uF/600R/40uF with the Bartolucci tx and worked OK.

-Before to connect the new R/C/L/C/L/C I verified with a dummy load 15K to adjust the voltage & current working fine without burning nothing, only burned with the real load.

-I tested the wires between the reg & the real load & all wires are OK.

-Sorry my ignorance, what's 2xPIV? something relationated with power & voltage?

-Yes you told me the ceramic fuse but can't get in the local shop, I wil include in the next online order to RS or Farnell.
You can use 300V and 7.5K instead of 5K plate resistor and 340V in my 6V6 pre.
Is the real load referencing to ground, and where is the doubler being grounded? What happens if you don't ground the chain from doubler to reg to 6V6?
You can use two diodes in series where there is one shown, that doubles the peak inverse voltage spec.
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Old 14th December 2012, 02:56 PM   #3580
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Voltage doubler is not connect to chassis gnd, not connect to AC mains earth. Have I to connect to mains earth or to chassis gnd?

Yes, real load is grounded to chassis gnd, also SSHV2 is grounded to chassis gnd.

Thinking about the changes that I have introduced, now I use 2 chassis instead of only one and between both chassis there is no connection of AC earth, can be the issue?

Last edited by merlin el mago; 14th December 2012 at 03:04 PM.
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