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Simplistic Mosfet HV Shunt Regs
Simplistic Mosfet HV Shunt Regs
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Old 13th May 2012, 10:13 PM   #3011
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Just buffer the 5uF on the load's rails with 1R in series. Your zobel values are not the problem. Your rails capacitor worsens the phase margin right near the point of full oscillation. Don't use inductance after the reg. Or any other networks for that matter.
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Old 14th May 2012, 05:42 AM   #3012
triode_al is offline triode_al  Netherlands
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Quote:
Originally Posted by Salas View Post
Just buffer the 5uF on the load's rails with 1R in series. Your zobel values are not the problem. Your rails capacitor worsens the phase margin right near the point of full oscillation. Don't use inductance after the reg. Or any other networks for that matter.
Learning a lot!.

You think the power FET would not have been zapped then?
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Old 14th May 2012, 07:24 AM   #3013
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Why? Are there any indications it got zapped? Remains cold or something?
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Old 14th May 2012, 12:12 PM   #3014
triode_al is offline triode_al  Netherlands
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Zapped?? Just afraid. But you are right, it can't be the module.

I'll rework. I have now all caps with 1-5 ohms and will insert the shunt again later on.
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Old 15th May 2012, 04:30 PM   #3015
triode_al is offline triode_al  Netherlands
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I think I found out the reason for my persistent problems, problems that got worse and worse: one of my 6SL7's heaters was breaking down. It is now dead - though I measure a resistance on the tube, as soon as I apply a current it pops open and there is no current any more

In fact not true 6SL7 but the russian 1578. I had them in series & with DC even though it was slow start.

I think: This caused the non-systematic drops in heater current and voltage sags.

I now have old ECC35 in the circuit, though a lot more noise, well sounding.

Have to revisit the heaters first of all though .... think I will go current source. Then restudy the Salas SSHV1
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Old 15th May 2012, 06:02 PM   #3016
triode_al is offline triode_al  Netherlands
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correction: In fact not true 6SL7 but the russian 6N9S
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Old 15th May 2012, 06:35 PM   #3017
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
OK, let us know your progress & good luck.
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Old 20th May 2012, 11:52 AM   #3018
Brouilly is offline Brouilly  United Kingdom
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I am putting together a 26 preamp with transformers I have on hand, and I need to drop about 40V. Should I drop before the SSHV reg or use the reg to drop that much? Will it make the board too hot? Will a higher output impedance affect the performance of the reg?

Will order a better rated transformer but it would be nice to use what I have on hand for now.

Thanks

Charlie
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Last edited by Brouilly; 20th May 2012 at 11:59 AM.
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Old 20th May 2012, 12:03 PM   #3019
vgeorge is offline vgeorge  Greece
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Simplistic Mosfet HV Shunt Regs
Charlie,

if you have enough heatsinking for the 840 it will be fine.
The board doesn' t get hot.
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Old 20th May 2012, 12:18 PM   #3020
Brouilly is offline Brouilly  United Kingdom
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Thanks, heat sink is excessively large so i'll drop it in the reg. Looking forward to hearing the results!

Cheers

Charlie
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