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14th January 2012, 07:12 PM  #2551 
diyAudio Chief Moderator

We have one running at 60mA among the proto testers (with no problems), and I will ask at what value the trimmer and resistor combination measures. Its an area I am expecting some practical feedback due to possible differences to datasheet and IDSS spread of the Supertex. In the end we will designate the most ''safe'' values. But I would like to see a fixed resistor replacing the CCS trimmer in permanent installations after initial fixing. Its good for PPM & long term ease of mind.

14th January 2012, 08:01 PM  #2552 
diyAudio Chief Moderator


15th January 2012, 03:31 AM  #2553  
diyAudio Member
Join Date: Mar 2009

Quote:
Edit: bugger me ! I can calculate Vgs by myself :P 1.21V . But I'm still interested to know Vds of Q2. Last edited by Lazybutt; 15th January 2012 at 03:44 AM. 

15th January 2012, 03:44 AM  #2554 
diyAudio Chief Moderator

Can you calculate Q1 Vgs?

15th January 2012, 03:56 AM  #2555 
diyAudio Member
Join Date: Mar 2009

A little bit difficult because Q2 Vds enters into play, so it starts to be tough in Excel. I'll give it a try...
My Calc just neglects Q1 altogether. I suspect the difference between my value and the real life may come from this calculation approximation ( although my gut feeling would have been that R4 would be lower than what I calculate.. not higher.... ) 
16th January 2012, 12:51 AM  #2556  
diyAudio Member
Join Date: Jul 2009

Need help on SSRHV1
Quote:
I've reduced R1 to 14ohm and mount the Q1 & Q3 on larger heatsink add heatsink to Q2. I connected a 5.6K 20W as dummy load and test the regulator. With input 300V, I adjust the VR to have 250V output but it drift up slowly to the same value of the input. Please advise the possible problem. 

16th January 2012, 01:27 AM  #2557 
diyAudio Chief Moderator

Possibilities: 2SK147? Very drifty especially if heated up enough. Try BF245A. Cable connections to the Mosfets? Possible oscillation. Bad trimmer? Can drift. Did you check there is VGS voltage on Mosfets and Vbe voltage on the transistor? All semiconductor parts should be checking OK first.

16th January 2012, 06:07 AM  #2558 
diyAudio Member
Join Date: Jul 2009

Checked the voltage at R1 drift from 1.54 down to 1.4x. Vgd a Q1 is 4.066, Q3 is 2.958. I believe is the 2sk147 problem. Can I use J201 to replace it?

16th January 2012, 10:18 AM  #2559 
diyAudio Chief Moderator

J201 will have low IDSS, maybe less than 1mA sometimes so you will need double the R4 value plus maybe. Its also noisier. Use it if having nothing else. For drift is stable enough.

16th January 2012, 01:28 PM  #2560 
diyAudio Member

Felipe,
got my caps too. Thanks a lot. 
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