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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: update to B+ dilemma.... posted by vinnie2 on July 21, 2014 at 15:27:05:
I was reviewing the schematic once again to see if I had missed anything and I think I did.
The situation is that I have a B+ of 272 vdc after filtering and I need 250 for the phono pre. I think I may have found an easy solution, but I am gun shy since I have missed on a couple others and am hoping you guys can tell me if I have it right this time......
On the schem for the phono stage (see link) it shows the B+ basically going to R9 and R4 which are 30k each. I looked at the RCA tube manual and it says that standard operating plate voltage is 90 vdc for the 6dj8, so I assume the designer of the circuit was shooting for something near that. I had some nice wire wound 5w 39k resistors in my bins so I stuck a couple of those in for R4 and R9. I had previously measured the voltage at the plate side of those resistors as 112 vdc (about 22 over the desired) and when I measured with the new resistors it was 93 vdc. Close enough I think.
Looking at the schem it doesn't look to me like that one change will effect any of the other down stream voltages adversely as they all were probably proportionally too high with the 270 B+. Also seems like it should be ok for the caps too, or do I have it wrong?
Edits: 07/22/14 07/22/14 07/22/14 07/22/14 07/23/14 07/23/14 07/23/14 07/25/14 07/25/14 07/25/14 07/26/14
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Follow Ups
- I may have found the solution.... - vinnie2 15:32:31 07/22/14 (1)
- No comments? - vinnie2 07:51:36 07/24/14 (0)
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