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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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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: So what have I got wrong this time? posted by vinnie2 on May 24, 2016 at 08:48:37:
I finally found the problems, and there were two of them. While trying to trace a signal through the amp with my scope, I did not see any amplification in the signal coming out or the second 26. Upon looking around that circuit for mistakes in wiring, etc, I noticed that the filaments for that tube were not glowing. Checking the connections to the filament transformer I found that one of the clip leads had worked lose and was not making contact. No wonder I could not hear any difference between two 26's and only one. After I go that fixed I cranked it back up and noticed the B+2 for the second 26 was quite a bit lower than the first 26. Tracing through that circuit I found that I had taken the b+2 voltage off the wrong side of the resistor reducing the b+2 on the first 26 and so was getting a much reduced b+2 that I was further reducing with the resistor for the second 26. Got that all straightened out and now everythsing seems to be working as it should. The gain is much improved and it sounds pretty good. Now I will have to go back and plus everything up to the operating points we came up with the first time around, and then maybe I can try incorporating these changes into the real amp. Thanks for all the help folks, it got me looking in the right direction.
Edits: 05/25/16 05/25/16 05/25/16
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Follow Ups
- Update - vinnie2 12:33:07 05/25/16 (3)
- RE: Update - deathtube 667 17:10:05 05/25/16 (2)
- RE: Update - vinnie2 17:54:09 05/25/16 (1)
- RE: Update - deathtube 667 03:55:30 05/26/16 (0)
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