Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: mishak on March 10, 2020, 01:25:58 PM
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Hello all. Just want to say I've loved my BHC the past year, and this amp is pretty wicked!
I purchased it with the SB 1.1 upgrade, and as advised, I used BHC without speed ball for about a year. I added the small PCB this weekend and used the amp without any issues after "stage 1" of the SB upgrade. Today I decided to add the larger PCB part of the upgrade and initially the two LEDs on the OB side of the PCB weren't lit up. The voltages were off, and I re-soldered some joints and then they lit up just fine. When checking voltages, OA is reading around 115 and OB around 110. I tried reheating the TIP-50 legs again and added a bit more solder, however the voltages are reading the same. The amp is working fine currently, but I just want to make sure its OK. Thank you all in advance.
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What are the OA and OB voltages on the small board? I would suspect that they are a little on the high side, and that may be moving the voltages at the outputs of the big board up a little as well.
It's also worth mentioning that a really, really strong 6080 will show a greater difference in voltage between the OA/OB on the small board and the OA/OB on the big board.
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OA and OB on the small board at 85 and 79 respectively
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Yeah, so that's a little high. I wouldn't be concerned about what you're seeing. You have a 12AU7 that's not super fresh (but totally within normal operating specs) and a 6080 that's got strong emission. The two in concert are pushing those OA/OB voltages on the big board up a little bit.
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thank you so much for the prompt reply!