Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: nicari on July 09, 2015, 07:31:02 AM
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Hello.
Yesterday I finished building my Crack. One of the first times I powered it up for testing the 6080 tube glowed very bright (like a light bulb) in a single spot of the filament. After some power on and off, I connected the input RCAs and the tube returned to glow normally and the amp worked as it should.
Today I installed the Speedball upgrade and when I turned it on for the first time I had the same problem until I connected the input RCAs and tried to turn it on again.
The problem is that even the tube glows normally the right channel is dead. I checked all the connections and they are ok, but not the voltages, terminals 1, 7, A6, B1 and B3 all measures about 170V instead of 90~100V. The two LEDs on one of the small Speedball boards don't emit light (already checked polarity).
Before starting to desolder: have you any idea of what could be the problem?
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Did you measure the voltages and listen to the amp before you installed the Speedball?
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Yes, I did. It sounded perfect without speedball (after the tube started to glow normally) and voltages where ok (apart from A1 that measured 74V insted of 90V, but it's not a huge difference).
UPDATE: I decided to start desoldering. Without Speedball the amp returned to work perfectly. The problem must be in the Speedball boards.
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Check the R1 values to be sure they are correct, check the 2N2907 and 2N2222 transistors to be sure they are in the correct places.
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Thanks! I had switched 237Ω with 31.6Ω resistor.
Solved the problem! Now is working!