Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: spunko on March 29, 2021, 04:34:02 pm
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Hola amigos.
I got this JetCity picovalve 6L6 / 5 watts amp, which has a bad preamp socket (V2). The amp worked fine, but if the second 12Ax7 moves a bit, the sound stops and it mutes completely. Move it again and the sound comes back.
I took off that particular tube and inspected the socket. There were some terminals wide open, so I tightened the terminals using a needle and a lot of care, inserted the tube again and it was a good fit.
Then I tried the amp, power on and no glow on the tubes, hit the stand by and no sound at all.
It is weird because the amp was just fine when I tested it, I just tightened that socket terminals. I didn't even touch the PCB so I really don't know what the problem is.
I haven't found an original schematic, just one that some nice person draw, but it lacks of voltages (attm).
I checked were I think the filament voltage should be (orange wires) and both gives 7 VAC.
It also has +B, 368VDC on PIN3 - 365VDC on PIN4, and it doesn't have negative -V on PIN 5 on the power tube socket (no tubes installed).
What should I check?
(https://i.imgur.com/Ud95vrK.jpg)
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PCB so I really don't know what the problem is.
the PCB part :icon_biggrin:
spend quality time re-soldering bad solder joints
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PCB so I really don't know what the problem is.
the PCB part :icon_biggrin:
spend quality time re-soldering bad solder joints
I thought about that, because the solder work looks so bad. I have to unsolder all the wires from the transformers to take out the pcb :BangHead:
I noticed I have 7.0 VAC on the orange wires, but 0.0 VDC from diodes below them (D5,D6,D7,D8)
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PCB so I really don't know what the problem is.
the PCB part :icon_biggrin:
spend quality time re-soldering bad solder joints
It was that, resoldering some suspicious spots and the amp works great again