Clueless Idiots and High Voltage Vacuum Tubes Really Do Mix!

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I Not Dead Still

October 7th, 2012 · No Comments · Amp Repair, Debug

So again.. not dead. Opened an amp for the first time in a long time today. Crestline 5T. This is the one I’ve been threatening to mod heavily. I decided today to just get her checked out for the fun of it. When last I saw her, she had burned a fuse holder (don’t ask me how, I guess a short). So I put the new one in and had to go digging around to find the tubes for her.

She started fine and had excellent voltage readings everywhere, but she wouldn’t make a sound. For quite some time I farted all over the output circuit, finally coming to the conclusion that my multimeter was faulty. Switched to the new one and saw signal passing around (finally) and realized that there must be something wrong with the speaker connection.

Sure enough … the phono jack connector broke on the inside, so I was doing all of that testing on an unloaded transformer (and up to 11 a fair bit of that time.) Once I got sound, I got what I expected (ish) from the high registers, but any thing lower than F3 (3rd ‘D’ string 3rd fret) would just fart horribly.. It sounds very much like 2nd harmonic distortion (terrible buzz) and I’m guessing I’ve either blown a speaker or the OT (I predict the tranny).

I’ll have to try a new speaker and if that fails me, I’ll have to dust off the ‘scope. If that happens I suppose I could post step by step descriptions. Breathe a little life into this poor blog.


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