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Post by paulyd on Jun 18, 2019 7:51:15 GMT -7
Hi I wonder if someone can help. My Dr Z Maz has gone down for the second time in a few months. It works for about 30 minutes and the just fizz's out, 2 of the power tubes at the back are glowing redhot . Ive had it repaired once in the last few months and had the tubes replaced but the same problem keeps happening and id rather not take it back to the place that fixed it last time as I now don't trust them.
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Post by zpilot on Jun 18, 2019 8:27:49 GMT -7
I would start with checking the bias resistor for those tubes. Then any other components and connections common to those two tubes.
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Post by paulyd on Jun 18, 2019 9:25:28 GMT -7
Hi, thanks for your reply. where would I find the bias resistor?
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Post by Jaguarguy (Mike) on Jun 18, 2019 9:57:36 GMT -7
You might want to send the chassis back to Doc for a once over. Definitely worth the price!
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Post by paulyd on Jun 18, 2019 11:10:58 GMT -7
Thanks for the suggestion, unfortunately I live in the UK.
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Post by DRZ on Jun 18, 2019 12:41:00 GMT -7
Look at the Grid resistors ( 1.5K ) which are mounted on each output tube socket. Pay close attention to the two tubes that are glowing , and look to the jumper wire that connects the two grids. I would just re solder those connections first , melt some solder on the pins. Then change the two tubes that glowed. They probably are still good , but once they runaway they can't be trusted, so replace them.
Z
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Post by paulyd on Jun 18, 2019 13:07:05 GMT -7
Thanks doc, I’d rather get it into a repair shop. Is there one you recommend?
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Post by DRZ on Jun 18, 2019 13:24:29 GMT -7
Who ever John Peach ( Peach Guitars ) uses is very good.
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Post by paulyd on Jun 18, 2019 14:16:00 GMT -7
Thanks Doc, I’ll call them.
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