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Old 14th May 2022, 3:08 pm   #2
Leon Crampin
Octode
 
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,654
Default Re: Nordmende Globetrotter 808 output stage problem.

Your problem is almost certainly due to poor circuit design around the bias adjustment potentiometer. When the wiper of an old pot makes intermittent contact with the track, the circuit shown will turn off the Vbe multiplier transistor and drive the output stage hard on. This results in a high current draw and no audio.

Replace the pot and preferably reconfigure a replacement to be between the base and emitter of the Vbe multiplier. If wired as a rheostat, connect the wiper to one end of the track. Cermet pots are best. A reconfigured circuit will need the resistance values changing.

Leon.
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