That (error) current exits the collector. The difference of Vbase and Vspeaker becomes a current across the 820 ohm between speaker and emitter. The T601 is where the input signal ( from Preamp ) is subtracted from the feedback signal to the loudspeaker. Schematic- T601 is the one that needs replacing: If not, there are some random parts I groused up on Mouser based on the filters that seem like they might be appropriate, but I'm for those I'm casting around in the dark a bit. I'm not knowledgeable enough to look at the circuit and see why the schematic shows the BC158 and the actual part used was a BC158B- they appear to be likely different in amplification function, but maybe (presumably?) it doesn't matter here.Ĭan anyone offer a theory for why the original part used could be a higher-gain model without messing anything up?ĭo I need to seek out a higher-gain replacement part? I'll use a 2N3906 if it would seem to work. It appears to me that a standard general purpose 2N3906 would seem appropriate relative to the base BC158 (has same or higher max voltage, higher max current, and similar hFE.
#2n3906 transistor substitute for 2n1307 how to
I have asked before here and gotten good advice on how to think about transistor equivalence in audio when going from vintage euro parts to current US replacements. Here's a datasheet showing the BC158 series.
The only difference between the BC158 and the B variant is the hFE gain value (higher value in the B).
(Schematic with highlight is below.) The part on the actual board is a BC158B the schematic specifies only "BC158". I have identified a failed (shorted) PNP transistor in the power amp section. On a long but educational process repairing a vintage German stereo.
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