Further to the above....when i search "All Transistors. 37740 Datasheet" it states MIN hfe should be 140 which puts both of mine out of spec.

Next up right channel power output transistors.....green text

left channel power output transistors.....green text

Left stage is just about in spec, should be hfe 20-70 I believe....measured these by disconnecting from the circuit board as I thought it looked easier than disconnecting at the transistor base...….left stage low

Second left stage also low......

right stage looking better...….

Second of the right also looking good......

So....I have ordered a bunch of BC550B and BC560B to replace the black tops....I have also 2N5320 and 2N5322, this said I feel I should also change the left stage 2N3055 devices, Martin I'm looking at you 😁 could you let me have a couple from your bottom draw?

Craig

Craig wrote:

So....I have ordered a bunch of BC550B and BC560B to replace the black tops....I have also 2N5320 and 2N5322, this said I feel I should also change the left stage 2N3055 devices, Martin I'm looking at you 😁 could you let me have a couple from your bottom draw?

Craig

Sure you can Craig, - but why do you question the original ones?

Martin

Craig,

If I were you, I would just change the IC 423 for now.  When everything is in order, check the output level difference between both channels and see if this is manageable with the input potentiometers. Now, I can't see the output transistors.  Are they all original?  Were they replaced on the left channel?