david ellwood
Kirabosi Kognoscente
Next step is to check voltages across the board
Where in the country are you? There may be a capable fishie local to you!
This may be normal but the pcb to the rear of the DAC chip is darkened. A hot IC can dry out the joints around it so they are worth checking and re-soldering if they don't look clear and shiny. I would suggest checking that each Integrated Circuit is getting power. That'll mean googling for each of the data sheets and then very carefully measuring the voltage on the power pin(s) with respect to earth while the unit is powered up. Also see if anything is getting particularly hot when powered up. Further checks beyond that are going to need a scope. BTW there's a lot of solder flux on the clock board that needs to be removed with a good scrub with some alcohol.
John
As has been said above a DVM to check the supply voltages to the chips would be a good place to start. I'm not familiar with the unit, but the fact that the optical out is working suggests the SAA7220 (adjacent to the TDA 1541A) is working which points to the TDA or the output stage which appears to be the cluster of transistor adjacent to the TDA.
Thank you.
I shall start my investigation there.
As a matter of more general interest, are TDA1541A chips available from any reliable source?
There are two opamps in the analogue circuit. I have replaced both, now mounted on sockets soldered to the board. Both are now LME49720. One was previously an LF353N, the other an NE5532N.
Both have +/-V input and are giving output voltages.