Hi apologies if this is in the wrong forum, but i have just acquired a near mint technics sa515 integrated tuner amp. However the protection led is lit and there is no sound. I have checked the voltages on the SVITA 7317P speaker protection ic and on pin 6 i am getting 47 volts DC whereas the service manual says 1.3 v DC.
I replaced the D617 diode close to this pin 6 as it had battery acid leaked from the FM memory channel storage but still getting the 47v .
The protection Relay coil also connects across this pin 6 and the 47 v dc but not sure from the circuit diag what its supposed to do as its the coil connected across it.
Cheers
For any advice
I replaced the D617 diode close to this pin 6 as it had battery acid leaked from the FM memory channel storage but still getting the 47v .
The protection Relay coil also connects across this pin 6 and the 47 v dc but not sure from the circuit diag what its supposed to do as its the coil connected across it.
Cheers
For any advice
Sounds like you have DC on the speaker terminals to the protection relay.
Check TP603 & 604 for zero volts with respect to 0volts
Check TP603 & 604 for zero volts with respect to 0volts
Not looking good, suggests blown/short output transistors and open emitter resistors in the IC. You should carefully measure voltages on the other pins to rule out BS in, BS out. Avoid measuring at actual pins, use connect parts eg, D606 for pins 12&13
Thanks will check the volts on connecting parts tomorrow, like you say looks like a blown STK ic. It's a pity as it's in good condition ..
STK8050 were a temperamental ic that seems to get brittle over time... seen a few pack it in for no reason
Have seen periodically STK8070 ics that should fare better
Have seen periodically STK8070 ics that should fare better