This amp has been the worst of all so far to find the lost channel issue - I traced the whole audio path first, checking components, damaging tracks and wasting time in a rabbit whole.
Power/voltages come before a signal! All I had to do was check the voltages on the main board ribbon connector against the schematic and I would have found 3.4V feeding all the ICs instead of the correct +7.4V from the +/- 14V regulator transistors:
This voltage feeds pins 16 of each switching IC, so after tracing from the mains rectifier +/- 37V lines to the q809 transistor (which I removed and checked, with it's diode - both OK!).
I snipped the leg of IC501 pin 16 and the power levels at the other ICs jumped up. Fault found!
Need to replace the MC14051 multiplexer. Is the pin out the same as a 4051?
"The NLAST4051 is an improved version of the MC14051"
1997 - SONY LCD TV CIRCUIT DIAGRAM FREE
Abstract: tsc8701 CXA1179 TLC320AD55 tlc5491 tlc5620 TSC8704 CMOS AREA IMAGE SENSOR 24pin TLC8044 ADC0830
Text:- TLC1541- Motorola F- LTC1294- TLC2543- Linear Technology S- MC14051- TLC1541- Motorola S- LTC1296- The device an EXACT- EQUIVALENT- in functionality and parametrics to the competitors , Vendor Vendor Replacement Type- TLC2543- Linear Technology P- MC14051- TLC1542- Linear Technology S- LTC1296- TLV2543- Linear Technology P- MC14051- TLC1542- Motorola S- LTC1400- TLC5618- Linear Technology Q- MC14051- TLC1543- Motorola S- LTC1446