Yamaha CA-2010 Relay issue

[TommyW]

Look at D402 and R403 100Ω 1/4 watt carbon film. C403 10µf/ 25v (Z) could be shorted as well.

Also, D402 and R403 test ok.

 

[TommyW]

What voltages do you see at the base of TR401 and 402?

So the relay has been engaging most of the day and when it does, the voltages on TR401 and TR402 are very close to the voltages in the service manual. This evening it did not engage again and the base of TR401 was 6.3v and the base of TR402 was 5.5v. When I went to take a second reading on the base of TR402, the voltage shot up to 12.5v and the relay engaged instantly. This is after it had been powered on for 3-5 minutes. Would a TIP31C work as a direct replacement for the 2SC789? I have a few of those handy.

 

[avionic]

Would a TIP31C work as a direct replacement for the 2SC789?

Yes