One amp channel out until warmed up

[OscarEmmy]

I use a Yamaha CA-1000 amp - the past two days, the left channel output has not worked for about 5 minutes after switching the system on. Right channel works fine. Eventually the left channel comes on and works perfectly. It's not a faulty connection, not dirty switch contacts (all checked A1)...it's just a 'warm-up' event.

The loss of left channel output is at both the headphone socket and the speaker outputs (all). I am sure a component must be failing, but am unsure whether it sounds like a capacitor, since I would have expected that to start normally then fail as it heats up. This is a reverse of that.

Anyone able to give any clues where to check first? I totally love this amp and am a music junkie, so am keen to repair it as soon as possible!

Please help if you can

 

[richamor]

poor solder joint? Expands as it heats up and makes contact?

 

[gearhound]

Or a crack in a PCB trace, that expands when hot, to make contact?

Steve

 

[shimniok]

that was my guess too... or something wrong with a protect relay if it has one.

 

[bharper]

if that amp has seperate filter caps for each channel, measure the +- rail voltages and see if one side is low. just fixed a parasound that would not come out of protect for 10 minutes, and it was bad main filter caps creating the problem (4 of 6 were vented).

 

[DanO55]

most likely

poor solder joint? Expands as it heats up and makes contact?

seen hundreds of examples in the last 35 plus years

 

[BinaryMike]

You need to rule out the protection relay first. If it has a bad contact, you can usually make it work to some extent by turning the volume up sharply. If that's no-go, then the next step is to swap channels between preamp and power amp in order to isolate the failure site. Most techs would probably proceed beyond this point by getting out the schematic and selectively applying coolant spray to those components which dissipate a significant amount of heat, and by inspecting the PCBs for bad solder joints. Sometimes careful tapping near the failure site will help narrow down the fault location.

 

[OscarEmmy]

THANKS everyone for the options...I'll check the relay first, then move on to looking for bad joints. Beyond that, I'll probably get some pro help. Seems to me this problem will just get worse with time.