VU Meter malfunctions- Yamaha CA-810

[Moer]

Dear all, I need your advice as I found my Yamaha CA-810 integrated amp VU meter does not work properly on the left channel.

- Left channel needle goes and stays at the max (furthest right) after the power on.
- Back to the min (furthest left) after the power off.
- Only happened to the left channel.
- Sounds come out normally on both channels.
- Situation remains after switching to different inputs. (Only hook up with aux for streamer)
- Needle sometimes fluctuated at the max level.
- Light bulbs work with no issue.
- Tried to unplugged and plugged the power.
- Tried reconnected the speaker cables and the interconnection.

Thank you for your advice. Not sure if the VU meter is dead. I am not a diyer and don’t have tools for testing.

Merry Christmas and stay safe.

 

[Semanon]

It could be that the trimmer that adjusts the meter has failed, or is dirty (shorted). Or one of the transistors that drive the meter function is bad. You can probably try to check the adjustment trimmer, but beyond that you are going to need to take it to shop or step into the strange and wonderful world of audio repair diy.

 

[regore]

Most likely a problem in the meter drive circuitry, not the meter itself.

 

[avionic]

There should be a power meter calibration procedure in the service manual. Try re-calibrating the meters first. If it don't respond to calibration then we will need to dig a bit deeper.

 

[avionic]

BTW welcome aboard....

 

[regore]

VR 701 is the left channel meter adjust. Hi Fi engine has the schematic. Nice, powerful amp.

 

[LincolnJ55]

Sorry ask, but I have the same problem, with so many transistors just to run a VU meter, where to start?
Anyone found the root cause? In my case, It’s not the caps or VR. I removed TR709 and the meter went backwards. (Needle moved to the left on power up)
It’s a lovely amp, they do collect much dust and the glue is so corrosive, it ate a diode!

 

[mbz]

I removed TR709 and the meter went backwards

Suggests problem is TR709 or a previous component.
Possible candidates are TR709, D703,TR707, TR705.
Measure dc voltage at D703 cathode, black meter probe connected to any black meter post. Repeat for D703 anode
and TR707base/R713/TR705c node.
You could try diode test the above candidates(incircuit ok, looking for a short), amp powered off/unplugged.