Yamaha C-80 Pre-amp one channel low Volume == NEED HELP ==

I need help wise guys......

I have Vintage Yamaha C-80 Pre-amp and this was working fine till last week. Earlier this week I noticed that the volume on left channel is about 50% less as compared to right channel. All other functions (Bass, Treble etc) are working fine. I'm not too Knowledgeable about electronics but do have a solderingIron, Digital multimeter and other tools to carry out basic troubleshooting. Sofor I have noticed following:-
1.Problem is only with left channel.
2.All inputs have same problem (Tuner, DAT, Aux….)
3.If I connect output to Tape output 1 or 2, thevolume on both the channels are normal (both at 100%
4.But if I connect output to pre-out (normal orinvert), Right channel is 100% and left is 50%.
Please help.
Service Manual is available here

Yamaha C-80 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine

Most likely a dirty switch/control (deox-it) or a cold solder connection.There are a bunch of copper buss bars within the pre-amp. SOP is to reflow the solder on all of the printed circuit board/ buss bars connections with a little fresh solder. Also hit all the RCA jacks where they connect to the circuit board with some fresh solder.

Tapping around on the circuit board with a non-metallic probe while listening at low volume may very well reveal the 50% left channel issue/ root cause.

Hello
Does this trouble subsist if you increase to high volume like in situation of bad contact in relays ? Does the sound go back to normal level ?

:scratch2:

Silly question maybe, but you checked the balance knob right? I've moved the balance knob more than once on accident and wondered what was going on.

Chris Brown said:

Silly question maybe, but you checked the balance knob right? I've moved the balance knob more than once on accident and wondered what was going on.

Click to expand...

Hats off to you chris. sounds silly but thats exactly what it was.....three cheers to you guruji......

Great outcome. I love problems that go away.

Must admit that I've fallen victim to this with my C-80. More than once