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[gstirrat]

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Edited August 24, 2012 by gstirrat

[3below]

Depending on how clued up on electronics you are:

1) Take it to a good guitar tech / electronics expert

or

2) Get the multimeter and soldering iron out and start checking the circuit out


First stage - are there any op amps that are 'push fit'. If so ease them out gently and push back in. Any push fit connectors, lift off and push back on. Oxidation of connectors can often cause problems. If not fixed then;

Second stage - unsolder (unless you are lucky and there are push fit connectors) the two pickups from the pre amp board. Play the same string, measure the output voltage from each pickup. They should be [b]roughly[/b] the same. A seriously big difference suggests pickup problem.

Third stage - If the pickups are OK you now know which channel on pre amp is faulty.

Next remove the preamp from the guitar, visual inspection time

Do any solder joints look dull / cracked or sharp & pointy (Ice cream cones) or just badly done. If they do just resolder them with a spot of new solder. Try bass again.
.
If not sorted then you need to borrow a signal generator, send a test tone between 80Hz to 2000 Hz into the good channel with the same voltage as the pickups.

Measure the voltage at various points in the circuit and record [edited: write down the values] them.

Repeat on the faulty channel. You should be able to identify the point and component that is the cause of the fault.

The circuit is low voltage so it is unlikely to be a failed / overheated component.

Yamaha might provide service engineer circuit diagrams and test voltages, useful if they do.


Method 2) is cheaper, Method 1) is easier.

YMMV

Edited May 26, 2011 by 3below

[bubinga5]

could you wish for a more comprehensive answer than that....??





its what i was going to say..

[Grand Wazoo]

First port of call, have you tried a fresh battery and a decent cable?

[gstirrat]

Thanks very much 3below! Sounds like you certainly know what you're talking about.

I think I'll probably go for option 1. After taking a look inside the TRB, it's old school 1980's crazy town electronics look to complicated for me and my lack of experience!

Here's a couple of photos of it's guts.



[attachment=81076:IMG_0801.jpg] [attachment=81077:IMG_0803.jpg] [attachment=81078:IMG_0804.jpg]


Gus