Dead Channel 101

[Zippy]

I need some help.

I am currently working on my newest acquisition, a National RX-5700. The major problem with the National is that one channel seems to be completely dead, I can't get anything out of it. I opened it up but couldn't really spot anything suspicious or obvious like all of the speakers cable being torn or anything like that. The only thing I've done so far is I cleaned the contacts which, while having been a general issue, of course didn't help the dead channel. Usually when it's only the contacts you sometimes get some noise at least.
Another thing I noticed is that the bass and balance controls are unstable - if that's the right word to describe it. Might the channel be dead due to a problem with the pots?
Are there common clues which can indicate where else the problem could be?

Any help is much appreciated I'd really like to get the 5700 back to full capacity

Thanks!

 

[baddboybill]

Have you tried cleaning or testing headphone jack???

 

[Zippy]

I new I forgot something. I just tested the headphone jack and while the balance and bass control work smoothly there still isn't any sound coming from the left channel Both VUs are working properly. Am I right that this means there's something wrong with the amp?

 

[mmcodomino]

Did you also spray the record bar?
Does the RX5700 have any other outputs for ext. speakers? Those could be reponsible for the dead channell too.
If not, I would suspect a bad pot. If both VUs swing, I would conclude that the amp is okay....
Did you try line out? I have a similar issue with my RT-S93...line out is fine and both VUs work but the right channel is completely dead. I strongly suspect the volume slider...
Anyway, good luck!

 

[Zippy]

I only sprayed the knobs and switches so far. But I have to open the 5700 up another time anyway because I forgot to put in the renewed wireless mic button. Then I'll be more thorough cleaning everything. And I'll check the line and external speaker outputs, too, thanks for the advice! Good to hear you conclude the amp's alright!

 

[Superduper]

Good to hear you conclude the amp's alright!

I don't concur with that finding. I believe the 5700 meters are VU and not power meters, and if so, then whether or not they function has absolutely nothing to do with whether or not the amplifiers are working. So it would be a great leap or shot in the dark to arrive at that conclusion.