Pre has a channel out....I think.

deronb1

No sound from the left channel on a Kenwood Basic C2 pre in stereo mode. It works in mono and both the left and right meters on my amp move, but in stereo just the right channel works. Any thoughts?

mhardy6647

All sources?
Have you tried "fiddling" with all controls?
Fair likelihood that the issue is a dirty (oxidized or corroded) switch or pot. That's a very good preamp... but it is 35 years old or so. If it hasn't had the controls cleaned recently... it wouldn't hurt to do it. You can do it yourself; get a can of DeOxit D5 from (e.g.) www.partsexpress.com (or your favorite vendor). You can find, if memory serves, a "Sticky" on cleaning pots and switches in one of the forums (DIY?) at www.audiokarma.org

deronb1

mhardy6647 wrote: »

All sources?
Have you tried "fiddling" with all controls?
Fair likelihood that the issue is a dirty (oxidized or corroded) switch or pot. That's a very good preamp... but it is 35 years old or so. If it hasn't had the controls cleaned recently... it wouldn't hurt to do it. You can do it yourself; get a can of DeOxit D5 from (e.g.) www.partsexpress.com (or your favorite vendor). You can find, if memory serves, a "Sticky" on cleaning pots and switches in one of the forums (DIY?) at www.audiokarma.org

Good idea. Actually, it is very clean inside and I did blast it with compressed air. It is happening with both phono and CD. The stereo/mono button is just that, a button. In for mono and out for stereo. I'm assuming the mono is controlled by the right channel. When balance is in middle, both speakers play and when I turn it to the right, both speakers play with no change. When I turn it to the left, there is no sound out of either speaker.

mhardy6647

Mono blends the two input channels; typically you'll get the sound from your "good" channel (Right) out of both channels in the case you describe.

Dirty controls won't necessarily look dirty - the oxidation they suffer is air-borne and often not related to dust or dirt.
Check this link to various threads, including one on deep-cleaning. That latter thread should at least touch on the use of DeOxit (the best contact cleaner readily available nowadays): http://www.audiokarma.org/forums/showthread.php?t=426532

deronb1

mhardy6647 wrote: »

Mono blends the two input channels; typically you'll get the sound from your "good" channel (Right) out of both channels in the case you describe.

Dirty controls won't necessarily look dirty - the oxidation they suffer is air-borne and often not related to dust or dirt.
Check this link to various threads, including one on deep-cleaning. That latter thread should at least touch on the use of DeOxit (the best contact cleaner readily available nowadays): http://www.audiokarma.org/forums/showthread.php?t=426532

Ok, will do. Thanks.

deronb1

Any other ideas than an oxidized contact? What are some other things that could cause this?

ViperZ

Have you tried different inputs? Clean all inputs, switches, pots. If you get OUTPUT out of both channels, even in mono, it may be as simple as some switch being dirty (I just had this exact problem on old Dynaco tuner). Obviously, worst case scenario, something in electronic circuits went wrong, but I wouldn't rule out a simple fix first.

BlueFox

deronb1 wrote: »

Any other ideas than an oxidized contact? What are some other things that could cause this?

A 35 year old pre-amp, maybe a part failed.

depthsounder

I know this is an old thread but I'm trying to share a fix for this common problem.

The wipers on the balance pot have a tendency to break free from the plastic disc that they are attached to. See the page located here:

http://www.drmaudioht.com/tektips.asp?pg=14

You can fix them with some superglue. I removed the potentiometer from the board when I did the repair though I read that may not be necessary. I used a pair of small wire cutters to gently pull out the two aluminum rivets holding the end plate on the pot, then removed the e-clip from the shaft. Disassembly of the pot body is fairly easy to figure out, and it only goes back together one way (correctly).

The plastic disc in the center of the pot is what holds the wipers. Glue the wipers back on and you are in business.

This did not fix my C2 entirely. I had to spray contact cleaner in the the input selector and work it back and forth to get it working properly.