How to Identify which Is the

Thanks for the responses. I switched the out connectors to the CDP, per Niravp's suggestion. What I got was a dead right channel, and a very distant left channel (not the volume level the working channel previously had at all).
Newbee, I first tried switching a tube in the preamp for a new (6922) one, since it did not light up. Now everything lights up, but still the problem remains.
I didn't mention that I added a PS Audio P500 power regenerator into my system a few weeks ago. The prior two times I used it it flashed "fault" when first turned on, then was fine when turned off and on again. Could this be causing the problem(s)?

Well it doesn't sound like your power amp - if that were it you wouldn't get anything out of your left channel. Should be the same for the preamp which would leave the problem in the CDP. You might try plugging the CDP into a different set of inputs on your preamp and see if you have the same problem with the CDP - if not then the problem is probably with the inputs on the pre-amp. If you have another source, such as a tuner or another DAC or CDP you could try it an see what happens - using the same inputs and another set of inputs. I'd guess that there might be an intermittent ground fault somewhere and that is what causes the P500 to flash on & it could be as simple as a shorting in a solder joint in an female RCA on the pre-amp or CDP (has happened to me ofter and is why I recommended using a seperate set of inputs) or a cracked solder joint on the interconnect itself. Try sub'ing in a new interconnect. Keep us posted.

Thanks for the responses. As of this morning , it was a very distant left channel, and no right channel.
I tried a different (borrowed) CD Player-SAME RESULT.
I tried reversing the CDP out to the preamp--same result.
I then tried reversing the L and R to the power amp from the pre-amp--same result.
Then, I switched the speaker cables to the speakers.
Now, I have a good-sounding normal volume left channel, but still a dead right channel.
Any other ideas? Does this indicate a bad (now, right)speaker cable; a bad right speaker, or what?
(Yes, I know it was initially a dead left channel--this is wierd)!

Thanks
Steve

Your original description of how the channel went out is very typical of what occurs when you have a sudden power tube failure (as I mentioned above). If you haven't done so, check out your amp.
You could have a short in your cable or the posts on your amps and speakers - check your cables for shorts and stray pieces of wire at the ends which could cause a short.
I have zero knowledge of the type of cables you are using BUT some cables do not go well with some amps - They can actually cause damage, its not just a matter of tone. Be sure you have an appropriate match. You might also try using another set of cables and see if that makes a difference.
Check the amp!

FWIW; I has a similar problem a few months ago and it nearly drove me nuts. It turns out I had a bad interconnect from the source (phono-pre in my case) to the preamp, and a bad tube in the phono-pre. I finally found it by getting a spare IC (only one!) and testing first one channel then the other, one connection at a time, then trying the bad IC on another source. After that, tracking down the tube was easy (nothing left to look for).