How to Identify which Is the

Begin with the source, and switch the left/right interconnects until you figure out which component is the problem.

For example - connect the Right output of your CD player to the Left input on your pre, and connect the Left output of the CD player to the Right input on your pre. If this setup results in a dead right channel, your CDP is to blame.

If, after doing this, you still have a dead Left channel, repeat the procedure for the pre to power connection. If this results in a faulty Right channel, instead of Left, then your preamp is the problem.

If the Left channel is still dead, then switch your speaker cables (ie, connect the Right output of your power amp to your Left speaker). If this move switches the dead channel from Left to Right, then your speaker is busted. (although, in this case I would have someone take a look at the amp to figure out why it ruined the speaker).

I am not too familiar with tubes and don't have any good advice as to isolating the problem if the tubes are at fault. I am sure there is some way you can switch paired tubes from one channel to another... but ask someone else, who knows what he's talking about.

Sounds like you blew a power tube in the left channel of your amp. Look at your power tubes - are the left channel tubes lighted when the amp is on? If not that is your problem and you must replace the left channel tube(s). You might also have to replace the fuse, and if a new tube won't bias, you might have to replace a resistor which quite frequently (in some amps) will go with the power tube.

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