Is my phono stage stuffed

Hi. I have a MF NuVista M3 Integrated amplifier. As of yesterday the left channel of its phone stage has dropped out either altogether and just a emitting a faint scratching sound and occassionally it comes back to normal life but for a minute at most.

I believe it to be the left channel of the phone stage because:

1) I get sound out of both speakers when the source is switched to CD;

2) I switched the tone arm cable plugs at the phono stage RCA input terminals - left with the right and vice versa and still there is no output of the left speaker.

3) I double checked the grounding of the tone arm to the grounding of the amplifier. At a very low minimum volume I induced the typical "hum" generated by not grounding but the hum only occurred in the right speaker not the left.

Any ideas anyone? anything else I should check test. Unfortunately I have no other phono stage to check if everything else is working as it should be.

I have a NuVista preamp and at one time the selector switch was causing a similar problem. It was resolve when I opened up the preamp and gave the switch a shot of cleaner. (this issue also happened with a marantz preamp I had years ago).

The only other "simple" check is to verify the issue isn't with your cartridge. If you have another table you can plug in this would be a quick check. Or plug your table IC's into another input and see if you have a signal from both channelsvfrom it. It will sound bad and faint but you should may be able to hear if you have a signal. If the table is the source, the solution may be as simple as remove-clean-replace your cartridge headshell leads.

If none of these work you may either have a bad cartridge, or something more significant going on with your NuVista. My money would be on the selector switch being your problem.
The spray stuff is not a permanent fix. Repair it properly.
. . . respectfully disagree. Why would you replace a part that only requires cleaning? If you spend a ~$100 to replace the selector switch (if that is indeed what's wrong) it's no less susceptible to getting dirty again than the cleaned one.
Just had the same problem with an Audio Research pre-amp.Played with selector switch,moving it alittle bit each way and presto, full sound. Gave it a spritz,good as new.Always try the simple fix first before dishing out some cash.
>>05-14-09: Stringreen
The spray stuff is not a permanent fix<<

This is poor advice.

No cleaner is a permanent fix because most controls and/or switches will require occasional maintenance.

There is no need to replace any switch or control mechanism when a simple cleaning alleviates the problem.