I have a Scott LK-48 that I have had about 6 months.
It has worked fine, but one channel in the phono stage
is dropping out. The other functions (CD, i.e.) are fine.

Is this likely a capacitor problem, or could it be a tube?
Which tube, if so?

I thought this amp had been re-habbed, but I looked inside it today
(I hadn't done this before, because it had simply sounded/ worked great)
and it looks mostly original. I hate to say this (as I will be told to replace them), but the caps are original.

All of the pre-amp tubes are Telefunkens, as a matter of trivia.

Bottom line question: "What could cause a drop out or decay in a phono-stage channel"?

Thanks,

Phillip Beard

swap the phono stage tubes and see if the outage follows the tube. My guess is that it's either a dirty socket or your switches need some deoxit.

Sorry to waste time with the earlier post.
I thought I had eliminated cables as a problem;
it was a socket problem. Not electronic.

Nah, it's not the cable/ connector. There's an as-yet-undefined problem
in the phono stage. I can't get any connection problem to repeat.
Sometimes the signal in both channels abruptly decays, sometimes just one.
The rotary switches seem fine.

DANGER DANGER WILL ROBINSON.

Is this amp labeled to use 7189 output tubes (as opposed to saying just EL84 or 6BQ5)? If so, has the bias supply been rebuilt with a new rectifier (diode or diode bridge) and new capacitors? In these amps, the same supply is used for the bias of the output tubes and the heaters of the phono preamp.

You may be getting a warning sign, that something VERY BAD is going to happen if the amp isn't serviced soon... the supply may be dropping out enough to cause one or more of the preamp tubes to shut down. If this is happening, this will be followed by the output tubes starting to red-plate (overload). This, if left unchecked, can get expensive to fix. It should be a routine repair, now... so, if it hasn't been done, it SHOULD be done immediately...

Regards,
Gordon.

Gordon--
Thanks much for the post.
Are you saying the amp SHOULD have its bias supply rebuilt with a new rectifier (diode or diode bridge) and new capacitors?

If it has 7189 output tubes? (I am pretty sure it does--)?

Or are you saying, if this HAS been rebuilt, I should look out for X?

In my cursory investigation of it yesterday, I was surprised to see
what looked like original stuff. I saw no signs of rehab or retrofit anywhere.

What should I look for to cinch the question of the rectifier?

PL Beard