What do defective phono tubes sound like?

Another possible source is the unshieled proximal part of the tonearm cable, Purist Venustas in my case, hooked to Graham Phantom, being too close to phonostage and picking ground loops and discharging loud pops. When I separate the tonearmcable from phonopreamp the noise and pops disapear

SirSpeedy,

Any chance it's mistracking? (I know you'd have recognized that, but thought I'd cover all the bases.)

Diagnostic question: do these pops happen in both channels or just one?

I'd put a small wager on a loose connection at the cartridge pin(s). Check those carefully for tightness and clean the pins and clips. For cleaning gold, see the last paragraph.

We had a similar LP-only problem last winter, in the R channel only, which made diagnosis easier. Turned out to be slightly spread connectors in one pin holder of one tube socket in the phono stage. I tightened the two clips carefully with a fine tweezers and the problem was resolved. So when you pull your tubes check the connectors in each hole before reinstalling, and clean all the pins and pin holders of course.

For cleaning gold connectors Paul recommends (and we use) a very gentle rubbing with a paper towel. Nothing stronger or more expensive is needed, nor does it require any chemicals. Gold oxidizes in a layer that's basically one molecule thick and it only takes a gentle buffing to remove. Do NOT use a Magic Eraser! ;-)

Good luck,
Doug

What is suggestesd to use to clean tubes and sockets?

Once again thanks for the interest in my dilemma.
Jloveys,my entire system is on regenerated A/C,and dedicated lines,so something like a "refrigerator" kicking in should not be a cause.If I need to go to "that" level of forensics to diagnose a problem,then I think my time in the hobby may be running out.

Doug,nice to hear from you,as you always seem to have some inner input that I might find interesting.Yes,I have checked almost everything you mention,with the exception of tube sockets.
This will be addressed this week.My new cartridge worked flawlessly with my previous arm,so that is out of the equation.I just cannot see how anything about the arm can be the culprit,but who knows,and I have gone out of my way to be respectful of the mfgr.I hope this does not backfire on me!
One "serious" concern is if I blow my tweeters,there is NO replacement for them,as Avalon is looking for a new supplier,and mine are not made anymore.I cannot "live" without "this" speaker,it is "that good",so I shudder when I power up under these circumstances,even with a very low volume setting.
Of course the more I think about this,the more obvious it seems that the tubes are the culprit(only three),but I am guarded here,as I am getting quite insecure about reliability these days."These" super systems are really quite complex,when looked at closely.
You know how happy I was with my old arm,and "if" it is the new one,which took me three months to get(without the old arm,as it was sold to finance the "new")I am going to be a "very unhappy camper".I have had alot of analog down time,since selling my "as you know",beloved previous arm(there is a lesson here).
I really need to put some finality on my upgrade path,and go back to being an LP collector/spinner again!
Of course I DO realize this will all come to a happy ending(I hope)but right now I'm about as down on the hobby as ever.I'm also(really)getting more of a workout Fotzing around with my set-up,than I get in the two hrs I spend at the gym,four times a week.

Best to all

Keep your chin up SirS. Friday night our system sounded terrible. No life, no snap, just dull, dull, dull. I gave up and we went out for dinner. Yesterday I realized I'd moved VTF in the wrong direction. Doh! When I fixed that the music all came to life again. I rewarded myself by demagging some power tubes. Woh! Just like Dan_Ed told me. :-)

I know what you mean about the tweeters in your Avalons. I'd be sick if I killed one of our diamond tweeters but at least I could get a replacement. Like you I don't think we could stand going back to something slower, we are so spoiled. ;-)

Cte500 - if your pins/connectors are gold (plated), read the last paragraph of my previous post. If they're not, a different answer might apply.