I assume that by checking cables you also swapped the connections to the amps at the pre?

I assume this is happening both with phono and another source? This would eliminate something in the phono stage as the issue.

If so, then the easiest trouble shooting is to swap the positions L/R of the valves, one set at a time, powering off in between. Start with the rectifiers, then the tubes in the line stage. If you hear the failure switch channels, you know that tube is bad.

If after doing this the problem doesnt flip channels, and all the cable connections are not bad, you know you have another part failure in the line stage that you will have to seek out a reliable repair for. Probably the best place to start with that might be A23.

** If I may just ad one precaution. After you power down the Giscours, I would wait like 5 minutes before powering back on. So following Gortnippers procedure above, also give the preamp that rest before powering back up. So I would shut down, let the tubes cool a few minutes, put 1st set back to original position, flip second set, power back up....

Thanks fnj04,
Im going to try this tomorrow might once i locate my hex screw drivers!

Regards,
Paul

Paul,
be patient. It takes a lot of time to unscrew all of them :D !

Thanks Jerome,
Im very protective of my little green beasts, and i want dont want to scratch or ruin a thread, extra care is called for! I also has a spare rectifier set that the previous ower was kind enough to give me so fingers crossed!

Geez- Wouldn't that be cool if it were those rectifiers. I believe the Allen size you need is 2mm. Make sure to drink Chamomile before you start the process. :-)

Frustration continues...

Started the task of carefully removing all 26 2mm hexagon screws from the top of the unit, after removing 25 i came to the last screw which, in pre-purchase activity has developed a worn/stripped head and i cannot remove it, tried the rubber band over the screw driver trick but cannot get it to move. The head of the screw is close to circular!

25 down and one to go is really frustrating and it looks like tube swapping across the channels is not going to be achievable by myself, scratching head time, looks like this needs to go to somebody more qualified than me since i cant think of removing without marking the green beastie.

This happened to me once with a Copland CD player. Very frustrating !
Sorry Paul.
I would drill the screw out, with a dental bur if I had your unit on hand, or I would grave a new cross in the screw to grab it with a cross screwdriver.
It is not very tough to pull out a screw with a damaged head. Maybe you can ask your carpenter....or your dentist :) !

Some more suggestions I found...this one involves something like super glue..of course if I recall the darn screws are really tiny...

Use JB Weld or equivalently super strong “welding” adhesive to attach a nut to the screw head. Pick a nut that is about the same size as the screw head or at the least such that the diameter of the hole in the middle of the nut is smaller than the diameter of the hole in the screw. Now place the nut centered on top of the screw. Fill the hole with JB weld, being careful to not let it run everywhere. If the nut is flush on the screw, this shouldn’t be a problem. If it can’t be flush, use some sort of quick drying temporary gasket or the like to seal around the edges so that the JB weld doesn’t get everywhere, but rather just stays in the hole. Now let it dry the recommended time. Once it has hardened up, use a socket wrench on the attached nut to remove the screw.

Read more at The 12 Best Ways to Remove Stripped Screws

I was wondering if this would happen.

No, this wont work - . I tried that. The best thing to use is a screw extractor - Screw extractor - Wikipedia, the free encyclopedia

Get one that fits into the stripped hole and you can do it gently by hand. They work well.

If there is still a bit of grip in the screw (you might try a non-metric size allen head or a different shape head if you have a set of screwdriver tips) and have someone assist you by gently lifting the top plate of the pre and rotating it counter-clockwise to "help" the screw out.

Thanks, I stand corrected...sometimes the best laid plans of mice and men....damn I should have gone with the screw extractor (item #3).