#1
hi,

I've got a Wharfedale (Albion in USA) TCT 100H head, plugged into it's wharfedale head. I know many people may not have heard of this amp so here's a link to their site

http://www.amps.wharfedale.com/Products/product/tabid/83/PID/8/Default.aspx

My problem is, on the power amp channel I have the gain turned up all the way, and after a while half the distortion and general sound just drops out and it sounds horrible, I thought it might be my guitar as I put new pick ups on it, so I tried it with another guitar and it does the same thing.

To get it working again I have to turn it off and leave it for 10 minutes then comeback to it.

I'm wondering if this has happened to any other amps? and if there is something I could do to remedy it.
#2
Does the manual tell you which tubes are used by which preamp channel? This is either a bad preamp tube or a resistor in the preamp heating up and coming loose when the amp gets hot.

To check the preamp tubes, either buy a new tube, or pull out one of the preamp tubes from the clean channel (since it works) and swap it out for each of the dirty channel tubes. If your manual doesn't tell you, just pull a tube and see which channel works. The preamp tube nearest to the power tubes and the one farthest from the power tubes are shared by both channels, so don't move those. Your head has five tubes so one of them should just be a clean tube and the other two should be dirty channel (although it may have a different setup; one of them may be for the EQ, or shared between channels).

As you can tell, it would be a lot easier to just buy one new 12AX7 and swap it out for preamp tubes 2 through 4 until the problem goes away. If it doesn't, it needs to go to a tech to have the preamp resistor joints redone.
#3
I'm not completely sure what you mean, but I know the EL34's are on channel B and the ECC83's are on channel A. And I'm using channel B when the distortion drops out, Channel A on clean still works perfectly fine.

You say it may be a resistor, would that be an easy fix if it was?
#4
I read your question wrong. However:
There's no such thing as a power amp channel. Your amp has two preamps (A and B) and a power amp, which uses one 12AX7 (aka ECC83) and all four EL34s. That's where I misread your post - I thought you meant that one of the channels did not work, and one did.

Anyway, my answer is the same, except that if both channels are not working, you can't swap preamp tubes like I said, you'll need to get a new one to check.

It does sound much more likely to be a resistor, though it could be in the preamp or power amp sections after rereading your issue. Power amp is more likely since there's more heat there. Take it to a tech to have them check it out, it's not something you should go poking around your amp trying to find yourself.