Valve preamp balance skewing to the left

I recently bought a Bel Canto SEP-2 valve preamp (http://www.goldmanaudio.com/goldman/productmfg.asp?sku=7) 2nd hand. It's been internally upgraded to SEP-1 status. It sounds great and worked fine to start with, but over a period of a month or so the balance started to skew to the left. Interestingly, the device itself seemed to detect this bias as when you switched it on, the (microprocessor-controlled) balance control would automatically be set to the right in compensation. If you reset the balance control back to "centre" position, the sound would be clearly offset to the left.

This effect seemed to get gradually worse over time. At first it was barely noticeable, but by now it's very obvious. The "automatic compensation" of the balance control seemed to react accordingly, initially just setting itself one or two "ticks" to the right on startup, and by now setting to the maximum (6dB?) setting to the right, though this isn't enough to compensate for the effect anymore.

I've tried swapping tubes and the effect remained, so it's not simply dying tubes. Can anyone think of anything else that might cause this? Is there anything I can do to fix it? It's clearly out of warranty, so if I can avoid the cost and hassle of shipping it back to Bel Canto in the US for servicing I'd be very grateful!

Any thoughts or advice would be greatly appreciated!

Cheers,
Dunc

P.S. - Sorry for crossposting on PFM, but I'm rather desperate!

 

Don't tell Mr Marjoribanks. He'll never notice!
Maybe try resetting the balance to centre according to the front panel and then switch off for a while.

 

don't want to get in the way of this urgent discussion, but Duncan, I see from your sig. that you've invested in a Dax Decade w/b!! Did you get my PM, btw?

 

Argh! I sent you a big long PM detailing my exploits over the past week or so but it seems to have evaporated into the Big Inbox In The Sky... Instead of rewriting it (or hijacking my own thread) I think I'll start a new thread in the Reviews section...

Dunc

 

I have a dirt cheap chinese valve pre thats been doing the same ...I thought it may have been the ecc81/82 's but after changing them and getting a better sound it still will drift. I've not had time to do an indepth hunt ....but if I find the problem I'll let you know.

 

Thanks Zanash.

Been in touch with Bel Canto, who think the control board may be fried, possibly due to static discharge of some kind. Good news is, it should be possible to send the board back on its own, which will cost a lot less than shipping the whole pre!

Dunc

 

now that is good news for a piece of consumer goods - they will replace the board! although not every consumer would be confident about replacing the board. still, a good thing.

 

Hum... thats not going to help me ! I was thinking move of a dry joint somewhere in mine....as the get hot the joint opens etc.