So, the nonsense bias board arrived. It was in a properly printed Fender
cardboard-topped 'accessory' bag, as you might find hanging on pegboard in
any music shop. "Genuine Fender Parts" it proudly announces. "PCB ASSY
AUTOMATIC BIAS 4 TUBES S - S"

I'm not sure what that tells us exactly, but if Fender have them all bagged
up ready to hang up in dealers ... ??

Anyways, put it in and fired it up. It does a lot of LED flashing and bias
trimming between the 4 tubes, but seems to eventually settle on a
'solution'. Out of the four (brand-new looking) Sovtek output tubes, three
ended up with almost -ve 51 volts on their grids, and the other with just
under -ve 52 volts. For all of this effort though, I'm not sure that there
would have been any practical difference if all four tubes were to have had
the same bias on them. I don't know if these Sovteks were bought as a
matched quad - we didn't fit them - but clearly they aren't, quite. I don't
know how much 'slack' this board is able to take up, but I would imagine
quite a bit.

But the thing that's vexing me a bit now, is whether to recommend that the
owner replaces all four tubes now for a properly matched quad. There's no
signs of any flashovers or other nasties going on, but I still have that
niggling doubt that something might have ****ted that board, and that one of
the outputs clearly doesn't quite match the other three. Thing is, it's
already going to have cost them a bit in bench time, even if we let the
board go in for no cost, and to then add a set of output valves that it
looks like have already been replaced not long ago ... :-\

Arfa