Power tubes running red hot - help!

lukedlb

The amp is now home from my local tech. The Bias circuit was fried letting through the max, turning the tubes red hot.
A new pair of TAD el34s and a fixed Bias circuit was all it took to get the amp home and in top working order.
I had no idea this amp would be so loud from the get go. The volume sweep on both channels is at the beginning. Past midday it's all the same. Quite different to the earlier models which have a full sweep.
No bridging the channels on this amp, unfortunately. On the p2p earlier models, it's a great help introducing mids from channel 2 into the more fendery channel 1 (channel 2 is usually very dark, even for a marshall). However, on this 75 model, channel 2 has much more Marshall sound with the bass down low and can be used independently.
My god, this amp is loud. Right in your face, even the fender side. Plus, it can take any pedal with tons of headroom to spare. A tube screamer actually sounds great (ok, I'm slowly appreciating TS now) as the compression stays open. Fuzz really needs the guitar vol past 9 to start making an impact on the amp.
I plan to give a full run down and comparison on these much underrated amps, once I fix the rattle in the '72.

ICBM

lukedlb said:

I had no idea this amp would be so loud from the get go. The volume sweep on both channels is at the beginning. Past midday it's all the same. Quite different to the earlier models which have a full sweep.

They’re very poorly designed. There are ‘bright’ caps on the volume controls which are such a huge value that they almost completely bypass the pot.

lukedlb

ICBM said:

lukedlb said:

I had no idea this amp would be so loud from the get go. The volume sweep on both channels is at the beginning. Past midday it's all the same. Quite different to the earlier models which have a full sweep.

They’re very poorly designed. There are ‘bright’ caps on the volume controls which are such a huge value that they almost completely bypass the pot.

I can't fathom why they would do that. Any reason why bridging the channels isn't successful on this model? It's fine on the 72.

If I remember correctly from a previous thread, you used to gig one of these back in the days.

ICBM

Why can’t you bridge the channels? It’s the same basic circuit as the older ones.

The one I had was a ‘73 head with a 2045 2x12” - I used it with a band in practices but I don’t think I gigged with it, I think I’d moved on to a Club & Country by then... a much better amp in my opinion.