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apw · 10-28-2008, 02:52 PM

Sounds like you have the drifting bias problem that this model suffers from, You need to take it to a Marshall dealer and get the main board changed, the part is only available from Marshall. When the amp warms up the main PCB acts like a NTC thermistor (YES The PCB Board) this causes the output tubes to draw more and more current until they destroy themselves. The only fix for this is to change the board and another set of OP tubes.

The aluminium tube has a tube (Valve) inside it, the aluminium is to screen the tube inside.

I repair about 2-3 TSL122 per month, When I see one of these with a blown HT fuse I replace the PCB with one of the new type as a matter of course, I've been bitten by TSL122’s too many times. I work for a Marshall Dealer in Kent in the UK.

If Your in the UK PM me as I may be able to help.

10-28-2008, 02:52 PM	#2 (permalink)
apw Junior Member Join Date: Oct 2008 Posts: 6	Re: TSL122 Blowing Mains Fuse Sounds like you have the drifting bias problem that this model suffers from, You need to take it to a Marshall dealer and get the main board changed, the part is only available from Marshall. When the amp warms up the main PCB acts like a NTC thermistor (YES The PCB Board) this causes the output tubes to draw more and more current until they destroy themselves. The only fix for this is to change the board and another set of OP tubes. The aluminium tube has a tube (Valve) inside it, the aluminium is to screen the tube inside. I repair about 2-3 TSL122 per month, When I see one of these with a blown HT fuse I replace the PCB with one of the new type as a matter of course, I've been bitten by TSL122’s too many times. I work for a Marshall Dealer in Kent in the UK. If Your in the UK PM me as I may be able to help.