Marshall TSL100 head model year 2001

[st220]

I have a problem on the Pre-amp side & suspect BR1 is at fault, looks that when under load the power supplied by BR1 drops too low for the tubes to operate.
Can anybody tell me the DC output voltage from BR1 when it's functioning properly?

[booj]

I've seen several of those BR1's go bad. Funny thing is they don't generally short out. They just no longer produce enough rectified DC to operate the tube filaments. I've also seen this problem caused by bad solder joints in the filament supply circuit.

[Alex R]

Can that happen to rectifiers? Genuine question.

[Enzo]

I have of course had to replace heater bridges before, but MOST of the time I get vanishing Marshall heaters it is because the solder never actually gripped the leads of the bridge when the board was made. The legs are oxidized and were not wetted by the wave solder machine.

I extract the bridge, take an abrasive to the legs to get shiny metal, and resolder them in, and they don;t come back. But really, the bridge has to come out for that anyway, and they are cheap, so if the bridge is potentially the problem, just solder in a new one. Make sure the legs are clean metal before you start.

I've seen shorts, and opens, and intermittants, but I don;t think I have ever seen a "weak" bridge.

[st220]

Thanks for the info guy's but i'm fairly sure it's BR1 because i found 1 of the pre amp tubes had a bent pin touching down to another.
Anyhow the board is one of those that has fluctuating BIAS so i.m going dump it and replace with a version 10.

ST