SWR LA 12 Bass amp inop. Powers on, only humms

[2222]

SWR model LA 12 60 watt bass amp powers up but only hums (suspiciously like 60Hz?). A friend gave it to me to, thinking I might be able to fix it.

One chassis attachment screw is missing, and others show marking that it has been opened up previously.

At first it almost started to amplify a test signal, then it started thumping the speaker several times per second. When I powered it off it let out a squeal that rose in pitch until it quickly faded. Insides have a faint burnt electronics odor.

I may have identified what looks like a dry solder joint at the (marked "+") leg of what is labeled BR1 (bridge rectifier?).

Photos to follow.

[2222]

Preamp photos

[2222]

Power amp photos



Detail of possible dry solder joint on BR1 "+" leg.

[p.larner]

maybe it doesent know the words to the songs?,couldnt resist that! lol.

[2222]

Good one!