I was given an Adcom GFA-555 that was reported to be not working. I checked all fuses and wiring and components visually for burned resistors bulging caps etc BEFORE plugging into the DBT. I am using a 100W bulb. When I plugged into the DBT to test the amp the lamp lit bright and slowly dimmed but not completely dim, with the power button in both the on or off position. How should I begin to proceed with this repair, and should I assume the switch is fried or that something in the amp is shorted?
Unplug the amp, and use a meter to check continuity across the power switch in both positions.
If it's stuck shut, replace it.
If it's stuck shut, replace it.
I'm 120VAC area. I replaced the .01 cap but it still turns on with the switch in either position. I moved up to a 150W bulb for the DBT. It dims down OK with the 150W.
Yes. Just measured both sides of the switch. Pictures show the left side IMG_1297 that is measuring .17Ω in either ON or OFF position. The other two photos IMG_1298/99 show the opposite side of the switch measuring OL in the OFF and .22Ω in ON position
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Referring to my post #2, I would have been done already with this simple repair.
Yet... the posts and discussion continue.
Yet... the posts and discussion continue.
City Of Brotherly Love. Dude, you're fantastic. I'd be proud to be done with this simple repair too.
Replace that power switch as wiseoldtech already suggested. It seems a Marquardt 1835 will fit. Please check physical properties and I can recommend these, plain good European quality.
The 1835.3108 is a version with green light. I have about the same black version in stock but I am in Europe.
The 1835.3108 is a version with green light. I have about the same black version in stock but I am in Europe.
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It's a common issue for the GFA-555. The in-rush current is pretty large and it welds the power switch shut sometimes.
Original part is Carling RGSCC901-R-B-B-E, in stock at mouser.
Original part is Carling RGSCC901-R-B-B-E, in stock at mouser.
That's correct.
I've had to replaced them as well.
And that's why I posted #2, but it seemed ignored, and discussed far too much.
15 minutes to check the switch, find out it's defective, and replace it.
Job done.
I ran a busy shop for many years - I didn't have the luxury of discussing repairs.
no need to get upset, thank you for the heads up on the power switch. problem solved.
