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Adcom gfa-545 Broken

R

resevil83

New Member
Hello, I was wondering if anyone could help me out. My Adcom power amplifier is broken. It powers on and works, except the left output does not work. The right output sends the music to the speaker no problem. Left - nothing at all. So if anyone could give me a pointer, I'd appreciate it. This is an Adcom gfa-545
 
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I suggest you open it up and check the fuses. There is a very good chance
you will get lucky and find a blown fuse.
 
The #1 cause of "dead channel" on Adcom power amplifiers is blown rail fuses. These should be replaced in pairs, and I recommend using premium fuses like Littelfuse, rather than the many bargain fuses available today.

CAUTION: Because capacitors hold a charge, even when the machine is off, note that a blown rail fuse may have 50-70vdc across it. Careless removal can lead to sparks and component damage. Discharge the "high" side of the fuse to ground using a cliplead and, say, a 100 ohm power resistor.

Fred
 
Had the exact same problem in my 545II. Just open it up and check the fuses. I got lucky and mine was just the fuse.

And yes, discharge the capacitors before you pull them. Good luck.
 
Replace all 4 internal fuses with ceramic MDA 4 amp fuses, available online. Adcom has bleeder resistors on the big caps, wait a few minuits after powering off and take ordinary caution not to ground anything.
 
I have that model here and the BIAS control transistor ( 2sd1684) is installed "backwards" on one side of the amp
It came in that way but the output has a BIG DC offset and the bias points are 10X what the spec says

Anyone know more details about this circuit??

Thanks
 
phatterplatter said:
I have that model here and the BIAS control transistor ( 2sd1684) is installed "backwards" on one side of the amp
It came in that way but the output has a BIG DC offset and the bias points are 10X what the spec says

Anyone know more details about this circuit??

Thanks
Click to expand...
Does the transistor look factory installed by type and soldering?
 
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