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Adcom GFA-555 fuse stuck


Hi there,

I've got an Adcom GFA-555, which I use with a pair of Infinity Kappa 8 speakers.

I was running pretty loud on some low frequencies, and I lost all power from the amp. I figure the Kappas were just drawing too much current, since the woofers can dip down to around 1 ohm with low frequencies.

The power light doesn't turn on, so it shouldn't be thermal shutdown or the transistor fuses. I opened up to check, and they are all fine (I put in 4.5 amp fuses instead of the 6 amp ones spec'd to give me a little safety room). After cooldown it still won't turn on.

I didn't see any scorched components either, but I know from personal experience that that doesn't necessarily mean that there aren't any burned out components. I don't smell anything, at least.

So I'm pretty sure the problem is that the power fuse is blown. The problem is, the screw-in plastic holder is cracked in a couple of places, making normal extraction with a screwdriver impossible.

I thought about trying to super glue it, but I doubt that would hold (and I don't have any on hand any way). I suppose I could epoxy an old screwdriver on to it...

I'm pretty stumped as to what to do - I generally tackle this kind of stuff myself, although at this point I know I need a replacement holder in addition to the fuse anyway.

My only thought is to take it to a general electronics repair shop - there's no real audio repair shops in town AFAIK, and the nearest Adcom authorized repair shop is an hour and a half drive away. As long as it's just the fuze, it shouldn't be that difficult of a job - which is why I'd like to do it myself if possible.
blackbeardben
blackbeardben OP
16 posts
 
That's a great idea. I didn't think about epoxying something else to it - I've got a spare knob that might work well. That way I'd never have to worry about using a screwdriver for it again.
ghstudio
141 posts
 
Good suggestion...just be very careful not to get the glue/contact cement you use on the outer ring.

Alternatively, instead of cutting a slot for a screwdriver in a plastic disk, you might use a plastic cylinder about 1/2-3/4" long and the right diameter..and then turn it with a pliers or your fingers.
theo's avatar
theo
2,658 posts
 
If anything take the fuse holder completely out of once you remove the cover and can access it. Go to a local electronics store e.g.Radio Shack, etc and buy a replacement fuse holder. That is a very standard fuse holder. It is most likely using a plastic nut on the inside of the rear panel to keep it sandwiched to the panel. Take a sharp utility knife or a Xacto knife and cut the nut, push the holder out undo the solder connection and wah-la, put in the new one and it will still look OEM.
srwooten's avatar
srwooten
694 posts
 
Heat up a standard screwdriver hot enough to melt plastic and melt it into the rear of the fuse holder, remove, let cool, then insert the cooled down screwdriver into the new (now hardened) slot, and unscrew.
blackbeardben OP
16 posts
 

Well, I extracted the whole fuse holder after the cover split apart on me - the nut and washer holding it in were brass, actually. It also turns out that there was a crack in the holder body as well. It must have been overtightened last time the fuse was replaced. I never actually got the fuse itself out though.

The hardest part was working around all the wires - I worked from the bottom to minimize that.

I had to cut the wires that were soldered in - there was no way I was going to unsolder them as they were rock solid with wires wrapped around very well. I suppose I shouldn't expect anything less for a power source that's supposed to handle up to 1000 Watts.

I'll go to Radio Shack in the morning and pick up a new one and the 10A fuses I need. It shouldn't be too hard to solder it back in - I'm used to soldering on delicate PCBs rather than thick wires.
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