Adcom GFA-555

[claiborne]

I just got a Adcom GFA-555 with one dead channel practically given to me. I opened it up and found that both the fuses on the transistor boards on the right channel are blown. Can anyone tell me what the proper size/kind of fuses they are? I looked at the markings on the fuses and it doesn't give the type. Thank you!

-claiborne

 

[SY]

6 amp, fast blow (AGC).

It may be worth looking to see what caused them to blow...

 

[Bigred]

Yes I agree with SY; do yourself a favour and DON'T just replace the fuse and try it out with your fingers crossed. Check the physical condition of the fuse ATLEAST. If it looks like a light blow your probably safe.

 

[claiborne]

Thanks,any idea what I should take look at first? Is there a common cause of blown fuses on these amps? Something that would take out both fuses on one channel at the same time.

I gave it a very careful visual inspection and nothing looks at all damaged or burnt.

This the first solid state amp that I have tried to troubleshoot. Any quick tips you can give me would be greatly appreciated. Thanks!

-claiborne

 

[claiborne]

fuses

One fuse looks like a very clean blow but one does look worse with a little black circular burn mark on the glass. Any ideas?

 

[Bigred]

On that basis it sounds like you have a short(s). The power supply, outputs and drivers are places to start.

 

[claiborne]

Fuses

I pulled the fuses out of the other channel and also rechecked the blown ones with a magnifying glass. Someone has used 10AMP 125volt fuses on both channels and the main fuse on the real panel.

Are these the correct values or has someone put the wrong ones in?

Sy,

You mentioned a 6 amp, fast blow (AGC) is this the proper rating for the main fuse also?

Once I get the proper plugs in place should I try to turn in on with a 100 watt bulb on the power cable? I am in no hurry to turn this on and I want to be a cautious as possible.

Thanks!

-claiborne

 

[claiborne]

Replacement fuses

I looked at my local parts supplier and they only had fuses rated at 250v the originals were 125v.

If the AMP and fuse type are the same is it OK to use the 250v in place of the original 125v fuse?

Thanks!!

-claiborne

 

[djk]

250V fuses are fine.

Driving certain Infinity speakers will cause the fuses to blow, and frequently the drivers too. If the fuses are the correct value the outputs are generally OK.

If someone had 10A fuses in there though, the driver transistors are probably blown, and maybe some outputs too.

Do a search on 'light bulb' and fire it up with a 75W~100W lightbulb in one side of the line.