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ADCOM GFA 545-II Fuse

L

Luxxy

New Member
Hello Folks:

My son blew my ADCOM GFA 545-II doing a "bass test". The AC input fuse is blown and I need to replace it. I saw a previous discussion on the fuse part # and checking to see if the other parts of the amp are OK before hooking everything back up.. I'm just trying to get the correct replacement fuse. I have reviewed the service manual and 3 fuse options are listed. I checked the web and the Bussman AGC-6/250V (for 120V) seems to be the most easily available. However, when I do the search, I get fast acting and time delay options. I talked to a guy at Fry's Electronics who said usually for music amps, you want the slow (time delay). Anybody know which is the correct one for this amp?
 
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First off, is the original blown fuse blackened? If so, I wouldn't let your son touch it ever again. The blackened fuse indicates a short somewhere else and another replacement fuse will simply blow when powered up.

Usually these things will take a certain amount of abuse but anything can be damaged when not using any common sense. Look for a manual for the correct fuse rating.

When I hear the words "My Son" and "Bass Test" in the same sentence seems to make my skin crawl! :D
 
It seems that all AGC series fuses are fast-acting. If you haven't done so already, check the four fuses on the inside and see if they are blown.
 
AGC should be a fast-acting fuse. MDL would be the slow blow type. If you search for AGC on legitimate sites, you should see just fast blow types. If you searched for 3AG, you would get both fast and slow blow types, as 3AG is a size of fuse. For example, the 3AG Bel fuse listed in the manual is for 4 amp version, so perhaps Adcom allowed some trade off of fast-slow and the ampere rating.

If you want to go with what you had, look at the fuse that failed, and there should be the model engraved into one of the end caps. It can be very faint, but should be readable with good light and the right magnification.

Edit: Sorry, the Bel 3AG 4A fuse was listed in the parts list part of the service manual, but the owne's manual shows as 3AG 6A. The end of the service manual has more detail, and shows the 4A one is for use on a 220V unit only. If you stick with the specific fuses listed (designation AND manufacturer) that you saw in the owners manual, you should be ok.
 
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That amp takes a 4A 250V fuse. I have the original/mk1 GFA-545 and I use slo-blow fuses (endcaps are marked T4AL250V, had to pull out a loupe to read that :eek:). I believe I saw that advice here on AK when I got the amp a few years ago, to replace the glass 4A fast blow fuses with slo-blows. When I had the amp rebuilt last year, the technician mentioned that these fuses were a good idea as well - he didn't replace them.

Edit - whoops just saw that the input fuse blew, my post is about the internal fuses on the boards. I would replace the back panel fuse with whatever you pull out; good advice in previous post that the replacement could blow as well if your son cooked something inside the amp (hopefully not).
 
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If the fuse is blackened, in my 40 some odd years of doing this, it almost always points to a defective output device. Pretty easy to check them first.
 
Also, if this is an Adcom, might want to power it up without speakers and check offset before hooking it back up. Some of them have no protection circuits so the right failure can rail your speakers, not good!
 
Thanks all very much for the responses. Yes, I cringed too. The fuse is definitely blackened. I ordered some fast acting Bussman fuses. I'll check the output devices. I could handle repairing one or more of those, but after watching some repair videos, I realized I'm not equipped nor do I have the time to do much beyond that. I may just send it off for repair. Any recommendations if I do?
 
Welcome to AK!
One step at a time.
Luxxy said:
My son blew my ADCOM GFA 545-II doing a "bass test".
Click to expand...

Recommendation? Ya.. tell son (at any age) don't touch it again or I'll do bass test in your wallet or your butt. Butt lol.. could be a teaching moment... :D
 
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