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Re: I have an Adcom GFA 555 type II that won't shut off...
Hi, please replace power switch to solve amplifier problem as power switch internal contacts seems stuck and does not disengage to turn power Off. Thanks.
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Obviously you are going to use the Front pre-out's on the Sony to drive the Adcoms. its pretty straightforward, just do not use a speaker that is less than 8 ohms. and make sure that you always have the power switch off on the adcoms, let them sit off for 5 minutes, THEN hit the bridge switch on the back of the adcom's and follow their instructions for bridging. it's pretty easy and tough to go wrong. Good luck...Rob
Sorry to contact you this way but i've spoken to an older colleague of mine and it appears that before 1992 in the Adcom GFA-555 they were using bipolar transistors and the amp was rated fo a minimal impedance of 4 ohms - not like in the newer ones that have MOSFETs and are rated for 1 ohm in bridge mode. So the fast fuses that you need are of 6 amps , not 20 like in the newer models.
Sorry for my mistake.
Have it serviced. Do you know what GFA stands for. People at Adcom do have a great sense of humor. Take it only to a high end audio servicer. Contact Adcom. This is good stuff you wouldn't want a hack working on it.
Any fuse blowing is caused by a shorted component in either the power supply section or main audio amp part. Follow the fuse circuit and see where it leads you. Look around for burnt of damaged parts. Suspect anything sitting on a heat sink. The most common culprit is the audio amp main transistors, especially if someone shorted the speaker leads together. In the power part it could be the transformer, the large Electrolytic capacitors, rectifier, or voltage regulator. Some amps use an IC for amplification and this can blow the fuse.
First of all, when bridging an anp, the impenence that it can handle usually goes UP not down. I don't believe that the GPA555 can be bridged without circuit modification.
The input jacks on a 555 are a standard gold plated, high quality jack. looking around the net, you should pay no more than 7-10 dollars each ( or just get originals from Adcom. ). What is your comfort level with electronics?. Can you solder properly?. I cant answer this without more info.....thanks...Good luck...Rob
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