Looking for some help with Adcom gfa-5503 - diyAudio
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Old 26th April 2013, 12:10 AM   #1
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Question Looking for some help with Adcom gfa-5503

So I just bought an adcom 5503 amplifier. It does work and sound ok but it runs very hot even while on very low levels. Also there is a horrible buzz sound coming from the toroidal power supply.
First off ill tell you about the temps. All 3 channels are within 5 degrees F of 125. Now it does take a few hours to get that hot but it still does. I started with a cold amp the other day and played music at a pretty decent volume and it didn't get that hot, so it is something that is taking a while to do. From what I have read its probably a slightly high bias maybe?
Now about the buzzing toroid. It is a pretty decent buzz coming from the front of the amp. It is affected by turning on my av receiver. As in it will get loud then go back down when I hit the power. I tried a 3 to 2 prong adapter to rule out ground issues and it made no difference. Also there is a hiss in my tweeters that sounds just like the buzz.
Another thing that I noticed was that the power light doesn't stay on long after the power is turned off. I have a 555 Adcom that the power light will stay light for like 30 seconds before going out. The 5503 might stay on for 3-4 seconds. Could this mean there is a bad capacitor? And maybe it is causing the toroid to buzz? Just a thought.
I did measure the dc offset and the L/C/R measures 9.4/14.4/27 mv. My plans were to tear it down and look over the components for obvious damage, bad solder joints and maybe take the big capacitors out and take them to be tested. I will clean everything up and set the bias and dc offset and see what the result is. Is there a way to test the toroidal transformer? Or if I took it with the caps maybe a shop could test it? Any ideas what's going on here? Any help would be appreciated. Thanks mike.
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Old 26th April 2013, 11:42 PM   #2
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Does this look like a replacement part or original? Can't come up with anything online?
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Old 26th April 2013, 11:46 PM   #3
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Here is a close up of the part numbers. Anyone know if this is a good replacement?
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Old 27th April 2013, 10:50 PM   #4
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Ok so the transformer is an original adcom there's a sticker on the bottom of it. But however I took the amplifier boards off to inspect them to find some very bad solder joints and a loose resistor. I will go through and freshen up the solder joints. Here is a pic of the findings. I did measure the resistors and most were right on, a few we're not probably due to it being in circuit measurements. Also I see that the adjustment pots were replaced as there are two boards with grey ones and one board with blue ones.What is a safe way to clean the boards off without taking any components off. Is there anything to watch out for? I appreciate any help with this project. Thanks mike
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Old 6th June 2013, 06:50 PM   #5
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Location: Colorado
To clean the boards I would recommend Deoxit by caig labratories.
CAIG DeoxIT D5S-6 Spray 5 oz. 341-200
I owned a repair shop that also perfomred fire and water damage restoration for several years. That was my big secret instead of subjecting electronics to ultrasonic baths. It washes dust, carbon and soot off like magic and seals the surface to prevent further oxidation. It works great and it's not very expensive. Simply spray it on the boards, and the dry off with compressed air. If you have a compressor, make sure you have a water filter in line.
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