Adcom GFA555-II help needed...
Analogman
Posts: 1
I recently picked up an Adcom GFA555-II at a local yard sale in excellent physical condition, but only the right channel works correctly. I checked the fuses, and all are good and the correct rating for the channel rails at 7 amps. It does not blow any fuses on power up or during use and seems to have correct rail voltage 80v/-80v.
I do get a minimal but distorted signal from the left channel with the volume on my preamp turned up beyond normal listening levels. The only damaged (burned out) component I found was a resistor (R-107) 3.9k on the input board which I replaced?no left channel improvement. Everything inside looks original, all Toshiba labeled outputs. The bias on the right channel is 10.5mV and stable; there is no reading on the left channel.
Where do I start looking for the problem?
Thanks all?I really appreciate your helping me to get this fixed.
Service manual link---http://akdatabase.org/AKview/albums/...%20Service.pdf
I do get a minimal but distorted signal from the left channel with the volume on my preamp turned up beyond normal listening levels. The only damaged (burned out) component I found was a resistor (R-107) 3.9k on the input board which I replaced?no left channel improvement. Everything inside looks original, all Toshiba labeled outputs. The bias on the right channel is 10.5mV and stable; there is no reading on the left channel.
Where do I start looking for the problem?
Thanks all?I really appreciate your helping me to get this fixed.
Service manual link---http://akdatabase.org/AKview/albums/...%20Service.pdf
Post edited by Analogman on
Comments
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i bought an Adcom GFA-7500 that had the same problem. It was a filter cap that was going bad. The tech said that one way a filter cap can go bad is if the power amp has not been under load for an extended period of time. The one i got had not been used in a couple years so that could have been the problem. He also said that filter caps can become fatigued depending on the amount of use of the unit, but as a general rule it is not a bad idea to have them replaced every 10 years anyway. I cost me about 150.00 to do all 5 channels, but it became essentially new at that point. Depending on where you live i know of a couple of great Adcom repairmen. One is in Nashville, and the other is in Milwaukee I think. Just PM me and I will get you their contact info if needed. Good Luck!Living Room: HK AVR 354 as pre/pro, 2 x Polk Audio Micropro 4000, Adcom GFA-7500, 2 x Mirage OMD-15
2 x Mirage OMD-5, 1 x Mirage OMD-C1, APC H15, Sony S790, Philips 52" LCD, Beogram 3000, FAT (Firestone Audio Tobby DAC), Harmony One
Den: Sherwood R-972,as pre/pro, 2 x Velodyne SPL-1000R, 3 x Crown Drivecore XLS1500, 2 x Polk Audio Lsi9
1 x Polk Audio Lsic, 2 x Polk Audio Lsifx, Sony S790, APC H15, Dspeaker Dual Core 2.0, W4S DAC 2, Keces DA-151 -
Another great site for help is Audiokarma. There are many knowledgeable people there. Also try a google search with your problem.
