Hello, I have just purchased a SAE A502 power amp, runs great, however when in idle position, over time, the right channel becomes warm to the touch without a signal. The left maintains cool temperature, and both channels when driven appear to be stable, however the right channel stays relatively warm. Could this be a bias problem, a pot adjustment perhaps, or a component that may be fading, welcome any responses. I don't have a service manual, however have just downloaded a schematic for the amp. I am glad to be a member of diyAudio, thanks.
for A 502 bias circuit can be rather tricky since there is no adjustment ....one trimmer that exists there is only used to play with ofset
first verify what idle is running on the "good " amplifier cause this also might be wrong or too low ...then check with the "bad" amplifier to see where the diference lay and why
to my understanding i give more than 50% that this is some mechanical error and not electronic ....a number of devices that need to be firmly attached on heatsink might be the cause
often amplifiers like that have both capacitors and soldering issues ...look at that too very carefully
( one of the things i find wrong in other wise perfect amplifier is the placement of the power caps )
let use not forget that this is an old machine that needs to be looked at carefully
schematic is available if you like to have it e mail me
( hello Jan my friend ... !! how are you ??)
first verify what idle is running on the "good " amplifier cause this also might be wrong or too low ...then check with the "bad" amplifier to see where the diference lay and why
to my understanding i give more than 50% that this is some mechanical error and not electronic ....a number of devices that need to be firmly attached on heatsink might be the cause
often amplifiers like that have both capacitors and soldering issues ...look at that too very carefully
( one of the things i find wrong in other wise perfect amplifier is the placement of the power caps )
let use not forget that this is an old machine that needs to be looked at carefully
schematic is available if you like to have it e mail me
( hello Jan my friend ... !! how are you ??)
Hello Jan and Sakis, wow, thanks for the prompt reply, just came up for air with family July 4th activities, boss (wife) has me booked solid and upside down today. Thanks so much for the information about the schematic, I think my next step will be to begin slow disassembly process from the case and begin examining the inner construction of the amp. The amp was just shipped via ground UPS, so may have jostled some of the inner components; I agree that it just may be something as simple as a mechanical error, one will hope this is the case. Good thinking about determining the good channel as actually good, and just thinking, since I am totally unfamiliar with this amp as well as the actual SAE name, does this amp naturally run warm............Is there a chance that a service manual is available, as this will help with running some technical checks? Well, the boss is calling, must dash quickly, can't wait to get started on the amp, thanks again for the fast response, and all have a wonderful and safe 4th of July!!!
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