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Hello,
I am working on a friend's Valveking 100 which is experiencing an interesting issue. After playing the amp for a period time (some times as short as five minutes, other times closer to an hour) the volume ramps down in a similar manner as to when the standby switch is thrown. Usually within a few minutes the volume will increase again back to normal levels.
I could not manage to recreate this behavior on the bench. Reading tales of leaky muting FETs, I replaced them both out as a precaution. I also touched up some sketchy solder, brought it up slowly, and stress tested it for an hour with no issue. It was not until today that I witnessed the amplifier exhibit said behavior when he called me to his residence. I quickly jumpered the effects loop to make sure that was not the issue. No dice. I plugged directly into the return and it exhibited the same problem. I then plugged the send to a secondary amp and the problem persisted.
If I am counting my cards right, I would assume at this point we have to be looking at a power supply issue. The intermittent and unpredictable nature of it is making for some difficult troubleshooting. I am hoping that perhaps some of you helpful folks might have experience with this line of amplifiers and some insight into what is occurring.
Thanks in advance!
Chris
I am working on a friend's Valveking 100 which is experiencing an interesting issue. After playing the amp for a period time (some times as short as five minutes, other times closer to an hour) the volume ramps down in a similar manner as to when the standby switch is thrown. Usually within a few minutes the volume will increase again back to normal levels.
I could not manage to recreate this behavior on the bench. Reading tales of leaky muting FETs, I replaced them both out as a precaution. I also touched up some sketchy solder, brought it up slowly, and stress tested it for an hour with no issue. It was not until today that I witnessed the amplifier exhibit said behavior when he called me to his residence. I quickly jumpered the effects loop to make sure that was not the issue. No dice. I plugged directly into the return and it exhibited the same problem. I then plugged the send to a secondary amp and the problem persisted.
If I am counting my cards right, I would assume at this point we have to be looking at a power supply issue. The intermittent and unpredictable nature of it is making for some difficult troubleshooting. I am hoping that perhaps some of you helpful folks might have experience with this line of amplifiers and some insight into what is occurring.
Thanks in advance!
Chris
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