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Old 16th February 2017, 03:52 PM   #1
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Default F5 issue, volume ramping down and up

Several months ago, I got an F5, built with correct boards and parts, from a builder that had completed his F5 Turbo. A few days ago, the volume ramped down to a lower level while listening, than returned to previous volume after 20 seconds or so. Seemed to happen in both channels at the same time, so I'm thinking it's a power supply issue. This happened several times over several days, and I figured I shouldn't torture it any more. I do not listen at high volume, and the amp has never been more than warm when I check. A Museatex mosfet amp is now back into my system - it's a nice amp, but not up to the sound quality of the F5.

I am not technically savvy, and a multimeter is my only piece of test equipment.

Pretty sure I can get a local, qualified repair tech to deal with this. Does anyone have any advice that I can relay to him? How 'bout a link to a schematic and board layouts to help him?
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Old 16th February 2017, 04:22 PM   #2
rayma is offline rayma  United States
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Originally Posted by goofytwoshoes View Post
Pretty sure I can get a local, qualified repair tech to deal with this. Does anyone have any advice
that I can relay to him? How 'bout a link to a schematic and board layouts to help him?
There's a chance it's from an upstream component like the preamp, so try running it from a different one first.
It could be a bad power supply connection in the amp, though.
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Last edited by rayma; 16th February 2017 at 04:27 PM.
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Old 16th February 2017, 04:54 PM   #3
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Originally Posted by rayma View Post
It could be a bad power supply connection in the amp, though.
Thanks! The seller did say he'd put quick-connectors between power supply and the amp boards, so he could switch between Aleph J boards (which I also have) and F5 boards. I'll have a look. Will also change power cords, just in case.

The volume issue happened playing my turntable, and also playing music from my PC/DAC. And, with the Museatex amp in the system, there's been no issue. I have a spare preamp (Nikko Beta 30), so will give it a try with the F5.
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Old 16th February 2017, 04:58 PM   #4
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Check the connections between the pre amp and main amp. Not likely to be the main power supply.
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