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Post by DRZ on May 5, 2021 16:24:22 GMT -7
120 Hz hum is caused by half wave rectified DC power that has a bad filter cap. The Metro loop has a large standup filter cap right by the input power connection. I have on occasion had to touch up the two solder connections on the underside go the Metro board. Put your finger , with power off , on the top of that black stand up cap and see if it wiggles any. It should not if securely soldered. If it does wiggle remove the nuts holding the 1/4" jacks and slide the board out , flip it and with a hot soldering iron touch up the two connections for that cap. Re install jacks and test.
Z
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Post by DRZ on May 6, 2021 2:09:19 GMT -7
You're welcome Don. But please understand there is no substitute for having an amp on my bench and troubleshooting it. When asked about a certain issue all I can do is draw on my past experience and advise to the first thing I would check. I hope my advise helps as I have had similar issues with Metro E/F boards. If not a quick trip to the factory will suss it out. Z
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