Hi!
I have this DMC-80 on the bench with a hum problem. I usually only do hifi gear but as I know the person I wanted to give it a try. The filter caps were in pretty bad shape so I replaced them but as the hum is 50Hz this didn't fix it. When I plug something in the line in the hum disappears so I'm thinking it's in the drive/tone stage. Turning up the volume does increase the hum somewhat. I did check for cold solder joints but didn't find any, removing safety ground (just for testing) doesn't improve things either.
I have this DMC-80 on the bench with a hum problem. I usually only do hifi gear but as I know the person I wanted to give it a try. The filter caps were in pretty bad shape so I replaced them but as the hum is 50Hz this didn't fix it. When I plug something in the line in the hum disappears so I'm thinking it's in the drive/tone stage. Turning up the volume does increase the hum somewhat. I did check for cold solder joints but didn't find any, removing safety ground (just for testing) doesn't improve things either.
Attachments
Thus the amp is innocent. More probably, a shielded cable broken, or entering though the guitar pickups.
I have a doubth: what kind of lights are using in the place that the amp and guitar are? Modern led and fluoro have a RF generator to convert AC into an RF to light fluoros (compact) or a switching buck converter (led) that usually are very bad filtered or no line filter at all. Then wiring act as aerials or antennas spraying lots of RF signals. Still worse if there are more than one, because there may be heterodynes between all them creating more much RF on the site.
Led lights are a filth. Almost here in Argentina where regulation agencies are inexistent, the lowest quality of them are available, and as ham radio, I insult in all languages: they spray large quantities of RF that includes the 144 and 432 MHz ham bands. When street lights are on, to have a brief dialog with a distant friend is impossible.
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I have a doubth: what kind of lights are using in the place that the amp and guitar are? Modern led and fluoro have a RF generator to convert AC into an RF to light fluoros (compact) or a switching buck converter (led) that usually are very bad filtered or no line filter at all. Then wiring act as aerials or antennas spraying lots of RF signals. Still worse if there are more than one, because there may be heterodynes between all them creating more much RF on the site.
Led lights are a filth. Almost here in Argentina where regulation agencies are inexistent, the lowest quality of them are available, and as ham radio, I insult in all languages: they spray large quantities of RF that includes the 144 and 432 MHz ham bands. When street lights are on, to have a brief dialog with a distant friend is impossible.
🤬Actually no the amp is not innocent as shorting the input doesn't reduce the hum. Also the hum is the same whether something is plugged in or not. The only way to reduce the hum is to plug a jack into the "line in" which separates the tone and drive stages from the power amp stage on the dmc-80. I thought about interference and turned off everything else in the room including lights but that didn't improve thing either.