Vox AC10 RFI Pickup [Archive] - Music Electronics Forum

rf7

03-01-2008, 03:04 AM

What would cause a guitar amp to pick up radio stations? It only does it through the normal channel, not the Vibrato channel.

Enzo

03-01-2008, 05:26 AM

Usually the loss of a good ground connection at the input jack.

rf7

03-03-2008, 12:12 AM

Thanks Enzo, for the reply. The input grounds measured OK, but someone had replaced the 3 prong AC plug with a 2 prong one. When I installed a 3 prong plug back on the AC cord, the RFI went away. The amp came stock with a 3 prong cord, according to the schematic.

rf7

03-05-2008, 11:37 PM

I spoke too soon. It turned out that adding the grounded plug stopped the RFI when nothing was plugged into the amp. So, I still had the problem whenever I had a guitar plugged in. After checking and re-doing all of the grounds, I got the problem to go away by adding grid stoppers on the preamp tubes.