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BFDR Parasitic Oscillation

12/31/1999 5:17 AM
Matt	BFDR Parasitic Oscillation Hi Guys, Have a '67 BFDR which has a parasitic oscillation problem on the vibrato channel. The output power is real low and sure enough on the scope, there is a large high frequency component on the 1000 Hz signal being injected into the amp. If I place a .001 cap across the wiper and ungrounded side of the tremolo Intensity control, the power is back to normal and the signal quite clean. I don't want to rob the amp of frequency response and I thought it was only silverface amps that suffered from conditions that made them susceptible to oscillation. Has anyone experienced this? Is there a way to improve it without resorting to suppressor caps? I've resoldered joints, tried to move wires away from each other, kept signal wires near chassis, changed tubes, even Deoxit'd the tube sockets. My last amp was a totally different situation with a faulty vibrato roach. This one isn't so easy Thanks a million! Matt

12/31/1999 5:17 AM

Matt

BFDR Parasitic Oscillation

Hi Guys,

Have a '67 BFDR which has a parasitic oscillation problem on the vibrato channel. The output power is real low and sure enough on the scope, there is a large high frequency component on the 1000 Hz signal being injected into the amp. If I place a .001 cap across the wiper and ungrounded side of the tremolo Intensity control, the power is back to normal and the signal quite clean. I don't want to rob the amp of frequency response and I thought it was only silverface amps that suffered from conditions that made them susceptible to oscillation.

Has anyone experienced this? Is there a way to improve it without resorting to suppressor caps? I've resoldered joints, tried to move wires away from each other, kept signal wires near chassis, changed tubes, even Deoxit'd the tube sockets. My last amp was a totally different situation with a faulty vibrato roach. This one isn't so easy :-(

Thanks a million!
Matt

Replies:

SpeedRacer In no particular order..1. ... -- 12/31/1999 7:49 PM
Tracy MattThe parascitic ... -- 1/2/2000 8:12 AM