amplifier oscillation
I was having a tough time trying to find a cap to tack in. The schematic calls for 47uf,550Vdc electrolytic, I can't find a snap in cap in 550V so I made one out of 2 series 47uf, 450V caps with a resistor in parallel with each cap to balance the voltage. It cleared up the immediate problem that I was having with the presence knob. I haven't put it thru it's paces yet with getting everything heated up yet but it's sounding better than it ever has. Thanks for the help, I'm going to put it get it HOT this weekend and report back.
I was having a tough time trying to find a cap to tack in. The schematic calls for 47uf,550Vdc electrolytic, I can't find a snap in cap in 550V so I made one out of 2 series 47uf, 450V caps with a resistor in parallel with each cap to balance the voltage. It cleared up the immediate problem that I was having with the presence knob. I haven't put it thru it's paces yet with getting everything heated up yet but it's sounding better than it ever has. Thanks for the help, I'm going to put it get it HOT this weekend and report back.
amplifier oscillation
Sorry it's taken me so long to get back to this...work has been cutting into my free time...
After changing out the 47uf 550Vdc cap, I thought I had fixed my problems but I was mistaken. The high frequency oscillation is no longer the problem, the low frequency oscillation is now the problem. If the presence knob is between 8-10 and the volume is high enough I get a 40Vpk oscillation at around 120 Hz. The oscillation can be stopped by turning the presence knob down. I looked on all the electrolytic caps and the I can see ripple on only C112, it is about 10v peak. The low frequency oscillation is very sinusoidal on the positive half, the negative half is relatively sinusoidal except the first part of the negative half is linear and then rounds at the negative peak. From there it looks sinusoidal.
Any suggestions are appreciated.
Thanks
Sorry it's taken me so long to get back to this...work has been cutting into my free time...
After changing out the 47uf 550Vdc cap, I thought I had fixed my problems but I was mistaken. The high frequency oscillation is no longer the problem, the low frequency oscillation is now the problem. If the presence knob is between 8-10 and the volume is high enough I get a 40Vpk oscillation at around 120 Hz. The oscillation can be stopped by turning the presence knob down. I looked on all the electrolytic caps and the I can see ripple on only C112, it is about 10v peak. The low frequency oscillation is very sinusoidal on the positive half, the negative half is relatively sinusoidal except the first part of the negative half is linear and then rounds at the negative peak. From there it looks sinusoidal.
Any suggestions are appreciated.
Thanks
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