Sherwood XA-1240Q

I have this Sherwood amp I am trying to get going again. Problems are channels 3 and 4 work fine, channel 1 has no sound, and channel 2 has sound, but it has static and cuts out. This amp is also fan cooled, which if I remember right, the fan was always on. But one this amp the fan is off, no matter what the amp does.

So far, rail voltages are +29.9 volts and -27.7 volts. Nothing looks bad, may have found a bad Zener D560, which reads .757 one way and 1.87 the other way (on diode check), (this is for the cooling fan). I do have a schematic for the amp if needed.

Any ideas???

Perry Babin

Paid Member
2003-11-20 11:01 am
If it spins freely with no power applied, the fan may have a defective drive component. If it doesn't spin freely, the lubrication in the bushing may have dried up. In most fans, you can remove the old lubricant and the fan will work normally. A drop of motor oil will generally be a good lubricant (after the old lubricant is removed completely) if the bushing isn't worn too badly.

When you begin on the audio problem, you'll need to follow the signal from the point where the RCAs solder into the board until you find the point where the audio stops or becomes noisy. I'll assume that you've already operated all of the switches and pots through their entire range to confirm that none are intermittent.