I've read several reports of this happening to this amp.Īttached are schematics showing as built, and then with a 100K 'fail safe' resistor added. Without this resistor, if the wiper goes open, the output tube red plates and all sorts of bad things happen. This can easily happen if some dust or dirt ends up inside it, corrosion or it simply fails. The design of the output tube bias boards leaves out an important component, a 'fail safe' or 'emergency pull down' resistor in case the wiper on the potentiometer goes open. Of all the things I have seen about mods for this amp, the issue in this post is an important one for reliability and safety!
