Saved a Model 11 III from the dump but......

[viennadad]

Was at a local office store the other day. They accept electronics for recycling. As I was leaving I saw a fellow walking in with a cartful of various devices. On the bottom was a BIG brown case. I asked if I could take a look. I pulled it out and its a Model 11 series III. I asked if it turned on and he says yes, at least the last time he used it. I asked if he cared if I took it versus recycling it, and he said as long as it was out of his house his wife would be happy. Took it home and yes it powered on. Hooked it up to test function and of course there's scratching when knobs are operated. The one larger issue is that the left channel was weak in stereo mode across all inputs. But, the channels balanced out when I pushed the mono button on. Any ideas on what could be a possible cause? Also, while I am waiting for the deoxit to dry, I would like to check and adjust the bias. But I have not done that before and am not sure where exactly where the leads from my meter should be placed. Any advice would help. Thanks.

 

[SoCal Sam]

Tech in the can should solve most of those symptoms. Bigger worry is DC offset which can be measured at the speaker binders. Bias is important but if amp is not in thermal runaway, you are ok for now. BTW, nice save. You will by now have noticed the empty box syndrome. Great for Seventies wide boys and fat fingered repairmen.

 

[viennadad]

Thanks. Deoxit fixed the weak channel. Understand the relation of bias to heat. Right now I am just running a pair of EPI's at no more than 3 on the volume knob. Nowhere close to pushing it. Plus the case is off in a chilly basement so there is not too much heat being generated. Better test will come later when I connect a pair of KEF's to it. For now I will check the offset, but I gather that if it is substantially off there are cap issues somewhere. Correct?