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Spec 4 with Problems

To answer a previous question, no there are no fans or other HVAC ductwork in my work area, just the ambient air, so air flow shouldn't be an issue.

The good amplifier was very steady after an hour and varied between 3 and 5 mv. I did use a straw and blew on Q1 thru Q5 and D1. Although Q1 had the cover on that I mentioned earlier, when I blew on it, the mv went up to 26 from 5 almost immediately. After I stopped, it slowly went back down to the 5mv.

Blowing on the other transistors or D1 had no effect. Q1 is very sensitive.

I'll try the same later on the drifting amp and post the results. I did put some heavy shrink tube on Q1 to mimmick the factory cover as Warren suggested.
 
With the shrink tubing on Q1 and the bottom and top case plates attached the amps are fairly steady. They drift about 10mv.

When I blow on Q1, there is immediate drift on any of the amps I have (3 working).

I think its good enough now to call it acceptable. The unit works and all the other problems have been solved. I'm just accustomed to my SX 1250 which has no drift.

Thanks for all the help to get me to this point.

Now for the next challenge under a separate thread, getting the 4th Amp to work. It was missing the power outputs, another transistor and several of the resistors were burnt.
 
Here's a picture of the Cover over Q1. Q1 is in the bottom center of the picture with the tan cover on it.
 
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