Re: 2205: Channel 1 problem


UPDATE: Upon closer inspection, I have two out-of-spec voltages on U30. Also, I noticed two bodged diodes across pins 2 and 3 of U30 (and comparable U80 on Ch. 2). These are from a manual change M67537 indicating the addition of these diodes A2CR14 and A2CR64. But, on my scope they are installed backwards from the indicated manual diagram. So I removed them, checked them on a diode checker, and reinstalled as indicated in the manual. No change in Ch. 1 problem. The voltages on pins 2 and 3 are still out of spec as follows:

A2U30 pin 2 should be 0v. I measure +0.52v
A2U30 pin 3 should be -0.8v. I measure -0.28v.

The voltage difference between pins 2 and 3 is the same (0.8v) but is 0.52v high.

The +8.6 and -8.6 supply voltages around this circuit all look good.

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