Hi everyone, I have a Tektronix 7B85 delaying time base in need of repair.
Everything else works fine except the trigger. The problem is 100% A2 trigger board assembly as I have a working 7B80 that I switched boards with, and the trigger worked fine on the 7B85 with the known good A2 board.
Anyway, here are the voltages I got from the test points from the manual.
The format is as follows: "reference designator"-"pin number", "actual voltage", "(expected voltage)"
All readings are in volts unless specified otherwise.
U65-5, -3.77, -4.93
U65-4, -0.726, -0.68
U65-2, -0.05, -0.05
U65-8, -2.05, -2.44
U65-6&7, -2.05, -2.5
U65-10, 0.309, 0.02
U65-3, 0.743, -0.12
U65-1, 3.50, 2.98
_________________
U55-3, 3.42, 3.51
U75-5, 3.81, 3.56
U75-3, 3.80, 3.50
________________
U85-13, 1.072, 3.88
U85-14, 1.037, 3.86
________________
All voltage rails are reasonably okay.
Unsure if U65 is the problem. The voltages change when a known good IC is used instead, but the suspect IC works in the working 7B80...