Re: A 2465 teaser...

Chuck Harris

U400 was high on my list. Its pins have all been given a drop
of deOxit, a second U400 was tried, and the suspect U400 was
tried in the working scope.

I checked the bias resistor, when the hybrid was out, and it measured
correctly, it had continuity to its supply. I checked the HF response
5K pot, it is good, and was adjusted to near full value... which means
the scope would have been a good candidate for the 1K -> 4.3K series
resistor change that happened at later serial numbers.

But, I agree, it would be worth looking at supply and bias connections
a little more carefully.. probably doing something like drawing current
from them to smoke out bad solder joints, etc... that might not be seen
with a low current ohmmeter.

-Chuck Harris

very_fuzzy_logic@... [TekScopes] wrote:

A fault on Ch1, Ch2 but not Ch3, Ch4 or vice versa makes U400 the obvious culprit but you have checked most possibilities. It might be a long shot but incorrect bias current into U400 would probably change its switching speeds and it's worth checking the bias resistor. Also clean the contacts in U400's socket?


Join to automatically receive all group messages.