Re: Tektronix 2246 flickering screen, ch2 not working.


grusus@...
 

After taking some break in troubleshooting this scope, I got back to it.

After analysing service manual I got to the point that sth is messed up with clock/timing.

I think this is corelated with visible retrace.

Checked clock signal around U2409, U2508, U2507 - all seems fine. I am little concern about timer reset signal (+1VDC, no ac - only 8Mhz ripple from main clock - I don't know how it should look like), and INTR signal - also only dc no ac.

Today I made small experiment and dissconnected RO BLANK (R2419). Readouts are much brighter, grid dot is fully present, readouts are less blurry and more stable.
On Video I am connecting and dissconneting R2419.

https://photos.app.goo.gl/341Lxitp8DYbE9R97

That is why I am almost certain that there is some timing/interrupt/clock issue in this scope. It blanks when it shouldn't,

Can anybody give a hint what to check next? How to address this problem?

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