Thank you for your reply Mark,
I have disassembled the entire 177 and checked all the wafers one by one but could not find anything wrong.
The 177 was not meant to be taken apart for cleaning, I can assure you, but I have managed to do that!!!
I used a fine sandpaper to clean every contact of the rotary switch.
After reassembling the resistance readings were as before, but I was able to perform the calibration according to the 177 manual, but I could do that before, so I think that I may be barking at the wrong tree.
So I decide to leave the 177 as it is for now and focused on the "main problem" again, which is:
What is causing the "dot" move down the screen when I flip the 177 switch to R in step 9c of the Vertical Gain Adjustment (of the 577).
It should move up and I should use its position to adjust the vertical gain pot.
My current concern is Step Generator circuit (fig2).
It can produce current and voltage steps but the voltages around Q330, Q324, U220 etc are way off and do not change as expected when I change from REP to SINGLE.
The transistors tested ok with a "digital transistor tester".
I will probably open another thread once I have studied the problem deeper.
Regards,
Roger
