Got one that chirps the same way, flex the A 18 board corner and normal operation resumes.
Flex/relax problem repeats, start trying to narrow it down, 1 amp fuse blows, remove A 18 board, test and find gate-source leakage in Q 933 and crow bar fires when AC voltage in is raised above 60.
Checking T 933 winding 9,10, the one that is negative line bridge rectifier (pseudo ground) tied to one side and earth ground through C 932.
That resistance measures 0.4 ohms, whereas the similar (in wire gauge) 6, 7 winding shows 2.2 ohms.
The winding is not used as the grounded shield is installed and there is no C 932 installed.
I have other 2215's and will check that winding resistance on at least one.
If it turns out to be shorted, I have two options, since all tektronix 120-1439-00 seem to have been exhausted:
1) dis-assemble, count turns, measure wire gauge, rewind, eliminating the 9, 10 open circuit winding as not needed.
2) got two of these cheap, NEW MAGNETEK TRIAD TRANSFORMER F-40X 115V VOLT 26.8V.C.T@1A AMP,
Wire the 120 VAC in parallel fed by P1, P2 to A18 one full secondary plus the second to the center tap to
fast-on 1, 2 on the A 18 board, a 10 ohm resistor or choke (AC Power Choke, ( D-37-N) 0,6 H 0,51 А, made in USSR , NOS. Lot 1pcs) between T 933, 1 and Q 933, D.
Already checked the scope with a 40 volt bench supply for several days.
I would leave the crow bar circuit and 1 amp fuse to blow if the supply goes over-voltage.
this arrangement can also have the primaries wired in series for 240 volt operation.
Internally mounted, this would add about 4 pounds to the weight, but nowhere near the 12 pound weight of the Sorensen 40-0.75 supply, not to mention only a single lift.
Anyone with T 933 winding turn-count /wire gauge would be greatly appreciated.
Keep the old dogs running!