Quote:
Originally Posted by beery
just for reference I have attatched part of the circuit of the Ekco TMB272 which is very similar, but I notice here the diode is properly biased.
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Interesting, only one stage of integration (that is still ok but in theory the H serrations are better filtered off with a two stage filter) and a very short time constant of about 24uS (RCA recommended 50uS). This will result in a very fast rising high amplitude V sync pulse though. Probably one advantage of mixing in the syncs in the plate circuit, the transformer itself has LPF properties that help reduce its response at line frequencies versus vertical rate, so probably you can get away with the shorter time constant in the integrator components, than in the case where the sync is introduced directly to the grid.
(The time constant is at least 200uS, or more in the TV22, could be longer too, depending on the behavior of the diode).
Does the TMB272 have any line pairing/ interlace issues ? I would expect that it would not have any issue, unlike the TV22.
PS : I've always liked the look of the TMB272, but I was not able to get one sent here. However, some years ago there was a fellow in the UK who sold me a CRT from one and that is what I have in my TV22. Because it did not have an external aquadag, I added an EHT filter capacitor inside the EHT cage (you can see it in the photo I posted previously post #24) and made an acrylic insulator top to go over it to prevent any corona discharges.