Quote:
Originally Posted by FERNSEH
A small amount of DC component will be introduced into the frame scanning coils which will cause a degree of picture shift. Also, because the resistors R92 & R93 are inserted before the main smoothing capacitor a tiny amount of 50Hz ripple will be present in the scanning coils. Why would the designer want to do that?
DFWB.
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I was rather hoping you were going to tell me the answer
I can't see why you would want to introduce a DC component to the scan coils for picture shifting- after all there are magnets for that. Could it be some attempt to compensate for variations in picture size as the HT voltage varied? Or some sort of 'anti breathing' device to counteract the effects of mains hum in the frame timebase? That was the best I could come up with, although I'm not sure how either would actually work.
They must have thought it was a good idea as they used it in several chassis.
Anyway, the whole thing is now reduced to a 'PT650 self assembly kit'
The next task will be to remove the remaining components from the frame timebase panel and the speaker panel so that these, along with the bottom panel can be sand blasted, prior to either re- plating or painting.
Cheers Nick