Quote:
Originally Posted by cluelessgame
will do, just curious tho, what makes you think that?
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Second that, losing half the screen horz would tend to indicate a problem that is blanking at the horz rate. Most BW sets do not even have horz blanking (well older sets anyway) the just rely on the sync pulse to cut off the CRT. this is where a scope would come in handy as you could examine the signals at the CRT to see where the defect is. I am sure its the pin 3.
would like to add that I would replace all the caps in the boost filter supply, and also check resistors and replace caps in the horz blanking.
As too why the spot, that's a tough one. fix the blanking then try running it for an extended time (like 10 min) see if turning it off then still gives the dot.
I have a set that if I turn it on for just a short time (like right after the raster comes up) then turn off the spot is there, very bright very long. But if I watch for any length of time its not a issue.
I recall reading somewhere that a weak tube can do this as well but not sure about that, I do have a tube (27ZP4) that did this. it was weak takes a few min to come up to decent brightness. The spot bothered me on that one so much I made up a little cap/diode/bleeder resistor in the brightness circuit that would cut off the tube by discharging the cap into the cathode with a pos voltage when the set was turned off (think that was it, its been a while).