motorola ts4d 7 inch

[timmy]

finishing up on another motorola table top tv with the 7jp4 crt and i have 3 crts 2 are bearly able to show a pic but they do and the brightness turned down the screen goes black and thats normal but i have the other crt and is brighter still not the best but the brightness turned down dont shut the screen down its as if the pot is bad or the b+ was taken away. my other set brightness shut this tube off but for some reason just this tube wont shut down but the other 2 will. any ideas why that is ?

[compucat]

Possible heater to cathode leakage or short? A heater to cathode short will cause the brightness control to have little to no effect but usually in such a case the picture will be washed out or have retrace lines that cannot be removed. I wish someone could manufacture a replacement CRT for these sets. It is essentially a scope tube so it shouldn't be that difficult or costly.

[timmy]

its odd since the other set i redone i used this crt and brightness worked fine but taking it out of the closet and useing it on this set im doing now the brightness dont turn it off. is it at all possible that it developed a short from being put away since the last time i used it.

[timmy]

well i didnt think it was all that possible for a crt stored in a closet would develope a heater cathode short from sitting idle. so i took another look at the chassis im working on and there is a resistor off the bright pot that in early models have a 1 meg resistor and newer models have 500k or a .470meg but mine appears to have a factory mistake having a 2.2 meg resistor in place and the solder looks factory. i guess if no one ever turned the bright down no one would have ever known the wrong resistor was in there. so after changing the resistor to a 500k the bright works fine now and no lines across the image. bright up full does give the lines so i made the change for retrace and, no more lines. so the 7jp4 that i thought was bad is not, its good,lol.