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I obtained a NEC dt-4861s RPTV unit.


Heres the story, based on what I've done, learned, and read up.


I powered it on, and The HV came up, along with the amplifier, and the corner channel screen. I could change channels. There was No Raster, or no sound. None of the inputs OR ouputs worked. the power amp does work, as I injected a signal into it. So, I look at the CRTs, and they are happily glowing. there is NO raster, and there is a typical light CRT burn-in. not as bad as ive seen them before.


I pulled out the deflection/convergence board and resoldered Q401, and Q402. I resoldered a driver, and checked out the entire board for more. I tested the joints, and circuit traces for unfixed opens, and they checked out good. All of the transistors test good in the vert area. I repower it up, and I now hear a standard vert pulsing in the yokes, as I didnt before. one-step closer.


It seems as though nothing on the RF/Signal Input board is workin at all. I pulled up a datasheet, on the chroma IC, and I checked for a VCC voltege on pin5, and I got 0V!! I checked pin 24 for a 12V sorce, and got nothing. the only reading I got, was typical ground fault. I redid the grounding and went back to 0V.


Based on this, I have no source to power the board. (hmm, makes you wonder)lol . there is no video amp stages running, no sound/video IF, no jungle, no nothing working on the board.


Any Ideas or help that could lead me to the sorce of the problem?? I cant trace it back, as I have no schematics. Not sure where the board gets its power from. The power supply cable goes directly to the deflection board. so I guess it derives it somehow from that board. the tuner board in the upper screen area works, cause it controls the front panel controls, and the channel display. and they respond just fine.


I learned that fluid leaks out and ruins things, but there is no trace of leaked fluid, and the fluid is all there at proper level in the CRT. I heard the CRTS fail, but no way to test, as I have no drive signal going to the R G B xistors. (makes since).


P.S. There is a connector CA on the RF/Input board that has no cable plugged into it, and I dont see one for it.


Any help? Purtty purtty please?!? Sugar on top =(
 
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