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  #1  
Old 07-27-2013, 10:37 PM
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radiotvnut radiotvnut is offline
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'77 RCA 12" B&W KCS203D chassis

A friend picked this up at a flea market for next to nothing and gave it to me. This is a 12" solid state RCA B&W TV from '77 and the interesting thing about this TV is that a modified version of this set was supplied with earlier models of Rasio Shack TRS-80 computers. I recall the monitor version not having a tuner or speaker and there was a cover plate over where the tuner would normally be found. The video cable ran through the hole where the volume control would be on the regular version. I actually saw the monitor version at a yard sale a few years ago; but, I didn't buy it.

This set had a very weak CRT; but, I was able to rejuvenate it. However, the picture is still very dark and the CRT socket voltages seem to check very close to what they should be. I'm still concerned that the CRT may be at fault because after rejuvenation, the meter pegs on the emission test. When the set is first turned on, the brightness will sometimes fluctuate for a few seconds and I can sometimes turn down the contrast to briefly get a brighter picture and retrace lines.

I really don't have time to mess with it now; but, I think I have a known good CRT that came out of a similar RCA TV from the same time period.



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Old 07-29-2013, 09:17 PM
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vinljnkie vinljnkie is offline
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I googled 12vbnp4 and found Video Display Corp has new ones for sale for $35 if the one you have isn't correct.

http://vdc.mybisi.com/product/12vbnp4
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Old 07-30-2013, 07:33 AM
zeno zeno is offline
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Sounds like you may have shorted the jug shooting it.
Try tapping the neck while its on, it may prove it.
Also a "remove short" may work if your tester has it.

73 Zeno
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Old 07-30-2013, 03:13 PM
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radiotvnut radiotvnut is offline
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I retested the tube and it showed a brief G1/K short that went away after I tapped on the neck. However, the emission reading was still pegging the meter; so, I flipped the tester to "clean and balance" for a second and then flipped it back to "remove shorts" and pressed the button. I saw a flash in the neck, with the emission reads about 1/4 into the good scale and the cut-off control having to be lowered to achieve proper cut-off. It now has a watchable picture; but, it's still not quite bright enough. I'm going to get a diagram and test the CRT voltages.
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Old 07-30-2013, 11:33 PM
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Even though the tube tested reasonably well at first, I tested it later and the emission had fallen into the lower end of the good range. I replaced the tube with the spare I had on hand and the picture is not plenty bright enough. I suspect the old tube was probably gassy.
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