Question about JVC AV-28-BD-5-Bl 28" TV
Intermittent power.No high voltage at all. All power control are working,B+ 116V ok Hor.Vcc 9V at TDA8659an ok.All Voltage at the secondary chopper seems working very well,except the output of hor out at pin#39 of TDA8659AN is not oscillating at all.But sometimes the TV will work fine, even for 24hrs continuous used,but if u turn the TV off for about 6hrs,the next time you turn it on again no power again.Keep on pushing the power button on/off the TV will work again. My finding's is something is triggering at x-ray protect pin#52 TDA8659an to cut-off the hor out oscillation at pin#39 of TDA8659AN.Until now I can't get the real culprit. Your assistance is very appreciated.
Try checking the filter in the 116v line. You may have an intermittent spike coming through the B+ line.(The filter may have decreased in value) Also a small filter in the X-ray circuit could have lost capacitance. There is a low value capacitor (about .047uf @400v) in the collector circuit of the horizontal output transistor that will detune the horizontal circuit causing the HV to go too high. If this cap is intermittent it may be causing your problem. Stargazer Hope this helps
Posted on Sep 02, 2007
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