The customer said he smelled something burning a number of times when trying to power the set on. He says he never saw any smoke. We tried it when it came in but there was only the sound of a relay energizing and then dropping out about one second later. I could not locate visually or (with my nose) where anything seemed to have burned from. I checked the HOT and the SCR and three diodes nearby it and found them all to be good. I repaired the troublesome coil also. I can hear the little chirp from the power supply when you first plug the set in which leads me to suspect that the SMPS may be good. I have seen flybacks go bad in some of these but I don't own a ringer so I can't be certain of that. Can anyone offer a rule out or troubleshooting procedure or perhaps an opinion based on the symptoms I've described? Thanks for any assistance. Lenny Stein, Barlen Electronics
RCA TV model F32450, Ch. ATC113CA1 just clicks
Sep 30, 2005
3 Replies
HOT plus IHVT plus plus.
Have fun
kip
I scoped the collector of the HOT while attempting power on. It peaked at only around 600V and looked pretty bad. After replacing the transformer the set worked fine. I again looked at the collector waveform. It exceeded my graticule even with he X10 probe but I estimated it to be around 1200Vpp with good symetry. Isn't it odd though that the transistor was spared? BTW, just for my own edification I did some comparison resistance readings (excluding of course the HV winding), between the new and old transformers while they were both out of circuit. There were some very minor descrepancies on two of the LV secondaries in the order of tenths of an ohm but other than that noting jumped out at me. Does anyone know exactly what fails in these things? Thanks for all the help and advice. Lenny Stein, Barlen Electronics.
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