Toshiba high voltage problem
Hello everyone.
I am working on a 27in. toshiba color tv model CF27G50. Original trouble symptom is that when I push the power button on, the relay clicks supplying power and I could hear the high voltage attempting to build up then just about a second the relay clicks turning the ac supply off. I have tried disconnecting each low voltage power loads to check which circuit or component causes the relay to turn off almost instantly until I reach the high voltage section. When I turn the power button on I see some sparks in the picture tube electron gun - somewhere around the filament / cathode area, then the relay turns off. When I remove the high voltage cap from the picture tube the relay remains on already, high voltage is produced but the weird thing is that when I push the power button on the pcb or attempt to touch any ground connection: wire, heat sink, etc., a high voltage arc jumps from the ground to my finger before my finger touches it and I receive a mild electric shock. Looks like excessive high voltage? But why do arc jumps even when a ground terminal is touched? I tried connecting in parallel the two snubber capacitors - those connected across h.o.t. with a capacitor of smaller value but no effect. I would appreciate any hint, comments or help regarding this problem. Thank you very much. Bobby |
Sparks inside the crt are not normal, probably the source of your problem.
"Bobby Villamor" wrote in message news:F1fod.301087$nl.261429@pd7tw3no... Hello everyone. I am working on a 27in. toshiba color tv model CF27G50. Original trouble symptom is that when I push the power button on, the relay clicks supplying power and I could hear the high voltage attempting to build up then just about a second the relay clicks turning the ac supply off. I have tried disconnecting each low voltage power loads to check which circuit or component causes the relay to turn off almost instantly until I reach the high voltage section. When I turn the power button on I see some sparks in the picture tube electron gun - somewhere around the filament / cathode area, then the relay turns off. When I remove the high voltage cap from the picture tube the relay remains on already, high voltage is produced but the weird thing is that when I push the power button on the pcb or attempt to touch any ground connection: wire, heat sink, etc., a high voltage arc jumps from the ground to my finger before my finger touches it and I receive a mild electric shock. Looks like excessive high voltage? But why do arc jumps even when a ground terminal is touched? I tried connecting in parallel the two snubber capacitors - those connected across h.o.t. with a capacitor of smaller value but no effect. I would appreciate any hint, comments or help regarding this problem. Thank you very much. Bobby |
Art wrote:
Sparks inside the crt are not normal, probably the source of your problem. "Bobby Villamor" wrote in message news:F1fod.301087$nl.261429@pd7tw3no... Hello everyone. I am working on a 27in. toshiba color tv model CF27G50. Original trouble symptom is that when I push the power button on, the relay clicks supplying power and I could hear the high voltage attempting to build up then just about a second the relay clicks turning the ac supply off. I have tried disconnecting each low voltage power loads to check which circuit or component causes the relay to turn off almost instantly until I reach the high voltage section. When I turn the power button on I see some sparks in the picture tube electron gun - somewhere around the filament / cathode area, then the relay turns off. When I remove the high voltage cap from the picture tube the relay remains on already, high voltage is produced but the weird thing is that when I push the power button on the pcb or attempt to touch any ground connection: wire, heat sink, etc., a high voltage arc jumps from the ground to my finger before my finger touches it and I receive a mild electric shock. Looks like excessive high voltage? But why do arc jumps even when a ground terminal is touched? I tried connecting in parallel the two snubber capacitors - those connected across h.o.t. with a capacitor of smaller value but no effect. I would appreciate any hint, comments or help regarding this problem. Thank you very much. Bobby Ive seen a few like this. Try removing the tube base board then take a cler plastic 12" ruler and hook a testlead from the end of the ruler to the ground strap on the tube. Make sure theat no part of the chassis is within 6" of the tube pins. Switch on, and holding the ruler by the end without the wire, bring the wire near then right up to the pins of the tube neck board. If it starts to arc back away and switch off, the tube has leaked and is gassey. BER but save the good chassis. The other common cause of arcing in and around the tube neck is if the ground pin of the Screen/Focus unit on the side of the LOPT is disconnected. Symptoms are, tube base board arcs accross spark gaps even if removed. No arc from tube (may 'fizz' a bit if the EHT is excessive). Close inspection reveals arcing under LOPT. You may be able to mend the broken pin, but LOPT replacement is reccomended if you cant make a good joint onto the remaining pin. -- Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED) ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- & [dot]=. *Warning* SPAM TRAP set in header, Use email address in sig. if you must. |
Sparks inside of a CRT means that air has leaked in, and a new CRT is the
only fix. In the case of this model of TV set, it would be time to get a new one. -- Jerry G. ====== "Bobby Villamor" wrote in message news:F1fod.301087$nl.261429@pd7tw3no... Hello everyone. I am working on a 27in. toshiba color tv model CF27G50. Original trouble symptom is that when I push the power button on, the relay clicks supplying power and I could hear the high voltage attempting to build up then just about a second the relay clicks turning the ac supply off. I have tried disconnecting each low voltage power loads to check which circuit or component causes the relay to turn off almost instantly until I reach the high voltage section. When I turn the power button on I see some sparks in the picture tube electron gun - somewhere around the filament / cathode area, then the relay turns off. When I remove the high voltage cap from the picture tube the relay remains on already, high voltage is produced but the weird thing is that when I push the power button on the pcb or attempt to touch any ground connection: wire, heat sink, etc., a high voltage arc jumps from the ground to my finger before my finger touches it and I receive a mild electric shock. Looks like excessive high voltage? But why do arc jumps even when a ground terminal is touched? I tried connecting in parallel the two snubber capacitors - those connected across h.o.t. with a capacitor of smaller value but no effect. I would appreciate any hint, comments or help regarding this problem. Thank you very much. Bobby |
"Bobby Villamor" wrote in message news:F1fod.301087$nl.261429@pd7tw3no... Hello everyone. I am working on a 27in. toshiba color tv model CF27G50. Original trouble symptom is that when I push the power button on, the relay clicks supplying power and I could hear the high voltage attempting to build up then just about a second the relay clicks turning the ac supply off. I have tried disconnecting each low voltage power loads to check which circuit or component causes the relay to turn off almost instantly until I reach the high voltage section. When I turn the power button on I see some sparks in the picture tube electron gun - somewhere around the filament / cathode area, then the relay turns off. When I remove the high voltage cap from the picture tube the relay remains on already, high voltage is produced but the weird thing is that when I push the power button on the pcb or attempt to touch any ground connection: wire, heat sink, etc., a high voltage arc jumps from the ground to my finger before my finger touches it and I receive a mild electric shock. Looks like excessive high voltage? But why do arc jumps even when a ground terminal is touched? I tried connecting in parallel the two snubber capacitors - those connected across h.o.t. with a capacitor of smaller value but no effect. I would appreciate any hint, comments or help regarding this problem. Thank you very much. Bobby Usually sparks inside the CRT mean the tube has cracked and needs to be replaced. Sometimes they crack under the yoke where you can't see it, I had one I was checkihg out, I went to pull the neck board off and the whole neck of the tube came off in my hand. |
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