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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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RCA CTC169 B+ Problem?
I have got a 46" RPTV RCA CTC169 chassis that has the proper B+ voltage in
Stand-By: 143.5V. However, when I turn the TV on the B+ drops to 114V. The audio is fine and I have OSD but the convergence is not right and I do not have full vertical or horizontal deflection. Has anyone seen this before with this chassis? Thank You! Sam |
#3
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There are at least two, maybe more caps in the regulator circuit that will
affect the B+ level because they affect the operating parameters of the regulator ic. "Jason D." wrote in message ... On 28 Dec 2004 00:38:54 GMT, (John Del) wrote: Subject: RCA CTC169 B+ Problem? From: "Sam Pzapht" Date: 12/27/04 1:37 PM Eastern Standard Time Message-id: I have got a 46" RPTV RCA CTC169 chassis that has the proper B+ voltage in Stand-By: 143.5V. However, when I turn the TV on the B+ drops to 114V. The audio is fine and I have OSD but the convergence is not right and I do not have full vertical or horizontal deflection. You can unload the sweep section and use a 100 watt light bulb as a load on the 140 volt line. If the voltage is normal, you have a load on the supply. If the voltage stays low, the power supply is the problem. Monitor the raw B+ during run; I've run into bad solder on the bridge rect that will cause a severe sag under load. John Del Wolcott, CT CTC169 has two regulator feedback circuits. One for standby mode via this IC (burst mode) and cold side feedback in run mode. You have problem with run mode feedback circuits, it is made up of few transistors and few resistors, some has precision resistors, sealed pot (do not adjust this!) this run feedback monitors the B+ output. Cheers, Wizard |
#4
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I do not have a schematic on this particular chassis, can anyone tell me
which transisitors and/or resistors I need to look at? Will they be on the primary side of the chopper transformer or the secondary side? Thanks! "Art" wrote in message ... There are at least two, maybe more caps in the regulator circuit that will affect the B+ level because they affect the operating parameters of the regulator ic. "Jason D." wrote in message ... On 28 Dec 2004 00:38:54 GMT, (John Del) wrote: Subject: RCA CTC169 B+ Problem? From: "Sam Pzapht" Date: 12/27/04 1:37 PM Eastern Standard Time Message-id: I have got a 46" RPTV RCA CTC169 chassis that has the proper B+ voltage in Stand-By: 143.5V. However, when I turn the TV on the B+ drops to 114V. The audio is fine and I have OSD but the convergence is not right and I do not have full vertical or horizontal deflection. You can unload the sweep section and use a 100 watt light bulb as a load on the 140 volt line. If the voltage is normal, you have a load on the supply. If the voltage stays low, the power supply is the problem. Monitor the raw B+ during run; I've run into bad solder on the bridge rect that will cause a severe sag under load. John Del Wolcott, CT CTC169 has two regulator feedback circuits. One for standby mode via this IC (burst mode) and cold side feedback in run mode. You have problem with run mode feedback circuits, it is made up of few transistors and few resistors, some has precision resistors, sealed pot (do not adjust this!) this run feedback monitors the B+ output. Cheers, Wizard |
#5
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Probably in the right area, ESR the Electrolytics in the regulator area.
SAMS Photofacts are available. "Sam Pzapht" wrote in message ... I do not have a schematic on this particular chassis, can anyone tell me which transisitors and/or resistors I need to look at? Will they be on the primary side of the chopper transformer or the secondary side? Thanks! "Art" wrote in message ... There are at least two, maybe more caps in the regulator circuit that will affect the B+ level because they affect the operating parameters of the regulator ic. "Jason D." wrote in message ... On 28 Dec 2004 00:38:54 GMT, (John Del) wrote: Subject: RCA CTC169 B+ Problem? From: "Sam Pzapht" Date: 12/27/04 1:37 PM Eastern Standard Time Message-id: I have got a 46" RPTV RCA CTC169 chassis that has the proper B+ voltage in Stand-By: 143.5V. However, when I turn the TV on the B+ drops to 114V. The audio is fine and I have OSD but the convergence is not right and I do not have full vertical or horizontal deflection. You can unload the sweep section and use a 100 watt light bulb as a load on the 140 volt line. If the voltage is normal, you have a load on the supply. If the voltage stays low, the power supply is the problem. Monitor the raw B+ during run; I've run into bad solder on the bridge rect that will cause a severe sag under load. John Del Wolcott, CT CTC169 has two regulator feedback circuits. One for standby mode via this IC (burst mode) and cold side feedback in run mode. You have problem with run mode feedback circuits, it is made up of few transistors and few resistors, some has precision resistors, sealed pot (do not adjust this!) this run feedback monitors the B+ output. Cheers, Wizard |
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