Question about RCA P52921 52" Rear Projection Television

2 Answers

56" RCA projection TV (FLYBACK related problem)

Hello! I just replaced the FLYBACK transformer on my 56' RCA rear projection TV model P52921 (Flyback part # 239111, Chassis CTC195M). The HOT was not replaced and I believe the new FLYBACK is not an original part. Anyhow, after replacement the TV powered up and initially the picture looked fine. However, everytime the unit is powered up there is a hissing noise coming from the back that lasted for 3-4 seconds then it disappears. The TV worked well with the exception of the noise and a slight blurr at the very right edge of the screen. The TV worked in that manner for about 7 days until today it did not power up as it did before replacing the FLYBACK. Without any testing and with those two clues (the noise and picture blurr) can someone help me understand what might the problem be? It could be anyone of these: The new FLYBACK, the HOT blew, Driver and HOT base circuit components, the LV regulator, or maybe bad soldering to the new FLYBACK. Any good ideas? Thanks

Posted by Haitham Moaty on

  • 6 more comments 
  • Haitham Moaty Jan 16, 2007

    I made sure that the FLYBACK has the correct part # number (239111). Can the hissing nise possibly come from the HOT?

  • Haitham Moaty Jan 16, 2007

    No it not an original part but a replacement for the original FLYBACK part # 239111. I bought it from a retailer based in Orlando Florida called ACME Enterprises.

    The only physical defect I can see on the new FLYBACK is the beginning of a dark spot at the top of the transformer (Looks like a burnt spot).

  • Haitham Moaty Jan 16, 2007

    maybe a ring test first to rule out the FLYBACK? except I don't know how to perform one, maybe you can direct me to a good tutorial link to understand the ring test?

    Also, how can I test the HOT? is there a specific resistance that I should get across it? Could the HOT possibly cause the HV leakage from the FLYBACK?

    I thought that the FLYBACK usually takes the HOT out with it but I am not sure if the HOT can also affect the FLYBACK causing it to have a leakge and make a hissing noise.

  • Haitham Moaty Jan 16, 2007

    You guys are outstanding!! thank you very much for the valiable information!

    My last question relates to the hissing noise and the flyback possibly going out after 7 days of operation. Can a bad HOT by any chance cuase the flyback to have a HV leak and make a hissing noise?

  • Haitham Moaty Jan 17, 2007

    so is the horizontal output drive same as the HOT?

  • Haitham Moaty Jan 17, 2007

    Ok what would solve the problem is for me to know both the location numbers and part numbers for those two HOTs (the horizontal output transistor and trnasformer). If you can provide me with this information I will be very thankful!

  • Haitham Moaty Jan 17, 2007

    I will assume that the horizontal drive transformer is the same as the horizontal output transformer (please correct me if I am wrong), thanks!

  • Haitham Moaty Jan 17, 2007

    I see, that makes things clear. Can you provide me with their part number or at least tell how to obtian them form a web based database? thank you very much!!

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Anonymous

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The base to emitter of the hot will read short on a diode checker/test on ohms it vairies but typically about 50 ohms.e to c, or b to c should have very high resistance. unsolder the collector of the hot. make sure all solder is gone. now test the ohm between your tuner ground & the pad of the hot collector it should read open.

Posted on Jan 16, 2007

  • Anonymous Jan 16, 2007

    the hot could go bad by itself & not affect the flyback. but if the flyback goes bad i have often found the hot bad as well.

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Anonymous

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Well usually the hissing sound comes from a leaky flyback. maybe the one u bought for the replacement did work for a while but gave up suddenly. this part should be replace by the same specs, otherwise it might create another problem.

Posted on Jan 16, 2007

  • 3 more comments 
  • Anonymous Jan 16, 2007

    no. HOT doesnt emit a noise like this. remember flyback is shielded and coated, any leak will produce a noise like this. try to inspect if theres any physical defect on the flyback. did u bought the flyback in RCA?

  • Anonymous Jan 16, 2007

    try to look also at the horizontal deflection circuits (hor. oscillator, pre-drive, drive ckts.) and possibly power supply circuits

  • Anonymous Jan 16, 2007

    Horizontal output transistor usually has a damper diode across C and E and a bias resistor included between E and B. these internal components alter one's expected ohmmeter test of H transistor; here's how. the base to collector junction will test as a diode, but E to B will show a low resistance, approx. 50 ohms in both directions. now the E to C ohmmeter test will test as a diode. the foregoing results indicate a good transistor. readings other than these indicate a bad H output transistor.

  • Anonymous Jan 17, 2007

    there's another HOT which is the horizontal output transformer. wherein the hor out transistor output is connected.
    hor driver is before the hor out transistor so, its a dirrent thing.

  • Anonymous Jan 17, 2007

    horizontal driver is not a transformer, its a transistor connected directly to the hor. output transformer then to the horizontal output transistor then to the flyback.

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