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Sad to say it's likely to be 1 or more transistors in the power amp circuit, although there are other possible causes.
Luckily the repair manual is available (hifiengine.com) and the power amp is built with discrete components, so it should be easily repaired
Most common causes would be an output transistor or dry solder joint(s) due to transistors / resistors getting hot and cooking a solder joint or 2.
Inspect all solder joints carefully with a magnifier, looking for signs of localised heating/burning and/or crysalisation of the solder.
It's normal to replace output transistors as a matched pair even when only one has failed, to minimise distortion. Replacement transistors should of course be as close to the original specs as possible (or better) if genuine parts are not available. The bias will need to be adjusted as per manual (1.5mV emitter to emitter of output transistors).
Good luck.
G'day mate,
I have the exact information that you need. You do not need a service manual to find the part number.
Horizontal output transistor is an S2055n....RCA P/N #230760 found here Flyback assly RCA P/N #262342 foundhereMake sure you work safe with electricity... be sure to disconnect from the supply,and discharge the tube before removing the HV cap. If you have any problems,just let me know. Please rate the advice I have given to you here. Cheers. Good luck with the repairs. regardsrobotek
The Transistors just need the code 2S added to the front of them. Grandata did have the 2SD2390 at just £2.00 plus P&P. They don't seem to have the 2SB1650, in my catalogue, but they could now (2005 catalogue).
If you get an Ohm meter (one to do this job would not be expensive) and connect it accros the transistors you will soon know if a short has occured. As it will act like you have just touch the probes together. You should replace both transistors in each channel that has failed even if only one has gone, to be on the safe side. The only thing else likely to go is bias resistors. A check with the meter will tell you if any has gone, again look for shorts where you wouldn't expect any to be.
go to esservice.com and get the manual from there will be easier as the transistors are directional i believe they are 2sc5707s from memory but you will need to check the transformers and the 2 filter caps on either side of them as if they are faulty will blow transistors.
I have repaired many of these; if a high pitched buzz when you plug the set in---flyback and horz. output transistor are bad--transistor has a generic number on it--Flyback is location number LL05, part number should be 257805---you will find RCA no longer has this part--most now are replaced with an asti #2078----CHECK the RCA number on Ebay---company I get them from is Suburban Electronics---Flyback and transistor are less then 30 dollars for both.
I cleaned the contacts on the transistors and it's working great now. Previously, I spilled some drink on the unit and it went into protect mode and it was in the power amp section. It's all up and running again. Thanks for the info. --Steve B.
The usual cause of this is shorted output transistors. If you have experience with repairs and can solder, you should be able to repair this yourself. Open up the unit and look for the 3-legged parts attached to the heat sink. These are the output transistors. Post here the markings on those parts so I can give you the entire part number. In order to determine the bad ones, you should have an ohmmeter or diode checker. Post the parts markings and we'll continue from there.
Look through the parts index for the horizontal output transistor and the low voltage regulator transistors. Check these for either shorted or open, and also this model is famous for bad capacitors . If you need info on how to check the transistors please refere back to me and I will try and explain how you go about doing it.
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