Question about RCA F25649 25" TV

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No power hi ! i change flyback and the regulator but the tv not open. i check the value of the output transistor driver but still ok. the power relay go up and back down atfer few second . do you know what i can do for this problem. email thank you !

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Re: no power

Hi, you have a short circuit in the power supply circuitry somewhere - could be a faulty HV Capacitor or a short on the
power supply pcb. The relay wont stay on because there is a short circuit around that area.
hope this helps, good luck.

Posted on Feb 06, 2008

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My aiwa tv has no power

what you can do is trouble shooting of the tv unit. first place to be check will be the powers supply section check weather the primary fuse get blown. if ok check the regulator and the bridge type diode which shorted. if all good, next will be the horizontal output transistor or an open resistance going to the b+ of the flyback transformer.

Oct 04, 2012 | Standard (CRT) Televisions

1 Answer

Horizontal transister heat up and shortens

Try to replace new harizontal output transistor.Before replacing the transistor,check the regulator and the flyback if shorted or not.If the flyback is shorted the harizontal output transistor will be damage again if you trying to turn on again.Thanks..

Aug 26, 2011 | JVC TM-2703SU 27" TV

1 Answer

What causes the horizontal transistor to short? flybak ok, supply line ok. my tv is a samsung with a model #: ct-21k30mh.

You just replace the capacitor fitted very near to the horizontal output transistor,[freewheeling capacitor], there may be one or two of them, whcih comes to a value of 3900pf to 6700pf 2000V or so. It is connected to the negative rail and the collector of the horizontal output transitor. If it gets opened, or its value gets reduced, this fault will occur. If so the transistor you replace will get shorted as you swich on the power to TV.
The second one is deflection yoke short. If so the transistor said above will overheat within seconds. Even a single winding inside the horizontal deflection yoke shors, it puts a tremendous load to flyback transformer, which in turn effects the transistor.
After replacing the above said capacitor, you do one thing to make sure about whether there is a short inside the yoke or not. It cannot be measured by normal methods. Fore that, unplug the base card from picture tube and place it somewhere near without getting any of its contacts to other parts inside your TV. This time only the EHT chord will be connected to picture tube. Unplug the horizontal yoke connection from main board. Switch on the tv, and wait for some time, say at about 10 seconds, and check whether the transistor gets overheated or not If it does overheats now also, the winding or EHT retifier diodes inside your flyback transformer has some trouble, and it should be replaced with same type and number. If it does not overheats now, the deflection yoke's winding have some short in it. Ok.
NB: Never connect the TV with base card is in postion while deflection yoke connection is isolated. keep it unpluged.

Oct 27, 2010 | Samsung Ultra SlimFit 20" Digital TV

1 Answer

Akai 25'' TV no power from SMPS. voltage available up to filter capacitor. No smps output. smps power transistor ok. Please responce

try to check its high voltage section for axed HOT or flyback. Also check its regulator. Maybe start up resistor or check the chopper circuit. You should at least have an standby voltage on the secondary side.

Oct 28, 2009 | Standard (CRT) Televisions

1 Answer


The Horizontal Output transistor needs to be changed as it is most likely shorted. The current transistor on this set is a 2SD3402 (no longer available) it's new replacement part number is the 2SC5902.
Order 2 2SC5902 Horiz Output transistors.Replace the transistor by it self once and if all is ok then fine.
If not replace it again and also the the Flyback HV transformer. The HOT transistor is probably shorted again and the transformer is causing it.

Dec 27, 2008 | RCA 32V550T 32" TV

1 Answer

Hyundai 14" colored tv no power

if the final flyback is ok ,then check the driver transistor and the voltage in his collector .Probably the flyback transformer is ok.please reply.

Oct 17, 2008 | Sharp 25R-S100 25" TV

1 Answer

Sanyo DS31650 31

If the set runs at all, your flyback and output transistor are good. If the set shuts down after a few seconds and the sides are wavy, it usually means that the main B+ in your power supply is too high and not regulating properly. I do not know what kind of power supply that model uses, but if has an old-style STR regulator (like the STR30130) then it is probably shorted, and if the set uses a switching power supply then look for an open or leaky electrolytic cap on the primary side. If the power supply is working correctly and the set shuts down, check for an open safety cap (the large 1.6 - 2Kv cap connected to the collector of the horizontal output transistor).

Aug 17, 2007 | Sanyo HT32744 32" TV

3 Answers

Sony KV-32S40

When the horizontal output (2SC4927) is shorted it means one of 2 things is wrong - the horizontal drive transformer has cracked solder joints or the flyback transformer is shorted inside. If the solder joints on the horizontal drive transformer (the small grey transformer connected to the base of the horizontal output transistor) are cracked then the set will play for a little while and then the parts you just replaced will again be destroyed. ALWAYS resolder the driver transformer when replacing the parts you mentioned! When I replace the parts you mention and I do not see any obvious cracks on the driver transformer then I unsolder the B+ pin of the flyback (labeled 135, for 135 volts) and put a 60 to 100 watt lightbulb (drop-light) in series with the flyback. This means that the 135 volts B+ goes through the lightbulb and then into the flyback, so the lightbulb acts as a current limiter to protect the horizontal output. When you turn the set on the bulb should glow no more than about half bright and you should hear the high voltage come up, but you should not see a picture. If you turn the set on and the bulb glows as bright as if it was plugged into the wall then you can bet that flyback is shorted and must be replaced.

Jul 12, 2007 | Sony KV-32S40 32" TV

1 Answer

Jvc tv

You need to check the horizontal output transistor first for a short,ift he transistor is good check the diodes and low value resistors of the secondary of the flyback(output trasformer),if all those are ok check the crt board,it has low value resistor for the g2 voltage,if ok you need to go back to power supply and check for a short from each one of the diodes to ground for a posiblwe short.Be careful when measuring voltages and use the correct ground.

Oct 01, 2006 | JVC AV-36F702 36" TV

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