When I switch it on i see a very quick flash in each corner of the screen and it clicks as if it would start but it don't and there's no picture or sound whatsoever.
The standby(power) LED keeps blinking twice, which is error code 02 and according to the service manual it means:
"Protection circuit trip < ANY TIME >"
(I have the service manual for it)
NOTE: just before this failure, the unit has been exposed to quite alot of vibrations/shakings when it was moved from a place to another on a trailer. (Please don't ask me why they moved it on a trailer and not in the car, as I have no idea myself. Actually I wonder the same thing! )
Since you have the service manual, I will presume you are somewhat adept and comfortable "going in." You will need a good work surface, good lighting, magnifying glasses and a professional type soldering station.
Suspect cracked solder joints on the PCB, especially where large, heavy components are placed. This includes all transformers (the flyback for sure), items mounted to heatsinks, and can capacitors. The hairline cracks can be very difficult to see, so I usually touch up anything with big leads. Be real careful, though. Many boards are not only dual sided, they could also have circuits sandwiched inbetween. It is not good to to disrupt vias or plated through areas.
With luck, you may be able to bring the unit back to life. There is nothing to loose if it is headed for the scrap heap. If, on the other hand, you want it fixed for cash or under warranty, do not mess with it. Service techs do not like working on stuff that has been altered in any way, even by other techs!
the processor will detect an overcurrent situation for the power supply because line output transistor Q533 is shortened.
The reason this transistor is shortened can be a defective line output transformer, but it can also be that the problem is caused by an insufficient line driving pulse, caused by loose contacts in the line driver stage.
In very rare occasions error 2 is caused due to only a defective line output transformer. Therefore, a good start is to measure the resistance between collector and emitter of Q533.
For your information: this TV carries no double-layer or multi-layer boards.
I measured the resistance between the collector and emitter of the Q533 and I got ~0.8 ohm.
Also, the board was cracked which I fixed, see image:
All the larger solderings for the heavier components is now re-soldered.
Now the thing is that there isn't any quick flashes in each corner of the screen when the TV is powered on anymore, only the degaussing sound is heard. I don't know really but can that be due to that I accidently shortened JR609 and R658/FB611 with the solder? ...there was a pretty wild discharge, it just said boom. My bad.
[ This message was edited by: Martin_R on 2006-01-30 13:24 ]
this don't make the situation easier I suppose ....
The crack is in the primary power supply part. I think you've noticed that the smoothing capacitor for +300V keeps charged in this models, because there is no bleeding resistor present.
You can remove transistor Q533 completely and connect a 100W 230V tungsten lamp between the collector and emittor connections for Q533.
If you repaired the primary PSU side correctly, the lamp must lit (not at full strenght, because it's only operating on 135 Volts then). If that's working, you can proceed with a visual inspection of the solderings of the line driver stage. (See the thread of the earlier mentioned link for details). Or, and that's how I mostly proceed, you can resolder all mentioned parts, replace Q533 and see what's the result.
If Q533 blows again, the flyback transformer must also be replaced.
By the way: I dare to doubt if the repair is worth all the needed effort and cost, because when a PCB crack occurs most of time also the aperture grille of the picture tube comes loose, causing discolorations of the screen. Unfortunately, you can't check this before repairing the set when you don't have another chassis at hand for test.
I've now removed the Q533 transistor and measured it once again betwene the emitter and collector and I get full resistance, with other words no contact betwene them at all. I've resoldered all the line driver parts you mentioned.
I also connected a 100w 230v bulb to the emitter and collector, put all the cables back on the board and switched the TV on. The lamp did not lit though, not at all.
Does this mean that there is something wrong with the primary PSU? And is the transistor Q533 OK?
btw: (when switching the TV on I can still hear a click and the degaussing sound, but there's no quick flashes in each corner of the screen)
[ This message was edited by: Martin_R on 2006-02-02 02:11 ]
according to the measurements you've taken, Q533 is shortened.
You removed the transistor and connected the lamp between the collector and emitter connections on the board, but the lamp don't light at all. This means that the main power supply does not work. This can be because the set is on standby (!), or the repair you did to solve the crack in the PSU-area is incomplete.
If the lamp does not light after pressing 'PROGRAM +' or 'PROGRAM -', you can be sure there is some trouble in the main PSU.
As already said: you have to judge between cost and effort which are needed for this repair and the result. As this is an aftermarket 50 Hz low-end set with a history which don't garuantee a reliable repair, I think the best solution is to stop this repair.
Ohhh man, you're totally right about the standby mode! I should've checked that. Now the worst thing is that I don't have the TV here anymore but left it to a friend to check it out, he has the right equipment, pro solder station etc.
I never tried to change the program to make the TV go into operating mode, but I remember there still were 2 blinks from the standby LED when I plugged it in. So it most likely means the TV wasn't fixed afterall, ...OR maybe it only means that I had a 100w lamp connected where the transistor should be ...damnit! Now I don't know eitherway!
Ohwell, I'll keep you updated on the progress, it'll probably take some days, maybe a week before I know anything.
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