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TV repair...

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Marks256

New Member
I have a small 14" Orion CRT TV that i got for Christmas from my parents about 6-8 years ago. It has a nice remote, but the remote just stopped working about 3-4 years ago. I know for a fact that the remote still works just fine, because my remote works on my Sister's TV. So, i know that the problem is with the TV.

Since i have NEVER taken apart a TV, what do you think the problem is? Could it be that the IR Receiver in the TV burned out?

I am thinking of tearing it apart next weekend. What are some safety precautions i should use? I know i need to discharge the CRT, if i want to live to see tomorrow :). So, to do that, all i need is an insulated screwdriver(grounded to the frame), and put it under the "suction cup" on the cathode tube? That wont wreck the TV, will it?
 

tunedwolf

Well-Known Member
There is a slim chance you could pop the final rectifier in the loptx by blasting the static like that, 99 times out of 100 you will get away with it, but ya never know. Better to use a 100k resistor with a wire attached and a croc clip on the other end taped to a well insulated screwdriver. Clip it to the braid that goes round the back of the tube, then carefully peel back the suction cup and poke the resistor lead inside the anode and hold it there for a minute or two. Remember if you leave it hanging there, to remove it again before you power the set back up.

The original fault of the remote not working could be a few things, first off, most of the newer sets don't use just a photodiode anymore, they use a 3 legged module that is screened from daylight and rf, so maybe if you're luck it's just dry solder joints...if not, the three connections are usually Vcc Gnd and data...so a quick scope check will show you if there is any data being put out, if you haven't got a scope, a logic probe will do to listen to the data stream...
Unless you have a scope and can actually see the data coming out, it's going to be hard to tell if it's just a clock or if it's actually sending out something useful. Power supplies are always supsect, so check them first off, just be careful where you stick your fingers and your meter probe. If all else fails you will need a copy of the service manual I'm afraid.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
tunedwolf said:
There is a slim chance you could pop the final rectifier in the loptx by blasting the static like that, 99 times out of 100 you will get away with it, but ya never know.
Never heard of such a thing! - there's no path through the rectifier, so no way of causing damage to it. Although, admittedly, it's 'nicer' to discharge using a resistor! - although I never have, nor seen anyone ever do it!.

But in any case, there's no need whatsoever to discharge the CRT - UNLESS you're removing the anode cap for some reason?.

The original fault of the remote not working could be a few things, first off, most of the newer sets don't use just a photodiode anymore, they use a 3 legged module that is screened from daylight and rf, so maybe if you're luck it's just dry solder joints...if not, the three connections are usually Vcc Gnd and data...so a quick scope check will show you if there is any data being put out, if you haven't got a scope, a logic probe will do to listen to the data stream...
Failure of the IR receiver IC's is quite common, you need to be aware that they don't all use the same pin connections though! - 'usually' the centre pin is 5V, and the outer ones are Gnd and data out.
 

tunedwolf

Well-Known Member
Nigel...I have seen one blown in front of me by just this very thing, it's not that there is a path per se, it's purely the static discharge that does it.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
tunedwolf said:
Nigel...I have seen one blown in front of me by just this very thing, it's not that there is a path per se, it's purely the static discharge that does it.
I've been doing it 35+ years, as has every engineer I know - and I've NEVER heard of it causing a problem.
 

tunedwolf

Well-Known Member
it was a Finlandia, but I'm buggered if I can remember what model now...
I hated those sets anyway, with their damned thyristor flybacks...
Not that it matters particularly, I know it can happen, so I merely suggest he takes steps so that it can't...
 

Nigel Goodwin

Super Moderator
Most Helpful Member
tunedwolf said:
it was a Finlandia, but I'm buggered if I can remember what model now...
I hated those sets anyway, with their damned thyristor flybacks...
Not that it matters particularly, I know it can happen, so I merely suggest he takes steps so that it can't...
I can only imagine it was because the multiplier capacitors (inter-winding capacitance for diode-split) was charged up?. It's certainly never a concern normally - but on the other hand, why would you be discharging the tube anyway, except to replace either the CRT or the EHT rectifier/LOPTX?.

Finlandia were rubbish anyway! - but we did lots of Grundig sets with thyristor LOPT.
 

Marks256

New Member
But in any case, there's no need whatsoever to discharge the CRT - UNLESS you're removing the anode cap for some reason?.
So it would be safe for me to service the TV without discharging the CRT? Even if i plan to solder/desolder?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Marks256 said:
So it would be safe for me to service the TV without discharging the CRT? Even if i plan to solder/desolder?
Yes, even assuming the CRT is charged up you can't touch it, as it's under a big insulating cap - which is far away from the PCB.
 

tunedwolf

Well-Known Member
hehe, you're so right about them being rubbish, built like a tank, but as reliable as the average Fiat at the time. I put them in the same category as Grundig and Normende. Most times we were removing the chassis completely, hence having to discharge the tube.
 

Hero999

Banned
What about the other capacitors on the board? Surely it's a good idea to discharge them too.
 

Marks256

New Member
Would it be effective if i were to unplug the tv, and then hit the power button? Would that discharge anything?
 

tunedwolf

Well-Known Member
it wouldn't make much difference as the mains switch is on the primary side of the switchmode....just place a 100K resistor across the larger caps for a few seconds each all around the power supply and you should be ok...
 

HiTech

Well-Known Member
If your sister has the same tv set, just swap yours with hers when she's not home. :eek: :rolleyes:
 

Marks256

New Member
If you're that scared of the TV I seriously suggest you DON'T bother taking the back off!
I'm not SCARED of it. This will be the first time i have taken a TV apart, and i want to make sure i don't screw up. :)

If your sister has the same tv set, just swap yours with hers when she's not home.
That is actually a great idea, except for the fact that they are TOTALLY different. For some reason they have the same remote control codes, but they are two very different TVs. Hers is like two years newer, and it is by some other japanese company. :p
 

Hero999

Banned
They probably just use the same remote control ICs, many TVs do.
 

Marks256

New Member
Thanks. I will give her a look-see when i get a chance, or when the medications wares down..... :) don't ask....
 
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