17IPS02-2 (technika 19in lcd No Power)

[blackillusion]

Hello all, I am very novice at all this my friend gave me this to tinker with. Dead 19in Technika.

So i opened it up IC800 had blown up so not so good. Replaced that. Replaced fuse and it blew straight away. Found 3 out of 4 of the diodes D800-D803 to be shorted so i have replaced them. No the tv doesn't blow fuses which is good right? But still no power. Could anyone give me some pointers into what I should be looking at?


thanks guys

edit: No 5v standby at L805

Trying to follow the schematic

[Turnip]

Hi,

Often happens that the chopper feedback opto-isolator and associated zener diodes go phut after a chopper pop - wouldn't mind a copy of your shematic, don't seem to have one, but have several duff panels.

Good luck - Chris.

[blackillusion]

Hi Chris cheers for the reply, I must say your all over these threads nice to see that.

I've attached the pdf I found.

I don't appear to have DC voltage anywhere. Tested the big cap with my esr meter and reading is fine. I will have a look at the opto-isolator.

[blackillusion]

Just to update zener diode is shorted. Is there a way to test an optocoupler with a digital multimeter? It has resistance over 4-3 and over 1-2.

[blackillusion]

Replaced zener and optocoupler. The Optocoupler that came off seems to be fine as similar readings as new one. The main capacitor when testing with the esr was rising does this mean it is leaky?

[Turnip]

Hi B/I,

Thanks for the shematic, hope you've sorted the set, if not, some voltages, perhaps.

Not met a rising ESR - suspect battery in your meter - Chris.

[blackillusion]

Hi Chris, not a problem.

On with the set, nope I haven't got very far. I am a novice so still learning a lot. Reading through LCD repairs by justine yong and testing the voltages. I fluffed up and blew the voltage regulator and looks like a transistor and a zener again. So have replaced the regulator and zener. I get 244V ac at the rectifier diodes. I get DC 340V over the filter capacitor - isn't that a bit much?

Also I don't get a stable voltage out of the VCC pin from the regulator, might be because I have replaced the transistor Q810 (the coppers are visible).

[Turnip]

Hi there,

Haven't read the Justine Yong bit, but would suggest you try a new panel from "ChasHyde" and mend the other at your leisure.

340v at the filter is normal, as is the 244 AC input - it's a matter of checking all pre-chopper transformer components for failure - any duff bits can pop the rest at switch on.

Tough life - for the dedicated telly basher - Chris.

[blackillusion]

Indeed its all fun and games. Well the fact is I'm learning and using this one to learn. Its a spare time thing and no rush to go anywhere so can take as long as I want. Obviously this is a power supply fault. I need to replace transistor Q810 and would be back where I was before blowing the regulator IC.

[jimca007]

can I make a suggestion to protect your nice new components and , in an emergency you !
Make up a wee extension lead with a 100 watt light bulb ( ordinary lamp bulb ) in series with the live before it reaches the socket of the extension and use this to test your repairs.
if you have a severe overload the bulb will light and remain lit. If it gives a wee falsh and goes out the loads pretty normal and if it flashes the psu's trying to come up and overloading.
It's basic it's cheap and it's easy but can save a right few quid in blown components !

[Turnip]

Hi Jimca,

Goes without saying, have such a socket originally used for checking degauss function and mains bridge problems on tube tellies.

Have found with flat-screen stuff that the bulb flashes and set cuts to s/by indicating maybe no obvious initial problem, or remains on if the chopper snubber or drive is duff and that new power FET fitted is now solid copper.

Still use it though - saves on changing fuses - Chris.

[jimca007]

too true on some of the wee stuff I change down to a 60w bulb doesn't let quite as much current thro before lighting up.
The only thing you've got to be aware of is some SMPS's won't come up with a load in series even if there's no fault, but then as I said it's a wee cheap save-all not fool proof but helps us fools !

[blackillusion]

Thanks for the tips guys, I will look a doing that. Haven't had any more time to play as of yet been a bit busy. Would buy a panel but they are a bit expensive and I haven't exceeded the price of a replacement in part costs yet, when I do I will consider.

Are there any images that I can use to refer to, to make this extension sound simple enough but want to be double sure after all it is electricity were messing with.

[jimca007]

Don't have pics sorry, but it's very simple... get a 3 core bit of flex . cut it in half.Bare the 3 cores in one end of each of the 2 pieces to about 12 inches, cut the neutral and earth wires back to a length of about 2 inches. Get a mains jointing block, the type with the cable grips if you can get one, use this to join the neutrals and earths in the same way you would making a normal joint. bend the 2 long lives back out the ends of the cable grips . so you've joined the cable and closed the jointing box and your left with the 2 lives . Get a surface mounting Bayonet light fitting and secure it to a bit of board or your workstation whatever just so it don't move about, it will after all carry mains voltage. The 2 lives you have are now connected to the live and neutral connections of the light fitting. Fit a bulb ! wee sets about 60 w, med about 100w and the biggies like 42 plasma's etc you may even need to go up to a 150w ( please note these need to be filament bulbs not these energy savin florescent things ! )
So thats the middle part taken care of and your left with the 2 ends of the cable fit a plug to one end and a socket to the other and bobs your uncle you got a surge protector !   

[jimca007]

incidentally i haven't had the time to look them up to see what , if any , the difference is but I've got a couple of 17IPS02-1's , you can have one if you want to cover the postage. just google them for a diagram and check the outputs they look much alike....