LG 32LC56-ZC 2 sec to black, and Standby--sorta....

[Alastair E]

This set is rather an odd Backlight/going to stby fault....

From Stby, turn set on. Will start up, show picture then within a few seconds, (2-6 secs) of turning on, the backlight will either blink once or twice or just blank out--backlight off, then go to standby, within half a second or less.

The 'ERR-OUT' voltage is constant at 1.8v, except when the backlight is off or blinks. disconnecting this wire from the MB doesnt affect the fault in any way.

Turn on again, will repeat. Its one of these combined PSU/Backlight types, and Ive confirmed the PSU is working and the backlight is good along with the PSU part that runs it by making 'Inv-C' and PS-ON 3V from the STBY 5V via resistor.
ERR-OUT stays constant 1.8V during this test.

Had backlight running for about half hour no probs at all. The MB was disconnected during this run/test.

It appears the Mainboard is turning the backlight off intermittently then it goes to standby.

Any ideas?

[Alastair E]

Re: LG 32LC56-ZC 2 sec to black, and Standby--sorta....

After some research--seems like there's issues with this series of mainboards. Here is a SVC that indicates some inductors that can cause this and various other faults--

http://www.tv.quuq.org/forum/index.p....0;attach=1251

However, It didnt help in my case....

There's also a series of caps on the mainboard--that cause a variety of picture faults...
--a kit with the circuit ref numbers here--

http://www.ohmsupplies.co.uk/REPAIR-...4040-LG-32LC56

Again--This didnt fix my fault however!

[audiofreak19]

Re: LG 32LC56-ZC 2 sec to black, and Standby--sorta....

It sounds like there might be a ccfl bulb bad. Those symptoms are very common for that fault. Test it by taking panel out and turn on to see if all the bulbs fire up at same brightness

[Alastair E]

Re: LG 32LC56-ZC 2 sec to black, and Standby--sorta....

Aye--you would have thought so--But I can get the BL to run faultlessly by 'Potching' the PSU/BL board. (PS-On and INV-C to +3V)

The BL in this set I Think is a single tube, wound back/fourth down the screen zig-zag style--bit like a fridge condenser-coil--, there's only two connections to the backlight tube, and a single HV transformer on the PSU board...

Wiring a std. 20W CCFL energy-saver domestic bulb (Stripped of its internal electronics, so just the tube) to the transformer, will flash brightly very briefly twice, then thats it.

Wiring the same CCFL in series with the original BL, and the fault is identical to without it,--ie no change, although the additional CCFL bulb lights at the same time as the BL, and at normal brightness.

I did find a thread on another forum going on about firmware, and potching the set to force it to stay on, similar to above but with MB connected. Might try that, but very dubious on that thread's contents about 'one firmware fits all' so-called-- advice, so wont be messing with the F/W.....

[Alastair E]

Re: LG 32LC56-ZC 2 sec to black, and Standby--sorta....

Well--It gets stranger and odder!

I got hold of another 32LC56-ZC today--What Luck!

This one was dead. No LED, No life--nothing. Examination showed that four 2200uF 10V caps to be rather sad.

I grabbed the PSU out of the first set above fitted it and with confidence--fired it up.
--Or rather--Not!

Exactly the same fault as the first set. It would start up, show a picture for a second or so, then back to standby.

Oh dear!

I decided to repair this second sets PSU and replaced these bloated caps--with some 3300uF 10V Panasonic as these were all I had of the same physical size.

Fitted this back in the second set--which then fired up normally and ran until I pulled the plug.
I removed its PSU and fitted it to the first set--Which also worked faultlessly.

So the fault is PSU based--Even though I can get the PSU to run faultlessly on its own by making PS-On 3V and Inv.C 3V, it will supply all the voltages correctly and run the backlights, with no flickering or blinking of the BL.
All electrolytics have been replaced with good quality, low ESR ones--Although there was nothing wrong with the originals.

I decided to swap over the HV CCFL Transformers--even though the boards are just slightly different, one from set 2 being a V1.1 the other, the faulty one being V1.3 the transformers test and look identical.

The fault stays with the faulty V1.3 board. So--Its not that transformer....

I dunno--Strange one.... All I can say for certain--It Aint The Mainboard.

[Alastair E]

Re: LG 32LC56-ZC 2 sec to black, and Standby--sorta....

Right-- a bit more work done.

There is a pin of the PSU marked, ERR. Guessing 'error'

This with the good, working PSU sits at 4.9V.

With the bad PSU during the time the set is active before standby is sitting at 2.09v

Removing the wire from the plug at the PSU and attaching this lead to a 3.7V polymer batt, the set will run normally and not go to standby.

So--Chicken/egg. Is there a fault somewhere--Or is the error circuit at fault! I dunno, cant find a diagram for this EAY38639701 PSU anywhere.....

[ReeceyBurger123]

Re: LG 32LC56-ZC 2 sec to black, and Standby--sorta....

Update ?

[Alastair E]

Re: LG 32LC56-ZC 2 sec to black, and Standby--sorta....

Ha--I botched it!

Wired the err pin to the 5v rail. Set is still running fine however--2 years later...

[ReeceyBurger123]

Re: LG 32LC56-ZC 2 sec to black, and Standby--sorta....

Sweet