Fixing Toshiba Regza 37" LCD TV

[ABuNeNe]

Hi I got this Toshiba Regza 37" LCD TV, model is 37AV550E.

It work fine for about 30 mins and after that the picture will goes blank with the audio will playing. I shined a torch light and can see the picture moving.

I opened the back and found no bulging capacitors on the power supply, main and the inverter boards.

Is this the problem with the inverter or the t-con board?

Also does anyone know which remote control can work on this TV?

[tom66]

Re: Fixing Toshiba Regza 37" LCD TV

Do you have a digital multimeter available?

[ABuNeNe]

Re: Fixing Toshiba Regza 37" LCD TV

Do you have a digital multimeter available?

Yes, I've this cheap multimeter.

[tom66]

Re: Fixing Toshiba Regza 37" LCD TV

OK, check that the 24V to the inverter board(s) is present and steady.

[ABuNeNe]

Re: Fixing Toshiba Regza 37" LCD TV

OK, check that the 24V to the inverter board(s) is present and steady.

Hi I found out the inverter board I'm using is this, 6632L-0541A.



I can see there are only 2 connectors connected to this inverter board, top left hand corner and middle bottom. Am I correct to say the power connector is the top left hand corner? Is yes, I unplugged the cable and there's only 1 blue wire running inside, any idea how can I measure the 24V?

[addytzu123]

Re: Fixing Toshiba Regza 37" LCD TV

Hi,

The power connector is in the middle bottom, looking at the photo.
Pins 1 to 5 are +24V / pins 6 to 10 -24V and pin 12 is inverter On or Off.
The connectors from the top are the outputs to the CCFL lamps. Be careful, there is a high voltage on those connectors (> 1000 V)

[ABuNeNe]

Re: Fixing Toshiba Regza 37" LCD TV

Hi,

The power connector is in the middle bottom, looking at the photo.
Pins 1 to 5 are +24V / pins 6 to 10 -24V and pin 12 is inverter On or Off.
The connectors from the top are the outputs to the CCFL lamps. Be careful, there is a high voltage on those connectors (> 1000 V)

Thanks for your reply.

So I put my multimeter's red probe on either one of the pins 1-5 and the black probe on either one of the pins 6-10?

[selldoor]

Re: Fixing Toshiba Regza 37" LCD TV

Seems like a problem with the inverter or bulbs/wiring but may not be.

When the set is on test the voltage on the small white fuse on the inverter board with respect to ground.
When it goes off do the same.
Is there any flickering just before it goes off?

Also when it is on try heating the inverter board with a hairdryer to see if it goes
off quicker. If not try the hairdryer on other boards (looking for a bad solder connection}

[addytzu123]

Re: Fixing Toshiba Regza 37" LCD TV

Yes, correct. You should read a voltage close to 24V. Keeping the negative lead on pins 6-10, place the red probe on the fuse labeled F1, 12A/65V, on the side closest to the capacitor C2 and you should also read +24V. If not, double check the fuse with multimeter on Ohms scale (200) and the TV off. If reading close to zero Ohms > fuse ok, if reading 1. then the fuse is open (shortcircuit somwhere on the board).

[ABuNeNe]

Re: Fixing Toshiba Regza 37" LCD TV

Something strange happened when I opened the back, turn on the TV and tried to wait for the picture to go black so I can measure the voltage but it did not happen. It should happen after running for about ~30mins but it've been running for more then an hour and it still working fine.

Any idea what happened?

[addytzu123]

Re: Fixing Toshiba Regza 37" LCD TV

First thing through my mind - bad solder joints. Since you have pinched/pulled/pressed the connectors while testing, maybe some contact may have been reestablished, either on inverter side or on the power board side.
Some real photos front/back would shed more light into the issue.

[selldoor]

Re: Fixing Toshiba Regza 37" LCD TV

MAGIC

Maybe the moving about has moved a bulb wire slightly or when you switched it on. a spark caused solder to melt on a bad joint and resolder itself.

These are both reversible fixes so the test will come when you switch it off and on again.

If posting more pictures please use manage attachments rather than posting in line or offsite
when the images will disappear

[ABuNeNe]

Re: Fixing Toshiba Regza 37" LCD TV

Yes, correct. You should read a voltage close to 24V. Keeping the negative lead on pins 6-10, place the red probe on the fuse labeled F1, 12A/65V, on the side closest to the capacitor C2 and you should also read +24V. If not, double check the fuse with multimeter on Ohms scale (200) and the TV off. If reading close to zero Ohms > fuse ok, if reading 1. then the fuse is open (shortcircuit somwhere on the board).

Hi the problem come back again and I'm finally have time to do this test now.

I've measured the F1 fuse using the multimeter's continuity mode and there beeping sound so the fuse should be ok right? Anyway if this fuse is broke, it should have the problem from the start right?

I've also measured the 24v input to the inverter and it's 23.7v, will measure again when the backlight goes off.

Am I correct this is the test if the problem is caused by the power supply or the inverter board? When the backlight goes off, if the input voltage to the inverter is not ~24v then there's something wrong with the power supply board and if the ~24v is ok then there's something wrong with the inverter board?

Anything else that I should also measure while waiting for the backlight to go off?

[ABuNeNe]

Re: Fixing Toshiba Regza 37" LCD TV

Previously, while in standing mode and with the back cover on, the backlight will goes off after 30mins but it've been almost 2 hrs now and it's running fine.

The difference is now the tv is lying down with one side supported, no back cover and some screws have been removed on the main board to allow easy access to the inverter board connector.



What's happening?

[ABuNeNe]

Re: Fixing Toshiba Regza 37" LCD TV

Update, the tv is still running fine since power on.

I highly suspect it's due to overheating on one of the components, maybe capacitor (I still can't find any bulging capacitor) or one those of components on the power board with the heatsink, which is causing the backlight to go off when the back cover is attached.

Anyone can confirm my findings? Is it safe to touch the heatsink on the power supply board? If yes, any idea is it possible to attach a fan and draw 5v power from the power supply board?

I also found this youtube video.

[martino]

Re: Fixing Toshiba Regza 37" LCD TV

I'd say it's because the cover is off now,the heat can escape a little easier....
Time to get the hair dryer out and heat up some boards?

[selldoor]

Re: Fixing Toshiba Regza 37" LCD TV

DO NOT touch any heatsinks whilst the set is powered up or for 15 minutes after.

What you can do it to apply extra heat to the boards using a hair drier to see
if the set goes off.

Problem could still be wiring to the bulbs in particular the top set as they normally get hotter than the rest. Also lying the board down may have moved the wires.

[ABuNeNe]

Re: Fixing Toshiba Regza 37" LCD TV

Ok, I placed the back cover back and less then 30 mins the backlight goes off. I measured the input 24v voltage to the inverter board by placing the black probe on pin 6 of the connector and red probe on the F1 fuse side closer to the capacitor C2 and it's 23.9v.

So can we rule out the power supply and the main board are working fine and is this the case of the bad inverter board? Could it also be the problem with the t-con board?

[selldoor]

Re: Fixing Toshiba Regza 37" LCD TV

Its difficult to rule anything out as there is interaction between the boards.
You really need to do the hairdryer thing to pinpoint the problem.

[ABuNeNe]

Re: Fixing Toshiba Regza 37" LCD TV

Its difficult to rule anything out as there is interaction between the boards.
You really need to do the hairdryer thing to pinpoint the problem.

Sorry can provide more details on how does the hair dryer thing will help to pinpoint the problem?

Is it to blow hot air on to the top of the different boards when the tv is on, one at a time and if the backlight goes off, the board that is currently blowing would be the cause of the problem?