Sharp LC-37B20E difficulty accessing service mode

[dkneyle]

I'm getting a blink code which indicates a lamp problem. Following guidance I see on YouTube etc, the suggestion is to re-set the lamp failure counter before going too far further. I use the technique described in Sharp service manual to enter Service Mode (hold down INPUT and VOL DOWN key simultaneously then power up) and it seems to half get there before shutting down again. The Power LED goes through a different sequence than standard start up, a brief flash from the backlights, audio static burst, then it shuts down again.

Do you reckon things are too far gone and the set is shutting down even in Service Mode to protect itself?

Thoughts please?

[nomoresonys]

Re: Sharp LC-37B20E difficulty accessing service mode

Try holding down input and vol down while plugging in power cord.

[nomoresonys]

Re: Sharp LC-37B20E difficulty accessing service mode

Maybe this: Unplug the television.
Press and hold the "Channel Down" and "Input" buttons on the panel.
Plug the television back in while holding down these buttons. ...
Keep holding the buttons until the television powers back on. ...
Use the remote to navigate the "Service Mode" menu and select "Factory Reset" from the menu.

[dkneyle]

Re: Sharp LC-37B20E difficulty accessing service mode

Yes mate, that is what I'm doing. And as I reported in my first post, something a bit different does happen, but it still shuts down just before service menu starts up

[nomoresonys]

Re: Sharp LC-37B20E difficulty accessing service mode

Try holding volume down+channel up+power.

[R_J]

Re: Sharp LC-37B20E difficulty accessing service mode

If you have a bad ccfl (broken) or bad transformer on the inverter, the tv will shut down for protection. If this is the case, you will not be able to bypass the fault using the service menu.

[nomoresonys]

Re: Sharp LC-37B20E difficulty accessing service mode

Do you have an image or text or anything when you shine a flashlight at the screen when you hit menu? Check that fuse on the inverter board.

[nomoresonys]

Re: Sharp LC-37B20E difficulty accessing service mode

Try heating the inverter board with a hairdryer, small section at a time be sure and hit the capacitors, see if the tv comes on for longer or if anything changes, pretty good inverter testing video here, not your exact model but gives the basic idea, check for any bad/cold solder joints too as instructed: https://www.youtube.com/watch?v=hIn5gQzMWsE

[dkneyle]

Re: Sharp LC-37B20E difficulty accessing service mode

If you have a bad ccfl (broken) or bad transformer on the inverter, the tv will shut down for protection. If this is the case, you will not be able to bypass the fault using the service menu.

I'm pretty sure this is the situation. I can see the CCFL tubes briefly come on then the TV shuts off. I doubt there is anything wrong with the inverter. I've told the owner it is likely a write-off and he has donated to me.

As part of my learning curve I'll probably pull the panel down to access the CCFL tubes. I'll buy one of those cheap CCFL tube testers from China and see what that shows.

The issue remains that even once I've identified the problem it still looks uneconomical to repair. A set of CCFL tubes coming out of China is getting close to A$100 landed here. I considered converting to LED and might look more into that. Here is a good video of a guy doing it on a larger version of this TV: https://www.youtube.com/watch?v=jdk-GxU7TU4

I'll update this post as I move along with this project. A good looking TV that I'd like to save if possible.

[R_J]

Re: Sharp LC-37B20E difficulty accessing service mode

Sometimes the connector that grips the ccfl wire corrodes and this can cause a problem, also try removing the inverter and have a look at the screw ground connections, If the metal looks black and the inverter side contacts look black, try cleaning the grounds and see if that helps. Also check the resistance of the transformer secondaries, if you fine one that is different, it could be defective
Converting to led and you will likely be changing burnt led's soon also

[dkneyle]

Re: Sharp LC-37B20E difficulty accessing service mode

Just a question about removing the inverter board from your experience. Years ago when first getting into this hobby I recall removing an inverter board and ending up with broken ends of CCFL tubes on the clips of the board. Is this going to be the same situation here? Do I need to remove the tubes first before taking off the inverter baord?

[R_J]

Re: Sharp LC-37B20E difficulty accessing service mode

I'm not 100% sure on this inverter, It is possible the black connectors DO go into the panel and hold the ccfls.
I found this bulletin, You could download the service mannual from https://elektrotanya.com/sharp_lc_37...wnload.html#dl

[dkneyle]

Re: Sharp LC-37B20E difficulty accessing service mode

I'll go carefully and if they don't slide out (as you'd indicated in your post before editing) I won't force the point!
If the board does slide out, I suppose I could check the functionality of the lamps with a CCFL tester without opening up the panel?

[R_J]

Re: Sharp LC-37B20E difficulty accessing service mode

If you look at pictures of the inverter board, the black connectors are part of the inverter, so the board does not slide out, I also uploaded a bulletin that is part of that manual download. Here is the panel breakdown
It looks like the ccfl's are connected to the holders and they are attached to the metal panel, the black connectors on the inverter should just come loose from the holders. See page 4 of this manual

[dkneyle]

Re: Sharp LC-37B20E difficulty accessing service mode

Thanks RJ. I see what you mean from the exploded view. And I've also seen that arcing/corrosion before that you mention, on other panels I've stripped down. Will let you know how I go.

[dkneyle]

Re: Sharp LC-37B20E difficulty accessing service mode

Clever boys you both! Got inverter out without any drama. Ran the ohmmeter over the secondaries of the transformers. Consistent value is about 1.8k. However, T7504 was many Kohms. About 43k actually. Now to see if I can track down a T51.0186.211 transformer to suit.

[dkneyle]

Re: Sharp LC-37B20E difficulty accessing service mode

Looks like I'm going to have to buy a complete inverter board. Type RUNTKA334WJZZ Backlight Inverter VIJ38002.50. I should be able to get one landed in Oz for about A$50, making it a 'just economical' repair I think? High quality TV and the owner has agreed he'd like to get it going. I think it actually has sentimental value to him. Purchased in the UK, it spent time in Ireland, and now it is in Oz. You can tell it's an import because it uses SCART connectors which are non-standard here. But it also means there's no local spare parts. Mind you, most TVs over 10 years of age don't have much in the way of local spares down here.

[dkneyle]

Re: Sharp LC-37B20E difficulty accessing service mode

Just to bring the thread to a conclusion. Got a new inverter board from China, installed, and panel lights up, working just fine.

I'm starting a new thread. This TV was brought into Australia from UK. We have a different channel plan so it won't tune to our DTV channels. I'm questioning if a firmware change is possible to make it operate in the Land of Oz.

[dkneyle]

Re: Sharp LC-37B20E difficulty accessing service mode

Anyone coming across this thread and looking for inverter transformer T51.0186.211, I have stripped the good transformers from the inverter board and listed them on that common auction site. A$20 each. Just put T51.0186.211 into the search function on the website and you should find them.