Grundig GU15WDT inverter bodge needed

[ProDave]

15" freeview LCD tv.

Inverter shuts down after about 5 to 10 minutes. I suspect aged backlight tubes out of spec.

So I need to disable, or modify the inverter's shutdown parameters.

It's an all in one PSU / inverter board:

Proview Technology Inc
PI-XXXXTLTX VERSION:A
200-001-XXXXTLTX-AH
DTAE:2007/08/10

The main chip is a TL494C

Anyone know how to make it a bit more forgiving of aged ccfl tubes?

[watteau]

Hi,
Here's a list of overides I have, can't remember where I got them from.

Inverter Protection Circuit Over-Ride.
By AMIT
For Test Purposes ONLY!!!!!!

A few tips to cancel protection :
IC TYPE:                CONNECTION:

BIT3105            CONNECT 5.6V ZENER TO PIN 2
OZ9925       CONNECT GROUND TO PIN 12
494            2.4V ZENER TO PIN 3
BD9983            2.4V ZENER TO PIN8
0Z960           LED TO PIN10

Regards,
John

[Turnip]

Hi Pro-Dave and thanks John,

Had similar prob, and duff tubes quickly get worse - change them if tube checker cuts out. Think PS/Inverter is a Vestel IPS (under that Proview label) but such problems point to backlight CCFL, esp with an initial pink piccy - Chris.

[ProDave]

I did come up with a fix bodge.

I sumised it might be over voltage, so I fitted an extra load in the form of a 4.7 megohm resister across each inverter output.

That initially worked and the set ran for a whole evening.

But soon the problem was back.

Yes the tubes do start up with a distinct pink hue, and I opened up the panel and had a look and the ends of the tubes are severely black.

So yes the correct repair is new tubes, but frankly on this particular set it's not worth it.

So it's one to be dismantled, the main board and PSU / inverter to be sold on ebay and the screen kept just in case I get another one with a smashed screen (but good tubes) in the future.

[sparky]

hi
i have a gu16wb2 no dtv had any probs or how to get into
service menu seems to work ok thro scart
thanks dave

[ProDave]

hi
i have a gu16wb2 no dtv had any probs or how to get into
service menu seems to work ok thro scart
thanks dave

No idea.

I have another one of these, the 15" version with DVD player. The DVD is broke, the screen is poor and freeview does not work, so it's kept as a hack set for use in the workshop for testing things with scart or hdmi etc.

I wonder if the freeview fault is the same?

In my set if you select DTV you get the blue text in the top right saying "DTV please wait" while the freeview bit boots up, then you just get a blank screen.  This is true of any attempt to access any freeview function, even channel setup, installation etc.

Hence why that old set is just kept as a workshop hack, it's otherwise worthless.

Incidentally, the DVD version of this set has a different inverter (just an inverter as the DVD version has an externel 12V PSU) and that is more tolerant of duff tubes and works okay with my duff screen. But that's not a solution due to the other faults with that one.  And any attempt at combining bits from and and bits from another would result in a mongrel of a set, again with no value.


What main board is in your set?  if it's the same I have the main board for this one for sale since I've now decided to scrap the set.

[sparky]

hi
it sounds like the same fault no opened it up
yet works fine scart
dave