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Equipment Repairs => LCD TV forum => Topic started by: norman on April 16, 2008,17:47:21

Title: lcd invertor boards
Post by: norman on April 16, 2008,17:47:21

Hi folks, I have been in the TV trade for 35 years now and I am looking for help on repairing invertor boards. I have had very little success in repairing them, I have checked transformers, capacitors, connections to no avail. Does anyone have fault finding information on these. Do you know of an inverter circuit that could be built to check lamps or a jig that could be built to repair/check invertor boards. Sorry for all the questions but I look forward to any replies. I hope I can be of help to anyone looking for information in the future. Norman.

Title: Re: lcd invertor boards
Post by: rebel-mc on April 21, 2008,17:15:25

Hi, I would normally just replace a small (2,4 or 6) invertor with a generic type.  I have fixed a few invertors by replacing some of the surface mount diodes or transistors.  But this has only been by robbing parts off another board.

Title: Re: lcd invertor boards
Post by: TE on April 21, 2008,17:29:00

DIEMEN, SA launches the first CCFL tester lamp for LCD TV which is able to check lamps for LCD screens from 10” to 42”. The CCFL lamp analyser for LCD TV provides a diagnosis for the lamp on the panel television/monitor without having to dismantle the part of the panel housing the lamps and without having to unplug the different connectors interacting between the inverter and the lamps. It gives a full, reliable analysis so in case the instrument indicates a bad functioning of one or several lamps, the panel can be dismantled and the lamp replaced with complete safety. When the instrument indicates that the lamp works correctly, this means that the breakdown is on the inverter board. This tester provides a significant reduction on the time spent on the repair since you avoid to uselessly dismantle the TV.

http://www.hrdiemen.com/products/eng/detall_noticies2.php

Title: Re: lcd invertor boards
Post by: norman on April 22, 2008,16:31:38

Thanks for the replies, I am slowly getting better at invertor repairs, I feel I spend too much time fault finding only to find I can,t locate spares. As we are all aware the price of invertor boards particularily for small screen tv's makes them uneconomic to repair. Thanks again for the input. Norman :wallbash:

Title: Re: lcd invertor boards
Post by: Ohm Supplies on April 23, 2008,14:02:36

Hi Norman

We find mostly the transformers are faulty.  We have even had a few boards where all the transformers have been faulty!!!!! Its just a learning curve learning how the transformers read and noticing the differencs between them, but I'm sure you'll get there.

We do sell transformers if you ever want to check us out.

www.ohmsupplies.co.uk

Kind Regards
Michelle

Title: Re: lcd invertor boards
Post by: norman on April 23, 2008,17:31:36

Hi Michelle, I never considered all the transformers being faulty, I try to compare readings between them. I have used your company for PSU repair kits and had very fast service from you. I will bear that in mind if I need any transformers. Thanks Norman. :ciao:

Title: Re: lcd invertor boards
Post by: tv tony on May 18, 2008,05:22:20

has anyone considered ringing the transformers as we used to do on old valved line output stages, anyone remember valves? i built an oscillator using a couple of 555's at about 15khz, its never let me down. the freqeuncy is not over critical. if anyone requires a circuit i will willingly post it on here, the existing 24v is supplied to the inverter and the device is fed to the gates of each fet involved, this method of ringing the transformer is reliable and also tells you if the protection has operated, or if the lamp is faulty, thanks for reading, tony walker

Title: Re: lcd invertor boards
Post by: norman on May 18, 2008,08:29:30

Hi Tony, thanks for the reply, I use a lopt tester as described in the television magazine a few years ago. It checks for shorted turns etc. I think the test frequency was about 100 khz. I would be intersted in seeing a cicuit for your version. Thanks again for the input. Norman:brinda:

Title: Re: lcd invertor boards
Post by: BC109 on May 18, 2008,10:23:36

I'd be interested in any test methods and/or CCT for LCD back light inverters & lamps. As Michelle says transformers seem to fault, which I general measure resistance or impedance across coils.

Title: Re: lcd invertor boards
Post by: u s perera on May 25, 2008,11:05:46

even if you fault find spars  are not avalable try www.dlec.co.uk tel no 01634 686 900 for slavaged and new a indipendent co

Title: Re: lcd invertor boards
Post by: Ohm Supplies on May 25, 2008,12:59:29

TV Tony

Can you post the cct?

Regards
Michelle

Title: Re: lcd invertor boards
Post by: BC109 on May 25, 2008,19:45:59

Some times it's better to fault find than just replace boards:
Is it the Lamp or inverter question,
We may have a similar board laying around to get parts from,
Old tech's inbuilt need to repair it,
and of cause COST.
So any ideas or circuits on testing inverters & CCFL backlight, would be great.