HIU-607 (HPC-1518) inverter problem

[orbanp]

Hello Everyone,

The above inverter is in a Benq DV2680 LCD TV. The back-light works fine for about a minute or so and after that it shuts down.
The control signals to the inverter (on/off, dimming) are the same after the shut down.
The inverter is running on 24V. I have checked the power supply, all the caps
are OK, the 24V is there, there is no increasing current draw.
The 24V gets to the Royer inverters, it gets through the fuse and the FET switch on the inverter board, even after the shut down.
There is nothing visually amiss on the board, no darkened or charred components.
The board feeds eight tubes (it may be four U-shaped tubes), with four dual transformer Royer circuits. Beyond those there are a number of comparators, but no dedicated control IC.

Does anyone have by chance a circuit diagram of the board? (The board has some tiny SM
components, it would be hard to draw out that part of the circuit.)
Any other advice on how to proceed with the testing/repair?

Thanks, Peter

[PlainBill]

Re: HIU-607 (HPC-1518) inverter problem

Hello Everyone,

The above inverter is in a Benq DV2680 LCD TV. The back-light works fine for about a minute or so and after that it shuts down.
The control signals to the inverter (on/off, dimming) are the same after the shut down.
The inverter is running on 24V. I have checked the power supply, all the caps
are OK, the 24V is there, there is no increasing current draw.
The 24V gets to the Royer inverters, it gets through the fuse and the FET switch on the inverter board, even after the shut down.
There is nothing visually amiss on the board, no darkened or charred components.
The board feeds eight tubes (it may be four U-shaped tubes), with four dual transformer Royer circuits. Beyond those there are a number of comparators, but no dedicated control IC.

Does anyone have by chance a circuit diagram of the board? (The board has some tiny SM
components, it would be hard to draw out that part of the circuit.)
Any other advice on how to proceed with the testing/repair?

Thanks, Peter

At the risk of repeating myself, "A picture is worth a thousand words". Do not post pictures inline, use 'Manage Attachments' - below the text entry area. And to paraphrase retiredcaps, 'Two seconds to black can be caused by bad caps, a bad CCFL or wiring to a CCFL, a bad transformer, or sense circuit problems'.

There are numerous approaches. By far the easiest is to substitute a known good CCFL in turn for each ccfl in the TV.

In the absence of a spare CCFL, the easiest is to test the secondary resistance of each transformer. They should match to within 3%.

Disassembling the LCD panel to the point you can observe each CCFL is a third (less desirable) option.

PlainBill

[orbanp]

Re: HIU-607 (HPC-1518) inverter problem

Hi Bill,

Thanks for the tip of checking the secondaries of the transformers, apparently one of the coils is open.
I did find a replacement transformer at lcdparts.net. They claim it is for the HIV-607 board, however, the part number is a bit different. They are selling HIT2820521J versus HIT 282 042J that is on my board. I wonder if the last four characters are a date code? I sent them an e-mail asking them.

Thanks, Peter

[PlainBill]

Re: HIU-607 (HPC-1518) inverter problem

Hi Bill,

Thanks for the tip of checking the secondaries of the transformers, apparently one of the coils is open.
I did find a replacement transformer at lcdparts.net. They claim it is for the HIV-607 board, however, the part number is a bit different. They are selling HIT2820521J versus HIT 282 042J that is on my board. I wonder if the last four characters are a date code? I sent them an e-mail asking them.

Thanks, Peter

You are correct, that's probably a date code or production lot. The one I had only the first 5 characters were significant, the last 6 were date code, production lot, or FRU number of the person who wound it.

PlainBill

[orbanp]

Re: Update - HIU-607 (HPC-1518) inverter problem

Just a quick update.
I did receive the replacement transformer finally, installed it, and now the backlight stays on!
I also did find about a dozen questionable (with higher ESR than the good ones) electrolytic capacitors on the main board that I also replaced.

Thanks for the help, Peter

[PlainBill]

Re: Update - HIU-607 (HPC-1518) inverter problem

Just a quick update.
I did receive the replacement transformer finally, installed it, and now the backlight stays on!
I also did find about a dozen questionable (with higher ESR than the good ones) electrolytic capacitors on the main board that I also replaced.

Thanks for the help, Peter

Thanks for the feedback.

PlainBill