Cross a sharp LCD TV with a BenQ, what would you get? (Part 2)

Discussion in 'General Electronics Chat' started by R!f@@, Jun 3, 2009.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    Continued ...

    [​IMG]

    Here is a comparison of both the Inverter Assy. As you can see there is a major difference in them. The High Voltage generation technics is obviously different and the Input Vcc is also quite different. The BenQ uses a 14V Supply and the HV generation is quite similar that of a LCD monitor.
    It uses a step up Tx and the primary is driven in push pull stage with a common low profile high Voltage transistor that is typically found in LCD monitors. Now these transistor's failure rate is quite high as I have found, mainly shorting out but in this case for the time being none of them have any faults besides the Tx and connector. So I bypassed the faulty stage feed back and Powered the Invereter using a separate supply and enabled the switch on terminals, the back lit switched on as before and went pssssssst, pssssst and pooooooooof and up came smokes [​IMG], I went like What the.???
    I mean bypassing a stage never did this to me before. And to make things worse a few of the output stage transistor went up in smoke too. So the sharp inverter is next in line. The Sharp Inverter uses 400V DC to power up and it's drive technics is quite different. It a uses a single output stage to drive a single transformer coupled to a number of isolation transformers and uses opto's in the feed back loop to sense the HV loading. Quite complex and the best part is all the inverter boards are functional, so my guess is this technics is quite reliable and it also generated less heat. The difficulty was to get 400V DC without using the sharp PSU, even if I rectify AC mains the max is 280V DC. It uses a charge pump to increase the 280V to 400V. So I had to use the sharp PSU some how. So that's final. Next part is to interface the BenQ tubes to the Sharp Inverter.
    Below is a picture of both the Tube Assembly dismantled.

    [​IMG]

    [​IMG]

    As you can see the number of tubes is same and identical, even though they from different manufactures. The Connectors was different, so I have to compromise.
    [​IMG]
    I removed the BenQ tube connectors and replaced them with sharp ones so that I can use the sharp inverter. A hectic job though. Never the less it was assembled as shown below and ready to power up.

    [​IMG]

    Part 3

    Rifaa
     
  2. count_volta

    Active Member

    Feb 4, 2009
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    Why not keep all these in one topic?
     
  3. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    760
    Can't. I can't post more than 6 images :confused:

    Rifaa
     
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