BenQ 46W1 plasma - Y sustain?? how to be sure??

[sugar_ray]

Sure didn't get much return on this 3K unit from back in 2005. hey......3K was a deal for a plasma back then!! Anyways.....only got 3 years out of it before the dreaded "audio is fine but no video" symptom. Its a BenQ 46W1.

An older plasma to say the least as it only accepts analog inputs, however, it was a beautiful 1080I set when it worked!! Once it croaked I replaced it with a Toshiba LCD which is still kicking. I've had the BenQ collecting dust ever since.

Why I am motivated now to do something?? not sure?? anyways......powers on great, can see screen is working. Audio good just NO video. TV still responds to the remote just fine (on/off, volume up etc...) I am unable to view the menu screen or am unable to tell what input I am on??

What little info I can find on this model. With my similar symptom, I guess (when under warranty) BenQ would just send techs "repair kits" which consisted of 3 boards. Y-sustain, X-sustain, and the logic board. They recommended replacing all 3 at once.

From what I have read the Y-sustain is the likely suspect in my case. I have found a few on ebay etc.....for around the $80 mark. all are used and come from plasmas that had cracked screens. NOT sure if there any new available?

Would it even be worth my time to contact the manufacture (BenQ) and seeing if they even had these parts available considering its an older model?

I wouldn't mind replacing the boards if I can revive it for $150 or so. Just trying eliminate the guess work.

What are the best way for confirming if my suspect Y sustain is bad or good??

thanks

[tom66]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

I believe this is an interesting set. It actually uses a Chungwha plasma panel -- a very, vary rare panel. A limited production run was made for about a year. Now, I have no experience with Chungwha plasma panels, but I imagine the basic details are the same. It's probably a variant of Hitachi/Fujitsu's ALIS technology. A good start would be to post some pictures. Most likely with no video you are talking Y-sustain or Y-buffers. If you can see a glow from the screen it could be the main board or control board.

[sugar_ray]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

thanks for the quick reply Tom

slowly testing components with my meter which isn't the greatest but gets the job done. I pretty much know what every board is. Just have to find the culprit.
Here are a few pics. even enclosed a clear STOCK photo of what my "Y" board looks like

penny for your thoughts......

[sugar_ray]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

Interesting development......sure hope this means something??
the DIF PCB which is located under the input tuner board has an LED on it. one half of the LED is blinking fast RED. the other half of the LED is just a solid green. Just to confirm, this is the LED on the actual board itself. NOT the led on the front of the panel

I could NOT see this before as there was a tin cover over this board. Im no expert.....but I always thought a blinking RED led was a trouble indicator?? When you first turn the set on....the LED is solid green. A second later.....you hear a click (almost like a relay) this is when it would normally go to the BenQ welcome screen. however, it is at this point where the LED starts flashing RED

I circled it in this picture but very tough to tell it is blinking red.

[tom66]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

More than likely, that LED indicates that the board is working. I have no experience with CPT (Chunghwa Picture Tubes) plasma panels, but Samsung panel control boards have a blinking light indicating they are working.

The sustain boards actually look really good! No bad caps (all poly film caps) and lots of decently sized semiconductors. CPT's LCD panels are generally poor so it's interesting to see that their plasma displays are much nicer.

This design of plasma panel has reversed naming. The X-scan (Y-sustain) looks to control the vertical scanning, and the Y-bulk (Z-sustain) looks to provide the alternate sustain electrode waveform.

Can you check if you have good Vs on the Y-bulk or X-scan connector?

[sugar_ray]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

will try your suggestions Tom

Here was an interesting video I found on Youtube regarding a plasma tv with a blinking RED LED> apparently that blinking RED (in his case) meant a FAULT. when he turned the tv on, he had a blinking LED. when he unclipped the Y-sustain board harness and re-plugged in the tv he had NO more blinking light!!

His problem ended up being the Y sustain board

things that make you go hmmmmmmmmmm..... does anyone have any documentation on this model?? like how to enter the service menu??

http://www.youtube.com/watch?v=lHXDH3IEymI

[tom66]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

Ah, but that's the power LED, it's just shining through.

[sugar_ray]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

YES getting good voltage to both boards via the connector. Power supply seems to be feeding all boards nicely. Y-Buffers perhaps??? are they testable??

[sugar_ray]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

just to add.....both Y and Z boards are not only getting proper voltage but they also seem to be OUTPUTTING proper voltage. Both incoming power harness, and out going power harness on these boards appear to be doing what they are suppose to. Same can be said for the power supply board. I would guesstimate this would indicate all components on these boards are fine indicating a good Y and Z?? I am leaning towards Y-Buffer or the DIF PCB but want to be sure before throwing any money at it. I once had a rear projection that was brought back to life by tinkering around, but this seems to be a completely different ball game.

penny for your thoughts.......

[tom66]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

You need to test the outputs with a scope. They are not fixed voltages but variable.

[sugar_ray]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

I assume you are referring to the outputs going to the buffers?? those will yes need the scope. I seem to have nice input and output voltage on the Y-sustain. Can I assume this means the Y-sustain itself is OK. or is it possible the Y-sustain isn't feeding the buffers enough variable voltage?
Thanks again Tom. I have only been on these boards a few days and can tell your huge asset!!

[tom66]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

Unfortunately you really need to use a scope. A fixed voltage could be indicative of a failure, in fact. But I have never tested it myself.

[sugar_ray]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

Tom: thanks for all the help again!! I can acquire a scope but before I do I stumbled across something very interesting.

As previously posted, my DIF PCB (logic) has 2 LED's built on the board. 1 green and 1 red. as soon as I turn the tv on the GREEN led lights up solid. about 2 seconds later the red LED joins in and starts to blink red like crazy!! I could NOT see the fine print on the board before but right next to the LED's it reads

GREEN:READY
RED:BUSY

I would interpit the red (busy) as a fault light. Previously, your best guess was a blinking red meant the board was working. Not sure if this changes your mind?

What is more interesting is when I unplug the "digital video assembly" board which is attached to the logic card the red/busy light will go away and green stays solid. However, by unplugging this harness I lose my tv glow. Plug the harness back in and I get my glow back but the red/busy light goes back to rapid fire.

In a nutshell, hopefully my thinking is on the right track. Either the Logic board or digital main board are what is stopping my picture.

If you were to replace one of these 2 boards or you were a wagering kind of guy, which board would you put your money on that is bad?? Logic or digital main? Both are available quite cheap. May order both for the heck of it. Just hoping I am on the right track?? Lastly.....being an ancient (2004 model) plasma, would you recon that there are any service menu codes for it?? searched the net cant find anything!!

[tom66]

Re: BenQ 46W1 plasma - Y sustain?? how to be sure??

Hmm, well I think of it from another way, maybe. Busy light could indicate that the controller is "busy" and working. A steady lit ready LED could indicate it is ready to work but not running. Of course, I cannot be sure...