VX 724 black screen green light flashing

[budm]

Re: VX 724 black screen green light flashing

OK, I see the picture problem now in #2 picture.
I think you may have another problem in the Main logic board due to bad regulator or caps for the video processing. At least try reseating the Ribbon cable from the logic board to the LCD panel first. You may want to verify that you do get good 5vdc from you new board.

[Nocta]

Re: VX 724 black screen green light flashing

So, what you think I should try set the jumper at 7mA and see what happens?

I know pictures are not clear. The problem is, for example, if I have a black square, I see it a bit grey and with green lines. Am I clearer now?

I attached new and better pics.

Thanks.

[budm]

Re: VX 724 black screen green light flashing

That is the jumper to set the inverter board to drive difference CCFL bulbs current as needed for particular lamps since the same board can be used in the smaller or larger LCD panels.
I am not sure what I am seeing in your pictures.

[Nocta]

Re: VX 724 black screen green light flashing

Ok guys, so yesterday the board arrived. I changed it and so far it's working but I have a problem and I don't know what could it be :/

I attach pictures and a video so you can see my problem. It's weird, like if I were set in 16-bit colors :/

I hope you can help me.

PS: The board has a jumper which I can set in 6,5 , 7 or 7,5mA. I didn't change it, it was set in 6,5mA. Do you think that could be the problem?

I'm starting to doubt, maybe the lamps are not working great.

http://tinypic.com/r/1z9gk4/5

[Nocta]

Re: VX 724 black screen green light flashing

I bought a used board for 23 bucks. To be honest, it's much better this way because I don't have to check everything.

@jetadm123 I checked the user and they have 99,9% positive califications. It's a pretty high number. Thanks for that detail because I'm thinking of buying another board. I got a BenQ FP767 and its board has been already manipulated and some components are missing. Instead of buying and looking at a circuit, I'll buy a new/used board too. It's easier and i'm sure it works.

Thanks guys. Even though I bought the board, I learnt a lot here and that's what I appreciate over all!

I would buy used board so you will have spare transistors, transformers, caps. Make sure to inspect the caps by the inveter transformer or replace them since that will cause the transistors to fail when those caps go out.

Thanks for pointing that out. I changed all the caps on the inverter/power board. I also changed (just in case) the cap close to the pins that connects the video with the inverter board and the H154 behind the transformer of the not working lamps (that one was a bit cut).

[budm]

Re: VX 724 black screen green light flashing

I would buy used board so you will have spare transistors, transformers, caps. Make sure to inspect the caps by the inveter transformer or replace them since that will cause the transistors to fail when those caps go out.

[jetadm123]

Re: VX 724 black screen green light flashing

I'm reading the first page of this thread and someone said that the original transistor is 2SC4672, so if I replace it with 2SD1628, should it work too?

For 20 dollars I can buy a working board on eBay and that almost the price of 5 of those transistors in my country (because they've to import them).

What do you think it'd be best? Buy the transistors or a used (but working) board?

Transistors are a tricky lot and there's no guarantee that using a substitute will work. And even if they do work, there's no guarantee that there aren't other problems with the board. If the working board is just a bit more cost wise, then that may be the route to go. Since it is used, check the seller's feedback rating to see if they have been accused in the past of trying to pass off broken parts as working. Good luck!

[Nocta]

Re: VX 724 black screen green light flashing

I'm reading the first page of this thread and someone said that the original transistor is 2SC4672, so if I replace it with 2SD1628, should it work too?

For 20 dollars I can buy a working board on eBay and that almost the price of 5 of those transistors in my country (because they've to import them).

What do you think it'd be best? Buy the transistors or a used (but working) board?

[budm]

Re: VX 724 black screen green light flashing

The Vsat and other spec look great but the current handling is a lot lower than original, you can try, but it may not last.

[Nocta]

Re: VX 724 black screen green light flashing

I checked the CCFL transformers and I got same values on both of them. The transformer where the lamp works gave me the same values than the one that doesn't work.

The only thing left to think are the 2 transistors. I can buy 2SC4672, it should work, right? The Vceo is 30V less than 2SD1628 but Ic and Icp are 2A less than Ic and Icp from 2SD1628.

Thanks for your input, budm.

[Nocta]

Re: VX 724 black screen green light flashing

Great to know. I'll check Vsat, Ic, Icp, etc. Also, I'm gonna try and check the CCFL transformers.

I'll let you know if I have any news. Thanks for your input and quick replies!

[budm]

Re: VX 724 black screen green light flashing

2SB1124 is PNP.

Japanese Transistors:
2SAxxx, 2SBxxx = PNP
2SCxxx, 2SDxxx = NPN

I did not look up the 2SD1624 spec to see if it has Low Vsat, and Ic, Icp (these are important spec). A little lower Vceo may be OK.

[Nocta]

Re: VX 724 black screen green light flashing

I have just seen that you edited your message.

Like I told you, I've already replaced the brown cap. The only thing left is to replace the 2 transistors but I can't find 2SD1628 or the similar ones (as far as I know, these ones should work too 2SD1624,2SB1124,2SC4672).

Thanks!

[Nocta]

Re: VX 724 black screen green light flashing

Yeah, I have already replaced that capacitor too, the brown one. It was a bit open (literally).
I also replaced the big cap for a new one even though it seemed to be working.

Thanks for the quick reply.

[budm]

Re: VX 724 black screen green light flashing

Not sure about the substitute transistors, but one reason the transistor is blown can be due to the bad tuning cap (brown cap next to the inverter transformer), one per transformer. You should take them out and measure the value and the resistance (it should show open with the meter set to highest Ohm range), if the cap is bad, you will damage your new transistors. The not working lamp transistor reading is bad, you should replace them in pair anyway.
More Viewsonic pictures: http://s807.photobucket.com/albums/y...udm/VIEWSONIC/

[Nocta]

Re: VX 724 black screen green light flashing

Sorry for bumping this thread again but I have a ViewSonic VX724 monitor too and it is not working.

I changed all the capacitors and now it shows the image but just for a second and then it powers off (even though the green light is on).

I took out a 2SD1628 transistor because it was broken (I don't know how it could've happen).

The problem now is that THAT lamp (the one where I took off the transistor) doesn't light on. It's not the lamp because I tried switching them, it's the output.

I attach a couple of images. I hope you can help me.

I got the follow reading (at 200 ohm) from the transistor from the other lamp. I write it the way I marked it in the picture.

Working lamps:

1-2 Nothing
1-3 1 ohm
1-4 Nothing

Not working lamps:

1-2 1 ohm
1-3 1 ohm
1-4 1 ohm

I tried but I can't find the 2SD1628 transistor where I live but maybe there's other way to cheat the BI3101A (the one that 'controls' the lamp).

Thanks in advance.





PS: I'd appreciate your input. Consider that i'm not an technician or something.

[cheebster]

Re: VX 724 black screen green light flashing

Hehe, ok. I've ordered a replacement board on ebay for 23$ shipped. Guess i'm somehow giving up on this one, up to some point.

[PlainBill]

Re: VX 724 black screen green light flashing

Hi Plainbill ! Did you play a bit with this one since we last posted ? I got mine still sitting on the shelf waiting for some love. Thanks !!

Sorry, not yet. And moving toward the back of the queue.

PlainBill

[cheebster]

Re: VX 724 black screen green light flashing

Hi Plainbill ! Did you play a bit with this one since we last posted ? I got mine still sitting on the shelf waiting for some love. Thanks !!

[cheebster]

Re: VX 724 black screen green light flashing

I don't 'need' the monitor any time soon, just a spare really.. was on the side of the road.

I redid a lot of the soldering on the board, with fresh solder.. No luck still.

Yes, i'm in Canada.