Viewsonic VA720 - 2 secs to black

[retiredcaps]

Re: Viewsonic VA720 - 2 secs to black

Now, how would I measure this on an analog multimeter?

I don't know what your analog meter looks like, but I think there is a 1K and 10K setting? Use 10K Ohms to start.

I'm assuming the inverter transformers are the ones market PT1 and PT2.

I can't tell from the lack of a picture, but they are the ones that sit on the board with the ccfl plugs. The secondary pins might be the ones facing the the ccfl wires (blue pink).

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

I'll post a picture of both the inverter board and my multimeter tomorrow

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

This is my meter:

And I'm fairly certain this is my inverter:

[retiredcaps]

Re: Viewsonic VA720 - 2 secs to black

Well, there is only one resistance setting so use that.

Some of the pin combinations will be low Ohms (less than 1.0 Ohms), and others might show infinite. The one we are interested in is the "in between".

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

I did PT2 first.

Pin layout:
1 -| |= 5, 6
2. -| |- 7
3. -| |- 8
4. -| |= 9, 10

Note: 5-10 are evenly spaced in real life, just couldn't achieve that typed...
I will add readings in a sec

With my Digital multimeter on 2K Ohms

1-2: -0.00
1-3: .217
1-4: .217
1-5: 1.
1-6: 1.
1-7: 1.
1-8: 1.
1-9: 1.
1-10: 1.

How's that so far? Do you need more information?

[PCBONEZ]

Re: Viewsonic VA720 - 2 secs to black

.

1 -| |=5,6
2 -| |- 7
3 -| |- 8
4 -| |=9,10

.

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

.

1 -| |- 5
2 -| |- 6
3 -| |- 7
4 -| |- 8

.

I updated my post.

[retiredcaps]

Re: Viewsonic VA720 - 2 secs to black

I did PT2 first.

With my Digital multimeter on 2K Ohms

1-3: .217
1-4: .217
How's that so far? Do you need more information?

217 Ohms looks like the magic number. Test PT1 pins 1-3 and 1-4.

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

PT1 results: 1-3: .216 1-4: .216
Looks like that one is OK
What's next?


Edit: I checked the PSU output again (now that I have a real meter lol). It's at a steady 12.26V when monitor is off. I turn it on, it dips to about 12.15V when the backlight is on. Then the backlight dies it goes back to 12.26V I guess the panel does not use much power as it is the same voltage as when off.
I hope those readings are normal.

[retiredcaps]

Re: Viewsonic VA720 - 2 secs to black

PT1 results: 1-3: .216 1-4: .216
Looks like that one is OK

216 and 217 Ohms are within 3% of each other so we now can say the inverter transformer is likely good.

Edit: I checked the PSU output again (now that I have a real meter lol). It's at a steady 12.26V when monitor is off. I turn it on, it dips to about 12.15V when the backlight is on. Then the backlight dies it goes back to 12.26V.

That sounds right. The 12V rail is likely to be unregulated and will drop a bit with load.

1) On your inverter transformer, see if there is a SMD fuse or fuses. Two or more fuses will cause 2 seconds to black. If the inverter transformer only has 1 fuse, you wouldn't get 2 seconds to black at all.

2) If you have a spare lcd monitor kicking around that works, you can use the ccfl from that monitor to test out this one. You don't have to remove the ccfl from the working spare monitor. You just have to stretch the cable so that it reaches the other screen.

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

I'll look for fuses tomorrow.
I can't do the CCFL test because (while I do have 2 more monitors) I don't want to take them apart...
But the fuse idea sounds promising, I'll investigate that tomorrow. Those would be marked F or PF, right?

[retiredcaps]

Re: Viewsonic VA720 - 2 secs to black

Those would be marked F or PF, right?

Yes. On an older 2002 heritage NEC monitor, it had an inverter with 2 fuses on it.

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

OK. I'll take a look tomorrow.

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

OK I found this big blue thing marked F1 and I measured it. It shows -0.00 on the 2k resistance setting.
I've circled and indicated F1 in the attached image

Anythnig else I should test?

[retiredcaps]

Re: Viewsonic VA720 - 2 secs to black

It shows -0.00 on the 2k resistance setting.

Anythnig else I should test?

For fuses, you generally want the lowest Ohm setting on your manual ranging multimeter (200 Ohm) so you get more digit resolution. Having said that the fuse is good.

I can't tell from the pictures, but it looks like the ccfl cables are not the 2 wire scenario. If that is correct, you may have a hard time finding a compatible lcd screen that fit those connectors.

I picked up two 17 inch monitors and both have 2 seconds to black. I haven't had time yet to test them, but both have 3 wire connectors so at least I can stretch out the ccfl cables for testing purposes.

If you don't have the 3 wire compatible lcd, you will have to take apart the lcd panel and check for bad wiring and/or bad ccfl as I discussed in the earlier posts.

If you find bad wiring, you may be able to resolder the ends and make it work. If it is a bad ccfl, the cost of replacing it is questionable at best for an 8 year old 17 inch monitor, but that is for you to decide how to spend your money.

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

Any other possibilities for something to check? I really don't want to try taking apart the panel...

[Scenic]

Re: Viewsonic VA720 - 2 secs to black

got a similar size panel you could connect to the inverter?
or some of those modding CCFLs?

If you connect these up and they stay on... well.. CCFL probs in the viewsonic panel

[shovenose]

Re: Viewsonic VA720 - 2 secs to black

I don't have any spare CCFLs. So am I pretty much out of options?

[retiredcaps]

Re: Viewsonic VA720 - 2 secs to black

I don't have any spare CCFLs. So am I pretty much out of options?

If you look back at post #2, there are only the caps and ccfl lamps/wiring left to check. The fuse and inverter transformer test okay.

I don't know if you want to spend the money to recap this old 2003 monitor. Caps would probably cost you $8 and it may NOT fix the problem.

If you have the room, keep the monitor in case you get another one.