Viewsonic went from bad to worse

[Solder Boy]

Wasn't quite sure where to put this question.. the battery for my camera is recharging at the moment so no pics as of yet.

I'm pretty sure the logic board and or the board on the back of the LCD panel is now fried.

Original symptom was that the unit would turn on..stay on for maybe a minute or two and it would go to black and stay black. I had an image on the screen it should be noted. Opened it up.. pretty well all the caps on the power/inverter board were blown except for the one small cap and the filter cap.

I also found a bloated cap on the logic board. I checked the rest of the caps on the logic board with the ESR meter.. all were good.

So after doing the recap job.. assembled it back together.. plugged it in and I heard a quick SNAP followed by wiffs of smoke.. quickly unplugged it. Took it apart again and the replacement cap on the logic board exploded.

It kinda puzzled me because I checked the cap with my cap meter and ESR meter and it read ok.. might also add it was a brand new cap.

Replaced the cap again on the logic board. This time when I plugged it in.. I heard a hissing sound coming from the CCFL's. That quickly went away.

No cap explosions this time.. would this faulty new cap I installed be the cause of no video? I obviously solved the no power problem.. CCFL's stay on but no image. Tried reinserting the LCD ribbon connector.. again nothing?

Again I apologize for no photos at the moment they will be up if need be when the batteries are recharged.

Thing is I have successfully repaired 6 LCD's so far, just wondering if I did something wrong or not check something before I originally plugged it in.

Thanks!

[shovenose]

Re: Viewsonic went from bad to worse

You could have shorted with bad soldering?

[PlainBill]

Re: Viewsonic went from bad to worse

First guess is you installed the cap on the logic board backwards the first time. It is also possible the cap was defective.

It MAY have taken out one of the voltage regulators on the logic card. I'll be able to make meaningful suggestions when you are able to post the pictures.

PlainBill

[Quasar]

Re: Viewsonic went from bad to worse

Model number of unit and maybe the part number on the board?

At least we can try and look up the info...

Q

[mathog]

Re: Viewsonic went from bad to worse

First guess is you installed the cap on the logic board backwards the first time. It is also possible the cap was defective.

The OP didn't say what model monitor it was. There is a bit of a booby trap on at least one Viewsonic model. The VX715 power supply I repaired had the polarity of one capacitor marked one way on the circuit etching, and the other way in felt pen (the pen was only visible once the original cap was off). The correct polarity could be determined from the trace side of the power supply, and it matched the felt pen. One other person (Newbie1) has reported the same thing, see this thread:

https://www.badcaps.net/forum/showthread.php?t=10272

If the OP has this model, or something similar to it, it might be a good idea to read through that thread. Newbie1 put the cap in matching the board etch and it blew, and he (she?) subsequently had a fairly complicated, but eventually successful repair. On mine, the cap went in the right way the first time and there were no further complications. It could be that Newbie's machine was already in worse shape than mine, or it could be that blowing up that cap did indeed inflict the further damage Newbie1 observed.

[mathog]

Re: Viewsonic went from bad to worse

Thing is I have successfully repaired 6 LCD's so far, just wondering if I did something wrong or not check something before I originally plugged it in.

Careful inspection with a magnifying glass before applying power is worth the time. Some solder bridges are very hard to see without magnification.

I also triple check those inter-board connectors which have pins on one board and a socket on the other. The darn things are never keyed and it is easy to plug them in offset by a row (one board slightly higher than the other). Now you might think it would be obvious when this happens, but it isn't always. The extra row of pins can slide in under the socket where they cannot be seen, and when the connectors are fully engaged (with the offset) the plastic on the pin side can cover the empty holes on the socket side.