ViewSonic VP171b

[DixiePenguin]

I have a 17" ViewSonic LCD. Powers on, power light stays green but no video signal. Entire screen is white.

Initial check shows no visibly bad caps, however:

EMAX high voltage board has two 180uF 25V Hermei.

Coretronic video board populated with TAICOM caps. Two 1000uF 10v, and one 2200uF 16v (horizontal mount). One 470uF 16V, one 120uf 16v, (14) 100uF 16v, and (4) 10uF 25v.

Power board looks fine and would seem to be okay since it powers up and stays green.

Any thoughts on what to check next?

Thanks in advance.

[Spacedye69]

Re: ViewSonic VP171b

Same thing happens when I forget to plug the cables from the power board to the control board after a repair!!

In other words, I'd check the cables between the boards. Power and inverter seem OK. Signal is not.

[DixiePenguin]

Re: ViewSonic VP171b

I have experienced that "Homer Simpson" moment several times, including cursing a non-functioning system only to realize that I did not power on the rocker switch on the power supply.

I rechecked and all connections were tight. I even made sure that a wire had not pulled free in the connector itself. (I spent a half hour once before spotting a wire pulled out just enough to miss contact.) SO I am leaning toward a non-obvious component failure on the video signal card.

I don't really have much in the way of test equipment yet but hopefully will be able to remedy that soon.

Thanks for the suggestion.

[Scenic]

Re: ViewSonic VP171b

had the same problems (white screen) with my brothers HP L1710 17" LCD...

after replacing all of those Lelon crapcaps it works fine again

caps had no visible failure signs but when i desoldered them they fell into pieces

[DixiePenguin]

Re: ViewSonic VP171b

Thanks, Scenic,
Were the caps on the video signal board or elsewhere? All caps on the Coretronic board are Taicom, which are apparently sort of hit and miss quality. I may try to get enough of the right Pannys or other good brands and replace if I can narrow it down any more.

I have read argued claims that you can do a basic live/dead test with a multimeter on the caps in circuit. What I was to look for was still vague so I don't know if it would help me anyway.

I would love to have an ESR meter but the prices would insure bodily hard from my wife. She only reluctantly tolerates my activities taking over her kitchen as it is.

[Scenic]

Re: ViewSonic VP171b

Thanks, Scenic,
Were the caps on the video signal board or elsewhere? All caps on the Coretronic board are Taicom, which are apparently sort of hit and miss quality. I may try to get enough of the right Pannys or other good brands and replace if I can narrow it down any more.

they were all on the video board, but i replaced the caps on the inverter board too because they got somewhat hot..

but as i couldn't get matching caps in this size i put them between the power board and the video board, secured them with some hot glue and wired them up.

not the best solution and somehow ugly, but it works..

the problem was the height of those Lelon crapcaps.
i soldered the new caps onto the PCBs, tested the LCD and everything worked just fine... well... then i tried putting the LCD casing back together and noticed that the caps were too high to mount the LCD panel with those 2 boards on it back into the back casing..

crap.. double the work
another reason for checking *everything* *before* you start doing anything

anyways.. an impression of this "caps-with-hot-glue-and-lots-o'-SINGLE-COLORED-(!)-wires"-mess...


the pictures name is for a reason

good thing is that i don't need to see this mess anymore as it's put back together and already up and working..
my brother would kill me if he sees this.. (and i bet he'd be not the only one.. :O)

[gonzo0815]

Re: ViewSonic VP171b

Great EMI station but when it is working .....

[Scenic]

Re: ViewSonic VP171b

well.. my brother has to use it.. not me
and he didn't want to pay much
there's also a metal plate covering those 2 PCBs (video & power board)

[kc8adu]

Re: ViewSonic VP171b

Omfg!
Wtf!!!!

[Krankshaft]

Re: ViewSonic VP171b

I could probably make a whole slew of EMP pulse jokes but I'll take the high road .

At least it works.