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viewsonic VX800 LCD

i got these two monitors VX800 nice looking 18" LCD desktop monitors that use an external power brick. my research sez the brick is 12vdc at 5A. my plan was to makeshift something, i found a 3mm? plug to fit the power jack and wired it to the 12v drive molex line on an old AT power supply form the 486 days pre-ATX. the 12v rail is rated at 8A. the grren light on the moniotor comes on but flashes display text the POST screen on the PC flashes it only for a second.

i can repeat that 1 second by cycling the power button but thats all i can get from it. i tried a 12v rated lass than 2A same responce. i tried the drive molex line from the ATX supply on the PC i'm using tot test it but no green light. i measured the volts on that line and its like 13.5vdc or so.. there was another brick i tried also but no green light and slightly more than 13vdc. so the monitor is picky and refuses 13v+

i havent tried the other monitor yet. im expecting someone already knows these are buggy and bet it probably has the same issue.

requesting any assistance u smart people can provide.

Reply to
divx dude
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I was given a Sanyo VIZON 15" LCD TV without its PSU. The 4 pin proprietary jack said 12 volts @ 2.5 amps. I managed to install a common jack and thought I would use an old ATX supply. The ATX supply puts out

12 volts at 10 amps. When measured it was slightly higher at 12.2 volts. I said cool and applied power to the Sanyo. All was well for a few minutes then the backlight started to flicker. Slow at first then faster until it reached about 2 flashes per second. I thought well the inverter is shot. Hooked up 13.8 volts @ 1.5 amps (actually a variable supply) and the flashing stopped at 13.3 volts.

So yes your situation could be similar. Borrow a 0 - 15 vdc supply and see if you can dial in a voltage where the monitor will work.

--
Live Fast, Die Young and Leave a Pretty Corpse
Reply to
Meat Plow

think i can maybe use a POT on a 13.8v supply ? what value pot?

if put it in series after a fixed resistor 2x its value doesnt that focus the variable to the upper 1/3 of the voltage range? in other words would make like 9 - 13.8 vdc variable supply instead of

0 -13.8.
Reply to
divx dude

Look up Ohm's Law and calculate the values yourself.

I=V/R or V=IR or R=V/I V-voltage I-current R-resistance.

--
Live Fast, Die Young and Leave a Pretty Corpse
Reply to
Meat Plow

s

i guess the pot would need to be 5-10 watt , a 5k pot after 4 5k fixed Rs would make approx 11v- 13.8v adjustable. let me know if that sounds right, i'm shaky in this area.

i dont understand something tho. theres a ton of generic viewsonic external DC supplies on fleebay and non of then discuss a specific voltage other than 12v.theres almost a differnet model for every viewsonic but the only differences are the amp rating and the plug tips.

could it be theres a knowm magice voltage number like your 13.3vdc that they all use that isnt widely known to the users?

almost all are around $10 shipped except mine is about $50. it seems that is due to the unusual size of the 3mm plug tip. i'm wondering if i just buy the $10 12v/5a supply for the different viewsonic and hack the end off and wire a 3mm tip (have one) if that wouldnt make it happy.

problem is i only have a 4day period to return this montior.

Reply to
divx dude

ummm...

this is not a supply issue. as discussed in other LCD brands a inverter problem is detected by pressing a flashlight onto the screen to detect display text etc.

i did and i did.

omg.. its full of werds theres werds in there.

Reply to
divx dude

That was the problem with giving the Sanyo VIZON less than 13.3 volts even though the input voltage printed above the DC jack said 12v. If you have an inverter problem more often than not it will prevent the monitor from operating without backlight.

I'd guess that these VX800's have a common inverter malfunction if you got two of them with the same symptoms. As far as my Sanyo goes, flashing backlight at anything between 12 - 13 vdc the work around was to give it

13.8 volts. I don't have the original PSU nor the actual voltage specs. But one would think that if it called for 12 that's what it needed, not 13.8. 
--
Live Fast, Die Young and Leave a Pretty Corpse
Reply to
Meat Plow

Other than the substitute power supply, this is the classic 'two seconds to black' scenario. A backlight inverter is essentially a constant-current AC source with protection features to detect an open lamp or excessive current. The protection is disabled for about two seconds when the backlights are activated to allow the system to reach a steady state. Thus, a persistant fault results in 'two seconds to black.

Possible faults include bad electrolytic caps on the inverter, one or more bad CCFLs, a bad solder joint on the CCFLs, a bad inverter transformer, a shorted transistor, or the real fun possibility, a defective component in the protection circuitry. In theory, slightly high or low voltage should not cause the problem, but it shouldn't be ignored.

The first step is to open the monitors up and look for obvious problems, especially bulging caps. Then you try arranging the monitors in such a manner that you can hook one or more of the CCFLs from monitor A to the inverter in monitor B. If one of the CCFLs in monitor A will result in monitor B working normally you have identified a problem.

PlainBill

Reply to
PlainBill47

thanks for the input guys. i decided to return the monitors to the guy that sold them. amazing how "losing" the power supplies can entice a moron like me into thinking hes getting an easy deal.. not worth the effort.

i do appreciate the tips tho...im sure i will need to fix one sooner or later..

Reply to
divx dude

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