VX-922 PSU non cap part failures

[boomer400]

Viewsonic VX-922 psu failure :

Replaced a slew of CapXon caps on a vx922 display psu (all radial electrolytics) (P/N 3BS006431CGP REV:1 FSP035-1PI01), and on logic board (3 large radial electrolytics).

Unit now powers up but :
a) the blinking green power on light still shows
b) the video returns correctly and one can see correct VGA images (ie: MS Windows splash and boot screens) but when the power on light blinks , the image flashes and takes a few seconds to refresh and then flashes again, then power cycles, flashes, power cycles, etc. etc.

Close inspection of the failed board shows : (with the OLD PSU.jpg as assistance)
a) long thin component at C1 has some kind of leakage at each end; the leakage is a coppery green powder substance)
What type of component is this? Possibly a diode? Any one know of a part number so I can try to replace it?
b) component at C2 shows some level of heat damage. It may or may not be working and while I have the part numbers (SPI 8LE00081 5P6 HI-POT 0609 GP. Looks like a transformer or regulator, any one ever have this fail?

I ordered a replacement board but they sent one that doesn't fit properly; it's probably for a slightly different model. So I decided to try and resurrect the old board while Viewsonic tries to figure out how to get me a correct psu.

The problem is that although the parts are similar, they do not share the correct connector locations. Attached are images of the items in question :
the OLD PSU.jpg
NEW PSU.jpg

NEW PSU.jpg shows the main problems :
a) the power connector from the PSU to the logic boards is 90 degrees out of place
b) the power cord location is about .5 in offset from the correct location
c) the actual board itself is slightly different in shape and can't fit in the location so there is no way to actually screw it down

the OLD PSU.jpg shows the original board to be replaced :
It had failed and the symptoms were blinking green power on light and no video whatsoever.
a) it had many blown CAPXCON capacitors; all were replaced as a test
b) secondary logic board had 3 additional CAPXCON capacitors also blown, they too were replaced

If anyone can tell me about that leaking piece and confirm about the "transformer" (and if they're available anywhere), it would be great! TIA!

[retiredcaps]

Re: VX-922 PSU non cap part failures

a) long thin component at C1 has some kind of leakage at each end; the leakage is a coppery green powder substance)
What type of component is this? Possibly a diode? Any one know of a part number so I can try to replace it?
b) component at C2 shows some level of heat damage. Looks like a transformer or regulator, any one ever have this fail?

What you call C1 looks like the bridge rectifier. If the PCB marking starts with BD, that is the bridge rectifier. It does not look healthy at all.

C2 is a transformer.

I ordered a replacement board but they sent one that doesn't fit properly; it's probably for a slightly different model.

It is not uncommon for manufacturers to use totally different boards or revisions while keeping the same model number.

a) it had many blown CAPXCON capacitors; all were replaced as a test
b) secondary logic board had 3 additional CAPXCON capacitors also blown, they too were replaced

The light blue caps look like they came from Radio Shack. If yes, Radio Shack does not sell low ESR caps which are required in a SMPS application. Your problems with image flickering and flashing could be the use of these replacement caps on the power and logic board.

[retiredcaps]

Re: VX-922 PSU non cap part failures

1) To test your bridge rectifier, set your multimeter on 200 ohms (if manual). With power off and lcd unplugged, number the pins 1, 2, 3 ,4.

Measure resistance between pins 1-2, 1-3, 1-4, 2-3, 2-4, 3-4. Any reading under 30 ohms suggests it is shorted. You can measure this "in circuit".

Others can suggest on how to clean up that green stuff or if the entire rectifier should be replaced.

2) For the flickering problem, this could be due to unstable power. On the connector between the power and logic board, you are going to measure for stable DC power.

With power on and lcd plugged in, put your multimeter on 20V DC. Put your black probe on a ground screw. Put your red probe on each pin and report each voltage measurement. Pay attention to whether it is stable or fluctuating voltage.

3) Your flickering could also be due to poor soldering of the new caps (or the caps itself). Check your soldering by gently rocking the new caps and see if they solid or not.

[boomer400]

Re: VX-922 PSU non cap part failures

Ok, great, does anyone know what kind of bridge rectifier I need to replace it with? Can't read anything on the original, and it's awfully long and thin. And it's got just 2 legs so it looks more like some kind of diode?
As for the caps, they're not RS but are miscellaneous spares I abused just to see if the thing would fire up. I left the case open while testing and it was just for literally 1-2 minutes max each time. You think that they would cause the power cycling to that extent? Not much in the way of "flickering", it's more like power cycling, turning on and off. Picture seems fine otherwise (no lines and seems bright enough until the thing turns off) Solder joints seem firm and clean, I used brand new solder, not junk.

I'll test the power stability when I get home, that's pretty easy.

[Rtech]

Re: VX-922 PSU non cap part failures

I am sitting looking at the same PSU/Inverter, so here we go :_
C1 is simply a wire link covered in insulation, the green stuff is probaly 'verdisgris' off the wire.
C2 is the input transformer used for suppression,and if it is burnt then you need to change the large smoothing Capacitor next to it.
Other common faults on this board is failure of one of the brown caps at the top pf the board,and the top right inverter transformer which usually burns out,and you can sometimes see that on its underneath.As well as caps of course

[retiredcaps]

Re: VX-922 PSU non cap part failures

C1 is simply a wire link covered in insulation, the green stuff is probaly 'verdisgris' off the wire.

Now that I look at the picture again, I can see the bridge rectifier just below the transformer. It was a bit obscured by the white box and using a 10 inch wide netbook doesn't help either.

[boomer400]

Re: VX-922 PSU non cap part failures

I am sitting looking at the same PSU/Inverter, so here we go :_
C1 is simply a wire link covered in insulation, the green stuff is probaly 'verdisgris' off the wire.
C2 is the input transformer used for suppression,and if it is burnt then you need to change the large smoothing Capacitor next to it.
Other common faults on this board is failure of one of the brown caps at the top pf the board,and the top right inverter transformer which usually burns out,and you can sometimes see that on its underneath.As well as caps of course

Hmm, ok, well then I'll assume that the wire link I can just leave alone (I'll clean off the powder). I wonder if it's possible that it might be too heavily oxidized inside the insulation.

The large smoothing cap you refer to must be the one in the center (off the top of my head, I think that was something like a 1000 microfarad, 400v) which I did replace. But should I bother to even find a replacement input transformer? The one there is really nasty looking, for sure but I tried to find it online briefly and couldn't find a proper match for the id nos. on it.

The inverter looks ok or at least in better shape, underside of the board doesn't show much burnout residue.

Bridge rectifier (I left the part no. at home looks ok, I can read the numbers just fine on it and it doesn't look like its been overheated) looks ok.

[retiredcaps]

Re: VX-922 PSU non cap part failures

Bridge rectifier (I left the part no. at home looks ok, I can read the numbers just fine on it and it doesn't look like its been overheated) looks ok.

Yeah, that is my bad. I was viewing the pic on a 10 inch netbook (as explained in my other post).

[Rtech]

Re: VX-922 PSU non cap part failures

It may be the photo,BUT the right hand Brown cap at the top looks as though is has bulged,compared to the left hand one ???????/also measure the secondaries of both the inverter transformers, to ensure they are both similar,Should be between 3%-5%differece ONLY between the two readings ??

[Rtech]

Re: VX-922 PSU non cap part failures

As far as your questions are concerned:-
Replace the link if you so desire(I would)
The burnt looking input transformer are pretty standard on most Monitor boards,if you have access to any other types, it would be worth a look,to see if they will fit dimension wise.

[boomer400]

Re: VX-922 PSU non cap part failures

well, it turns out that Viewsonic doesn't supply the older PSU board version any more so I'm screwed. So, I'm back to square one and am going to try to revive the old PSU.

I'm going to get Nichicon caps to replace those generic blue caps and to replace the single tiny CapXcon 10microfarad 50v cap in the center of the board. It's the only one on the PSU I haven't touched so it's worth a try. Do any of the other disc caps ever blow?

Rtech, I'm going to change that brown disc cap too, you're right, it looks awfully funny too. Probably do both of them.

As for the wire link, what's a good substitute?

As for the burnt looking input transformer I don't have any thing to try as a replacement. Anyone have any ideas as to what would be a good replacement to order?

Geez, looking like I'm redoing the whole kit and kaboodle, anyone got one of these units in working condition for sale?

[mathog]

Re: VX-922 PSU non cap part failures

The burnt looking input transformer are pretty standard on most Monitor boards

A little browning of the circuit board under that transformer isn't uncommon, but that transformer is way past that point, it looks fried. The whole bottom and right side of that board has clearly been running much too hot and I would test every component there before trusting it.

[jpaytoncfd]

Re: VX-922 PSU non cap part failures

You could easily use the new board if you replace the female conector on the second board with a male and use jumper wires. the new one you got looks like the one it mine. which has the LCD controler built into the LCD itself. It makes it very simple. so the male conector splits into the button wireing and goes into the LCD. However my transformer (c2) is blown and I cant find any info on what the values are. Does anyone know?

[boomer400]

Re: VX-922 PSU non cap part failures

Decided to update this thread so we could have some sort of conclusion. I ended up paying $25 dollars for a complete PS board which fits in correctly. I thought about doing what JPaytoncfd proposed as the connectors are basically the same. Wiring up a connector line wouldn't have been too difficult, just need to find the female pin blocks and a set of wires to bring them together. The problem is that I would have to hack up the rest of the case in order to make it all fit together and it wouldn't have worked well as the rear cover would have have to be seriously modified. In any event, the new board works fine and all is copacetic. It would be nice to find a transformer or 2 to fix the old board but.......I'm just too lazy right now. Plus, I have to fix 2 HP tablets and a bunch of desktop PSUs as well.

[MufasaDOG]

Re: VX-922 PSU non cap part failures

Hi guys
I have a VX 922 which I have replaced all the caps in the power supply but my problem is that when it came to connect the 4 small backlight plugs in I'm not sure which way round they go. I should've marked them I know but could someone please give me the correct way round they should go.
Thanks
Peter

[tom66]

Re: VX-922 PSU non cap part failures

Hi guys
I have a VX 922 which I have replaced all the caps in the power supply but my problem is that when it came to connect the 4 small backlight plugs in I'm not sure which way round they go. I should've marked them I know but could someone please give me the correct way round they should go.
Thanks
Peter

It's usually difficult to plug them in the wrong way - use that as a clue. You won't be able to plug the bottom-most bulb into the top connector for example. I'm don't think it matters at all which way they go around.

[Th3_uN1Qu3]

Re: VX-922 PSU non cap part failures

I'm don't think it matters at all which way they go around.

Correct.

[MufasaDOG]

Re: VX-922 PSU non cap part failures

Many thanks for your help on my question.
Cheers