viewsonic vx2835wm no power

[Lumberjack777]

Re: viewsonic vx2835wm no power

@Lumberjack777, so what DC voltage do you get at the main cap when it is on?

I'm sorry budm; I was on vacation. I put in the news caps, and put it back together and it worked. The recycle center already sold it. Sorry.
It sounds like badcapass got a power supply that had been formerly "fixed" and they used improper caps. That may have taken out some other component. You are 100 times better at diagnosis than I am. Maybe you or retiredcaps or somebody can help him with those diagnostics. He also has a spare good power supply if needed. Happy 4th!

[badcapass]

Re: viewsonic vx2835wm no power

Hi,

replaced almost all caps on the main board, wasn't funny...
What I did:

Nr.	[muF]	[V]	done
C8	10	16	-
C13	10	16	-
C14	10	16	-
C18	10	50	x
C19	10	16	x
C60	10	16	x
C61	10	16	x
C63	-	-	-
C69	100	16	x
C74	10	10	x
C77	10	16	x
C80	100	16	x
C83	100	16	x
C92	10	16	x
C94	100	16	x
C97	100	16	x
C98	470	16	x
C99	470	16	x
C103	470	16	x
C119	10	16	-
C120	10	16	-

And yes, nothing changed. I hope I didn't distroy the main board. But now back to power supply. If I had known how to power it on by connecting SBV+5 to PSON, maybe I would have fixed it already.

status of the power supply:

issue   standby / "on"
C3      320V / 318V
blue LED    off / off
Q202 pin i/1 1V  / ~1V
Q202 pin i/2 0V  / 0V
Q202 pin i/3 0V  / 0,4V
Q601 pin i/1 20V / ~0,3V
Q601 pin i/2 0V  / 0V
Q601 pin i/3 22V / ~1V

It reacts on power on, but not in the right way...
I hope you have any hint and when it would be to let it die.

Regard
Paul

[badcapass]

Re: viewsonic vx2835wm no power

Edit: blue LED is still alive, just the cable was unplugged...

[badcapass]

Re: viewsonic vx2835wm no power

Hi,

just replaced the power supply, since my other HG281D shows a picture with lots of stripes and shadows (getting hot here). So I took the power supply an put it in my "new" still not working one. The fixed main board and all the rest works like a charme! Right colors, clear picture, no dead pixel. Now it's time to recap the next main board and getting the power supply fixed or replaced. If both would have the same power supply, it would be a lot easier... I will buy another one on ebay, since shipping for the power supply from china costs more then another used HG281D.

Regards and thanks for your input.
Paul

[yeahz]

Re: viewsonic vx2835wm no power

Hello, for presentation, i'm a computer enthousiast but not much of an expert

I have a Viewsonic VX2835W, and it has been misbehaving recently. Sometimes the power goes off and does not go on until i unplug and replug it several times.

Thanks to all of you I know that i need to replace 124 and 126 on the video unit , but on the power unit I seem to have a burnt component, (not sure what it is though)
I have taken pictures for you to see.

I would appreciate if an "expert" could tell me if i need to replace the whole power unit or just that component.
Cheers!



Tom

[budm]

Re: viewsonic vx2835wm no power

It looks like flux, try cleaning it with Alcohol. Did you test those components with the meter?

[yeahz]

Re: viewsonic vx2835wm no power

I have NO idea how to start to test these components (my ee classes are far! ) what boggles me is how to test components without taking them out of the system.

Okay I have cleaned the residue, that smelled like burnt something, I had to scratch it with a blunt object, I haved posted a pic.

I have a multimeter of course and i know how to use it but is this component a transistor..? (strange that the middle pin does not seem connected to any circuitry..) and right above it , right newt to the small cap it says: CAUTION: DANGEROUS VOLTAGE!

[Rtech]

Re: viewsonic vx2835wm no power

It looks as though it is a standard type of component, where the TAb at the top is internally connected to the short middle pin,and therefore the pin is not connected as it is not necessary. You can confirm that is the case by using the meter.

[yeahz]

Re: viewsonic vx2835wm no power

Rtech: you were right.

Budm: If it was flux, would alcohol have gotten rid of it?(without need for scratching)

[budm]

Re: viewsonic vx2835wm no power

I use alcohol and brush.

[yeahz]

Re: viewsonic vx2835wm no power

I see,
and according to you, that flux was residue present from the time of manufacturing? Or was it there after some overheating (which i supposed to be the case)?

[tehtronics]

Re: viewsonic vx2835wm no power

I need the schematic PSM217-404-H-R. Can you help me?

[banem]

Re: viewsonic vx2835wm no power

I would appreciate if an "expert" could tell me if i need to replace the whole power unit or just that component.
Cheers!



Tom

A bit late reply, but mostly for other who thinks the issue is this transistor - it is not! On all boards it looks like burnt and like someone re-solder it. In fact it has more solder applied and it is getting hot while working - its normal. That part do not have to be replaced unless it is broken.

How did I fix my vx2835 is here - I put it there since it has the same power board as Viewsonic. 5 caps replaced.

[hamada13]

Re: viewsonic vx2835wm no power

replace voltage regulator in main board if not work replace the crystal