MrFlibbles' Viewsonic VX2835WM Problem

[MrFlibble4747]

Re: MrFlibbles' Viewsonic VX2835WM Problem

PB in main board interconnected + small led switch panel board.

Reading at 5V SB is 3.6.

No light at switch board LED after pressing switch.

[retiredcaps]

Re: MrFlibbles' Viewsonic VX2835WM Problem

On the back of the power board, there is a solid white line. It separates the cold and hot side.

The hot side is the same side as the AC plug. The hot side can be up to 400V DC. The cold side is usually less than 24V DC.

Sometimes hot is referred to as primary and cold as secondary.

[retiredcaps]

Re: MrFlibbles' Viewsonic VX2835WM Problem

Reading 4.95. I guess this is good news so far.

Yes.

This is with PB disassembled from everything else, just screwed into the metal tray with the earth lead connected to the tray and the mains plug in.

Now plug in the main board (board with all the A/V inputs).

Recheck to make sure 5V SB is present and steady.

Post a picture of your main board so we can give more test points. If you are getting no power LED light, the problem likely lies in the main board.

Have to say I'm crapping myself as I'm not sure if I'm heading for an electric shock.

I was a newbie back in Apirl 2010 and know the exact feeling. Don't worry, the regulars here understand and give clear concise easy to understand instructions.

If you follow them exactly, the chances of you getting shocked are minimal, but not zero. We can't be held responsible for slip of the hand, drunkenness, inability to follow instructions, etc.

Everything I'm asking you to measure is "low" voltage. This is voltage less than 20V DC. If/when we ask you to measure "high" voltage, we will warn and say this is high voltage. High voltage can be close to 400V DC.

PS. Don't touch any of the heatsinks. They are most likely "live".

[MrFlibble4747]

Re: MrFlibbles' Viewsonic VX2835WM Problem

1) Set your multimeter to 20V DC. Plug in lcd and turn it on.

2) The most important voltage to look for right now is 5V SB.

3) Put your black probe on a ground screw that is closest to the 5V SB pin.

4) Put your red probe on the 5V SB pin.

5) Report your reading.

Reading 4.95. I guess this is good news so far.

This is with PB disassembled from everything else, just screwed into the metal tray with the earth lead connected to the tray and the mains plug in.

Have to say I'm crapping myself as I'm not sure if I'm heading for an electric shock.

Didn't get to this age with only one electric shock by being "adventurous"!

I'm not scared just risk averse! ;-)

[retiredcaps]

Re: MrFlibbles' Viewsonic VX2835WM Problem

1) Set your multimeter to 20V DC. Plug in lcd and turn it on.

2) The most important voltage to look for right now is 5V SB.

3) Put your black probe on a ground screw that is closest to the 5V SB pin.

4) Put your red probe on the 5V SB pin.

5) Report your reading.

[MrFlibble4747]

Re: MrFlibbles' Viewsonic VX2835WM Problem

Hi Again...

Current condition is dead as a doornail. No light, no action on power up.

Multimeter is DT830 3 1/2.

Gotta dash..hope this update hits the spot......

[retiredcaps]

Re: MrFlibbles' Viewsonic VX2835WM Problem

Then nothing at all. This progression took place over a couple of weeks.

You are going to need a multimeter to take some readings on the power board.

We want the DC voltages for CN1, CN2, and CN3. If there is a legend, please post a picture of it or list the values for each connector.

[selldoor]

Re: MrFlibbles' Viewsonic VX2835WM Problem

Hi- Thanks for the history- we now need to know exactly what it does now.
Start from not plugged in. Plug in - any lights sounds. If a light does it stay on
, flash, go off? Switch on - anything ? power light change? screen flash?
sound? - I have looked at the manual linked in the other post - doesnt have
much about the power supply - does yours? Can you post a close up pic of your
multimeter and advise the model number if its not clear in the pic.

Hmm much later edit surprised it let me- Have been looking at your pics and
As I believe you have already noticed part of the trace on U801 looks burnt.
Same goes for Q601 and U102 , resistor R119 looks dead. You should try and get the part numbers off these- may be the same as in other posts
Also around the burnt bits there is some glue type gunge this is mentioned in the following link
and you will need some rubbing alcohol to get it off.


http://www.fixya.com/support/t558401..._vx2835wm_turn

[MrFlibble4747]

Re: MrFlibbles' Viewsonic VX2835WM Problem

Hi and thanks for quick response.

Until it stopped working at all it always worked perfectly from cold start.
Problem developed from screen blanking out (possibly going into power saving mode) when not used for a while and being revived by unplugging and reconnection the power cord. Then blank screen with flickering in the background, power (blue) light flickering and going light blue or amber.
Then nothing at all. This progression took place over a couple of weeks.

Will get additional photo's tomorrow. I have 40W & 60W soldering irons and can do basic soldering. I have a multimeter but don't really know how to use it.

The maintenance manual has the schematics, let me know if you want it uploaded or if you have access to it.

The logic board looks perfect, no signs of problem components or "browned off" patches or tracks. I'll post pics of it tomorrow also.

Cheers,

[retiredcaps]

Re: MrFlibbles' Viewsonic VX2835WM Problem

The power board is probably the same as the problematic Hanns-G HG281D. There are not too many 28 inch monitors around and they all seem to utilize the same power board.

https://www.badcaps.net/forum/showthread.php?t=11329

If you search for this monitor and see a lot of threads on it. In one of those threads, I came to the conclusion that this monitor runs temperature hot and warrants a complete recap of the power and logic board.

And yes, tell us what is actually wrong with the monitor.

[selldoor]

Re: MrFlibbles' Viewsonic VX2835WM Problem

Hi - welcome to the forum. Pics are good - can you do one of the whole of the back of the board and if the connectors have any descriptive text (24v 12v 3.3v 5v gnd etc) close ups would be useful.
The other thing is you dont seem to actually say what is wrong? - did it go wrong suddenly or has it been flickering for a while, not alway coming on, starts dim and brightens, starts bright and dims etc.
You need to tell us exactly what happens when you switch on. Lights, sounds anything, nothing, flashing, continous.
In addition do you have a soldering iron - small bit-40watt. - can you use it? do you need to practice. Have you a multimeter/ voltmeter - can you use it have you got the instructions for it. - do you need to practice.
This IS the dummies guide - you can get all the guidance you need here but you need to be up for following instructions and doing the tricky work.
You will be advised what posts to read to help guide you.Any thing you can find that is relevant is great - use the search facility above.

[MrFlibble4747]

Just to "recap" from my new member post (pun intended)

Hi All, (names Dave by the way)

I'm in Perth Australia and have a knackered Viewsonic VX2835WM which displays all the classic signs (I have since discovered) of BAD CAPS! (Little B***ards!)

I'm halfway through dismantling the beast but could not see how to take it apart after getting the screws out (found service manual so can proceed).

I'm scared of the DIY electronics repair option but could be convinced if I can get the For the Dummies guide (need to explore posts more).
I'm still trying to establish if I'm still in warranty (3 years I hope).
I have a mental block when it comes to electronics even though I do a lot of DIY and messing around with wood/metal/computers.

Nice to find such an informative and helpful site.

NEW Stuff:
Monitor bought 4 years ago so no warranty.......
Have dismantled the beast thanks to the service manual and have examined boards and taken photo's.
The Power Board (PB) is definitely "browned off" with signs of heat damage on RHS of board particularly on the surface mount component side of the board with brown patches showing through onto the hardware side. Heat concentration appears to be around component ID's ZD702 top-middle front, ZD406 top-middle rear and C114 bottom-middle front and Q601 bottom-middle rear of PB.
Caps look OK to me (but what do I know) no sign of Cap Poop, bulging etc unless I missed something.
Could be general PB fried/blown fuse rather than caps perhaps (but what do I know).

Over to the guru's with thanks for any feedback.

Cheers (time for a beer, 36 deg C here today.........)

PS I think someone else posted VX2835 PB pics that matched mine almost exactly for the burn marks.