viewsonic vx2835wm no power

[petersdrz]

This is my first post so I will try to give as much information as possible.
I have a viewsonic vx2835wm with no power, no lights, nothing, it has a phihong psm217-404-h-r power board (seems to be the same as a hanns-g hg281d). I have replaced all of the secondary cap (two where swollen) but no change. I have a constant 338v across the main primary cap. With the controll board unplugged I get 5v at 5v rail but nothing else, with the control board connected I get 3.2-3.6v at the 5v rail 9-10v at the 12v rail & 21-23v at the 24v rail all fluctuating.
not sure where to go from here

[PlainBill]

Re: viewsonic vx2835wm no power

This is my first post so I will try to give as much information as possible.
I have a viewsonic vx2835wm with no power, no lights, nothing, it has a phihong psm217-404-h-r power board (seems to be the same as a hanns-g hg281d). I have replaced all of the secondary cap (two where swollen) but no change. I have a constant 338v across the main primary cap. With the controll board unplugged I get 5v at 5v rail but nothing else, with the control board connected I get 3.2-3.6v at the 5v rail 9-10v at the 12v rail & 21-23v at the 24v rail all fluctuating.
not sure where to go from here
[

The first thing I can think of is what brand and series of caps did you use as replacements?

The second thing is there are a number of small (<100uF) caps on the primary side. Those should also be replaced.

The third thing is - excellent pictures.

And the last bit of advice - it's a minor problem when done the way you did it, but use 'Manage Attachments' below the text entry area to attach pictures.

PlainBill

[petersdrz]

Re: viewsonic vx2835wm no power

thanks for the reply
I've used a mixture of caps (all I can get from my local store) they are jamicon, suntan, samxon & ky they are all low esr 105 degree, I repair lots of smaller monitors & they have been ok in the past. I will try replacing all the small caps (but some may be a little harder to get, getting your hands on components in Australia is hard half the time I have to order them from the U.S or pay stupid prices from Australian distributors)

[pedro]

Re: viewsonic vx2835wm no power

thanks for the reply
I've used a mixture of caps (all I can get from my local store) they are jamicon, suntan, samxon & ky they are all low esr 105 degree, I repair lots of smaller monitors & they have been ok in the past. I will try replacing all the small caps (but some may be a little harder to get, getting your hands on components in Australia is hard half the time I have to order them from the U.S or pay stupid prices from Australian distributors)

G'day from the other side (I think) of Oz.

I have used Hitano low-ESR 105C caps exclusively on SMPS servicing for years with no comebacks. I originally went with that brand as (a) they had (decent) published specs, and (b) were carried by a reputable wholesale/commercial supplier here in Perth (X-on). Depending where you are located, WES in Sydney or X-on and Worldwide in Perth. X-on are geared to commercial customers but WES and Worldwide will sell in one-offs.

Whatever you do, don't let convenience cause you to use low-spec caps in a repair. Apart from the time and money you waste, it can mask the real fault.

[lucky13]

Re: viewsonic vx2835wm no power

It's probably a p/s. Sorry I have not been able to find a schematic.
OTOH, replace the 2 caps on the Main board C124 & C126. They've been know to mushrrom.

[steveoguy]

Re: viewsonic vx2835wm no power

This is my first post. I also have a Viewsonic VX2835WM LCD TV, checked all the caps in the SMPS, it stays in stsndby, & wo't start. I have a lot of this brand LCD TV, fix them, & they still won't come on. Have you guys had to replace the power supply, to get them running? Thanks.

[PlainBill]

Re: viewsonic vx2835wm no power

This is my first post. I also have a Viewsonic VX2835WM LCD TV, checked all the caps in the SMPS, it stays in stsndby, & wo't start. I have a lot of this brand LCD TV, fix them, & they still won't come on. Have you guys had to replace the power supply, to get them running? Thanks.

It should not be necessary to replace the power supply. It is not a trivial task to troubleshoot and repair them, but a methodical approach should be successful. The chief problem is a lack of any schematic; good pictures can make it possible to work around this problem.

Have you checked the voltage level at PSON on connector CN1 when the power LED on the monitor is on? When it is off?

PlainBill

[xsecret]

Re: viewsonic vx2835wm no power

My VX2835wm just failed today with the same issue (won't start).

I've ordered all the caps for the PSU. No bulging caps, but some discolored ones. I will change all of them and let you know if that solve the issue or not.

Anyway, C124 and C126 on the video board are both mushroomed.

[Shadows39]

Re: viewsonic vx2835wm no power

Hello.

Can someone tell me what capacitior is what i marked red?

I have viewsonic vx2835wm and power is PSM 217-404-h-r

I cant get this work and i think capacitior's is soldering a rong place...

[WolfBain]

Re: viewsonic vx2835wm no power

HI there,
Sorry. My first post, so please bear with me. I havent actually taken apart a monitor before as i normally do networking. Yet I have had a VX2835WM for a couple of years now & love it. But it sems this morning it it just wont start?
I have taken the power cable out & put it back In & also my pc cable yet the only thing that im getting is a slight crackling & then white flashing in the top right hand side of the monitor & then nothing.
When the Blue power light does come on, it stats no signal. flickers white again for a bit then dies.
I suppose it may seem a little green of me. But do you think I might be able to fix this myself. im quite capable of taking things apart? its the fixing & puting back I seem to get things wrong.. lol \
I have most equipement for doing the job I think as I have all my Networking gear. I suppose its just figuring what I need . Have read the thread & it makes a lot of sense so any other help would be appreciated.

Thanks for your help if you can.

Wolf (Terry)

[PlainBill]

Re: viewsonic vx2835wm no power

As I see it, you have three choices.

1. Put the monitor out by the curb and post a 'Curb Alert' on Craigslist. Go buy a new one.

2. Put the monitor in your closet and pretend you don't want to fix it.

HOWEVER, if you really want to fix it, have a DMM, camera, and soldering iron, there is a third option.

3. Take the monitor apart and post pictures (use 'Manage Attachments' - below the text entry area) of the entire back of the monitor (with the back removed) and another of the power supply. Someone nice (like retiredcaps) will look them over and make suggestions for tests to make.

The service manual is here.

PlainBill

[WolfBain]

Re: viewsonic vx2835wm no power

Thanks Bill, Will get onto it asap. *Thanks for the service manual also*
It's 4:50am here now & I think I should get some shut eye before starting my 1st Procedure.
Will do as you said & post the pictures here in this thread. hopefully will help others in the future with this problem.
I know for sure that I have Soldering iron & testing equipement. tbh, I dont really know how the tester works but we can get to that when I get the pics up.
Thanks for the quick replay & will be back on tomorrow hopefully with the pics.
What a way to spend the Holidays.. lol

Thanks again for all your help.

Talk soon

Terry

[retiredcaps]

Re: viewsonic vx2835wm no power

I dont really know how the tester works

If you mean multimeter, I can explain it in networking terms. Please post a picture of your multimeter as well so I know if it is manual or autoranging.

Think of a multimeter has a protocol analyzer. With a protocol analyzer (or sniffer), we typically mirror a port and direct the packets to the analyzer for analysis.

The multimeter is a very crude version of a protocol analyzer. With a multimeter, we probe different test points on the board. Just like moving a protocol analyzer to different parts of the network to capture areas we are interested in.

In networking, when we can't reach a host or destination, we use ping and traceroute to narrow down where the IP routing is broken. Same with a multimeter, we try to narrow down where the voltage has stopped.

Unlike traceroute, we have to manually move the multimeter along each point to figure out where the voltage has stopped.

With traceroute, everything is sequential. That is, we know the next IP hop. With the multimeter, we can take the same approach starting with the AC plug and moving forward. However, I will probably start in the middle and work forwards or backwards depending on the findings. This is divide and conquer. Much like trying to find a spanning tree loop in an ethernet network. Split the network into 2 and see where the loop occurs (I saw your introduction and reference to thinnet - I started with Arcnet).

PS. The oscilliscope is more like a protocol analyzer, but for 99% of the troubleshooting we do here, the multimeter is more than sufficient.

[WolfBain]

Re: viewsonic vx2835wm no power

Afternoon from the UK.

Have tried to upoad the pics I have which are well within the specs of attaching files & keep getting this error?
____________________________________________________________
Bad Request

Your browser sent a request that this server could not understand.
Apache/2.2.9 (Debian) PHP/5.2.6-1+lenny9 with Suhosin-Patch mod_ssl/2.2.9 OpenSSL/0.9.8g Server at srvcaps.badcaps.net Port 80
_____________________________________________________________

In regards to looking at the Monitor so far, Cant find any Caps that look mushroomed.
However have found 1 spot that looks to have darkened board around Q601.
The pic would show this but cant upload. lol
As I said, cant seem to see anything that really looks like it has blown or damaged? Has got me confused.

*Big thanks for the description on how to have my tester working. Cheers for that.. I now have a good idea on what it does..

Anyway. Till I can figure what to do next, im gonna rebuild it back up. Will give it a go to see if a clean & jiggering it about may have fixed it.

Other than that. Thanks guys for all your help & will be staying around & give you a heads up on what needs to be done when I can figure this upload prob im having. (*might be firefox - Will try GoogleChrome to see if it will fix it.*)

Talk soon.

Terry (Wolf)

[WolfBain]

Re: viewsonic vx2835wm no power

OK, Just a quick update.
Have cleaned it all & put everything back together. Hoping for a miracle......
Didnt Work.
Had the same thing as before so im a little stuck now. ** Talk Soon **

[retiredcaps]

Re: viewsonic vx2835wm no power

____________________________________________________________
Bad Request

Your browser sent a request that this server could not understand.
Apache/2.2.9 (Debian) PHP/5.2.6-1+lenny9 with Suhosin-Patch mod_ssl/2.2.9 OpenSSL/0.9.8g Server at srvcaps.badcaps.net Port 80
_____________________________________________________________

Here is a pic from the above post and it works fine. Again, pics must be 2000x2000 resolution and 2MB or less.

Start by posting a picture of your multimeter (cropped - close tight in). That should be way less than 2000x2000.

[rickdw]

Re: viewsonic vx2835wm no power

I had a slightly different issue with a friend's Viewsonic VX2835WM. It would just go tick...tick...tick. I advised him to buy a capacitor kit (I don't know where he got it from). He lost heart after replacing the two Caps on the video board thinking he was doing more damage than good. I replaced the others for him that were included in the kit from the power supply board. Only one of the caps removed tested bad, the 400V, 22uF. Putting it back togther, it worked ... sort of, but when it would go to powersave mode, the orange LED would start to flash rapidly and it wouldn't power up again until yuou pulled the power. I measured the +5 SB line and it was pulsing. I read somewhere on this forum to replace even the little caps. The kit he bought didn't include caps for C603 and C606, 10uF 50V and 1uF 100V. I removed and tested them, they were both bad. I found a couple in my bin that tested fine. Put those in and the monitor works well again. "Replace even the little ones" great advice from this forum, THANKS!

[Falcon99]

Re: viewsonic vx2835wm no power

Are you sure that C603 is a 10uF cap? From what i know it has 22 uF. But one can also find a 10 uF one close to there, it should be C406.

[Kennewb]

Re: viewsonic vx2835wm no power

I had simular problem with my vx2835wm and pulled it apart and found two caps that were bad on the video board. 470 uf 16V I replaced them and it worked like new. About a week later it was starting the same thing again. So I recaped the whole video board (main board) again it was working like new. Now it back to the same problem again. Upon reading the posts above I figure it's more to do with the power board so I will recap that board completly and hope for the best. I will let you know how it works or not once I'm done and give it a week..

[dossman]

Re: viewsonic vx2835wm no power

I'm working on a Viewsonic VS11257-1M I believe it is the 27" model. TV would not power on at all. I bought a cap replacement kit for the power supply because two 1500uf caps were swollen on the secondary side of the supply. After replacing the caps the TV still does not turn on. Will be testing voltages and looking at the mainboard to see if I can spot anything. Thanks Plainbill for the Service Manual link, although the troubleshooting is rather simplified it does show the board voltages.