Viewsonic E431S

[pacey]

Hi there, I've looked through the forum and found a couple of threads relating to issues with this monitor which seem the same as what I have, but they don't quite address my problem...

I have two of these Viewsonic Prolite E431S screens, both failing within a week of each other (had them 5 years and they both go at pretty much the same time?!) It's the usual 'screen is on but very, very dark' situation. I heard three definite pops or clicks when these went, maybe a second between each one, so I assumed three components blew in succession. The thing is, when I look at the boards in them there are no bulging or popped capacitors or any burn marks. I've never replaced these kind of parts before but wouldn't mind attempting it myself as I have nothing to lose (I've since bought a bigger monitor anyway), but I don't know *what* to replace. I was hoping for a trainwreck in there that I could work on but compared to the pictures other people have posted of the same LCD, mine looks fine.

Does anyone have any advice? Caps are cheap and I could fairly easily replace the lot of them, but it would be a bit of a waste of time.

Thanks if anyone can advise!
Pacey

[Krankshaft]

Re: Viewsonic E431S

Look for bubbles or bulges in SMD components. If you heard popping there has to be evidence somewhere.

Be sure to post some pics of both side of the board too.

[pacey]

Re: Viewsonic E431S

I don't see anything out of the ordinary, but then I'm not sure what to look for. I don't see any bulges or bungs popped out of underneath the caps...
:/

Are these pics clear enough? I can take some more of specific areas if needs be.

[Dgtech]

Re: Viewsonic E431S

With power applied, does this still click and pop? If so, try to listen for where on the board this sound is coming from (Safely). Also, If you could, please post the pics of the reverse (solder) side of the inverter board. Sometimes reflowing the solder on the transformers helps.

[pacey]

Re: Viewsonic E431S

No it didn't make any noises when power was applied, only when they first died. I'll get some pics of the reverse of the board tonight.
Thanks for the assistance!

[retiredcaps]

Re: Viewsonic E431S

I don't see anything out of the ordinary, but then I'm not sure what to look for. I don't see any bulges or bungs popped out of underneath the caps...

Check Q210, Q211 (and its partners). I can't make out the other ones, but if Q210 and Q211 are C5707, there is a possiblity they all 4 are shorted.

[Solder Boy]

Re: Viewsonic E431S

Don't forget to put your ears and nose to the top and or bottom of the monitor. The CCFL's might be shorting out too. If everything else seems to check out on the boards that's where I'd be looking next.

[pacey]

Re: Viewsonic E431S

Thanks for all the suggestions! The transistors are C5706, are they likely to be as bad as the 7's?

[retiredcaps]

Re: Viewsonic E431S

Thanks for all the suggestions! The transistors are C5706, are they likely to be as bad as the 7's?

Hmm, that was a pretty good guess on my part! Yes, c5706 are likely to be shorted as well. If they are shorted, you MUST resolder all the transformers leads on the backside otherwise they will possibly short out again.

Even if they are not shorted, resolder the transformer leads.

[pacey]

Re: Viewsonic E431S

Which make / model are suitable replacements for these transistors? I'll check the transistors tomorrow but it seems this is the most likely problem.
Will soldering the transformer leads mean taking it out of the circuit completely and resoldering it back in? Or just apply solder on each spot? (I've not had very much experience at this before!)

I still wonder what the three pops were though... I remember it was on the third pop that the screen went black.

[retiredcaps]

Re: Viewsonic E431S

Which make / model are suitable replacements for these transistors?

Will soldering the transformer leads mean taking it out of the circuit completely and resoldering it back in? Or just apply solder on each spot? (I've not had very much experience at this before!)

Checking the transistors is just one place to start. There are other components you can test. Like fuse, diodes, bridge rectifier, etc.

The C5707 are direct replacements for the C5706.

Doing a "proper" resoldering of the transformers means removing the old solder and using new solder. You don't have to remove the transformer.

Alternatively, you can add a bit of new solder onto the existing solder, but you risk creating poor/cold/dry solder joints.

[pacey]

Re: Viewsonic E431S

Good stuff, thanks. I'll let you know how I get on!

[pacey]

Re: Viewsonic E431S

Well I tested according to the info from this website: http://www.techlore.com/article/2673...k-Transistors/

On one board one pair of transistors seem to be ok, they have readings between '300' and '500'. On the other pair some pins are around '150' and a couple are at '1' or so.

On the other board, ALL pairs of transistors have wildly fluctuating figures - between '1' and '500', usually falling around '150'.

Can anyone decipher this for me? I feel as though 7 of the transistors are gone as only one has a fairly steady reading across all pins. Does this seem to point towards me replacing them all and resoldering the transformer as per retiredcaps suggestion?

Thanks again!

[retiredcaps]

Re: Viewsonic E431S

Well I tested according to the info from this website: http://www.techlore.com/article/2673...k-Transistors/

Try it this way ...

Here is how I would test a transistor.

1) set your multimeter on ohm - 200 ohms if you have a manual range
2) number the pins 1 to 3
3) put black on 1, red on 2 - record ohm
4) put black on 1, red on 3 - record ohm
5) put black on 2, red on 3 - record ohm

You should have 3 ohm readings.

If any transistor reads less than 2 or 3 ohms, you have a potential short.

Do same test as above, but with diode setting AND you want to reverse black and red.

1) put black on 1, red on 2 - record diode reading
2) put black on 1, red on 3 - record diode reading
3) put black on 2, red on 3 - record diode reading
4) put red on 1, black on 2 - record diode reading
5) put red on 1, black on 3 - record diode reading
6) put red on 2, black on 3 - record diode reading

You should have 6 diode readings.

[pacey]

Re: Viewsonic E431S

Thanks for the detailed reply! Ok so for one of the boards I get the following:

One pair:
Ohm = 0.2, 0.0, 0.2
Diode = 217, 2, 126, 126, 2, 217

Second pair:
Ohm = 0.4, 8.4, 8.0
Diode = 374, 539, 146, 374, 498, 499

I assume both sets of pairs should have a similar reading to each other but they clearly don't! I haven't done the other LCD as it will be the same fault. Culprits found you think?

[retiredcaps]

Re: Viewsonic E431S

Thanks for the detailed reply! Ok so for one of the boards I get the following:

One pair:
Ohm = 0.2, 0.0, 0.2
Diode = 217, 2, 126, 126, 2, 217

Second pair:
Ohm = 0.4, 8.4, 8.0
Diode = 374, 539, 146, 374, 498, 499

I assume both sets of pairs should have a similar reading to each other but they clearly don't! I haven't done the other LCD as it will be the same fault. Culprits found you think?

Can you post the make/model of your multimeter and perhaps a picture? In addition, where is your black probe plugged into?

The diode readings are not what I expected at all. It should be something like 0.355, 0.605 or 0L, not 499, 498.

All the ohms readings indicate that both transistors are shorted. I would desolder them and retest them again out of circuit using the ohms scale. This ensures that nothing in circuit is affecting the readings.

A good transistor when measured using ohms should be well over 1000 ohm.

[pacey]

Re: Viewsonic E431S

The unit is made by "Hilka" - no model number I can see and no idea where I got it from! The probes are attached inside the tester so they can't be plugged in wrong... meh, at least the ohm testing aspect seems ok!! I'll take the transistors out and test them again, but I'll probably get on and order some C5707's and replace the lot of them in the next few days anyway.

[retiredcaps]

Re: Viewsonic E431S

I'll take the transistors out and test them again, but I'll probably get on and order some C5707's and replace the lot of them in the next few days anyway.

When you do get the replacements, test them with your multimeter so you know what a "good" transistor before and after replacement looks like versus the bad.

[pacey]

Re: Viewsonic E431S

Will do. Thanks again for all your help to a newbie! I hope this will work!