ViewSonic VP201B problem

[tralala]

Hi badcaps guys. Thank you for the great forum.

Here is my first post. I apologize in advance; my English is not so strong and my electricity knowledge also.

I have two VP201B with identical problem.
When I turn monitor on I see black screen and after few second light goes to solid green.

I changed two PSU caps – 680uF, 25V; Inverter caps – 220uF, 25V; Resoldered the inverter's transformers. Checked all ribbon cables. Cleaned the logic board. Voltage from PSU is 17.8 V.
At the end I shortered the two fuses on inverter board.

Now when I turn monitor on he checks DVI, VGA I can see picture (i. e. Windows logo) for about 2 second then it goes black as in sleep mode. The light remains green.

What I'm missing?
Any help is greatly appreciated.

[uligli]

Re: ViewSonic VP201B problem

did u try the rgb?

[tralala]

Re: ViewSonic VP201B problem

I'm sorry. What do you mean with rgb.
Thanks

[uligli]

Re: ViewSonic VP201B problem

You're using DVI input, did you try the RGB (analog) input?

[tralala]

Re: ViewSonic VP201B problem

Yes, both DVI VGA gave me same thing. Picture for 1-2 seconds and then black screen and power solid green light ;(

[tralala]

Re: ViewSonic VP201B problem

Mistake: DVI, RGB input gave me same things.

BTW I didn't change the big fat guy on PSU units. I supposed if I have 18V from PSU all is good from there or I am wrong? And, Is the same voltage that came from logical board (18V) to inverter?

[PlainBill]

Re: ViewSonic VP201B problem

Yes, both DVI VGA gave me same thing. Picture for 1-2 seconds and then black screen and power solid green light ;(

This is a classic example of the 'two seconds to black' problem. It could be caused by an open or shorted transformer in the inverter, or a bad CCFL, or some bad wiring to the CCFLs.

PlainBill

[tralala]

Re: ViewSonic VP201B problem

I appreciate your response PlainBills. As I said I have two monitor with these problems.

"open or shorted transformer in the inverter" May I solve this with soldering iron?

or a bad CCFL, sorry but this sound for me as I need to change lamps on this units. I read on the forum that is not so easy and safety.

or some bad wiring to the CCFLs On two monitors at the same time?

[PlainBill]

Re: ViewSonic VP201B problem

I appreciate your response PlainBills. As I said I have two monitor with these problems.

"open or shorted transformer in the inverter" May I solve this with soldering iron?

or a bad CCFL, sorry but this sound for me as I need to change lamps on this units. I read on the forum that is not so easy and safety.

or some bad wiring to the CCFLs On two monitors at the same time?

Were you using them and they failed at the same time, or did you buy the two of them and discover they have the same problem? In the first case, it is very unlikely. In the second case, it sounds like someone had two monitors that failed with the same problem at different times; now he is getting rid of both of them.

PlainBill

[tralala]

Re: ViewSonic VP201B problem

One monitor goes dead and before I find your forum I just recycling it. For second and third they simply goes dead with same simptoms. Now I have two monitors with same errors at the begginig and I think will be stupid to trow them out (recycling) before ask the professionals.

I made my shot already I changed all caps. As I said I am not prof. Actually there is three "hot" components inverter, logic and PSU. I am ready to shot once again but with what, inverter or logic or..?

[PlainBill]

Re: ViewSonic VP201B problem

One monitor goes dead and before I find your forum I just recycling it. For second and third they simply goes dead with same simptoms. Now I have two monitors with same errors at the begginig and I think will be stupid to trow them out (recycling) before ask the professionals.

I made my shot already I changed all caps. As I said I am not prof. Actually there is three "hot" components inverter, logic and PSU. I am ready to shot once again but with what, inverter or logic or..?

I understand. And to answer your earlier question, monitors (and other electronics) often have common faults. So it isn't unusual to see several monitors with the same symptoms at the same time.

If the CCFLs on the VP201b are set up like the VP211b, the inverter return lines run along a metal channel, which gets rather warm. The wires often get overheated where they connect to the CCFL, and touch the metal channel. If they make contact the leakage current will trip the protection circuit on the inverter.

The first step is to read this thread. Take clear pictures of the front and back side of the inverter. I am particularly interested in the area around the transformers and the connectors to the CCFLs. Attach them to a post and I will try to guide you.

PlainBill

[tralala]

Re: ViewSonic VP201B problem

Sorry for the delay. Here is the pictures for both inverters.
Please let me know if these are ok or I need to look for other digital camera.

[PlainBill]

Re: ViewSonic VP201B problem

Sorry for the delay. Here is the pictures for both inverters.
Please let me know if these are ok or I need to look for other digital camera.

Thos pictures aren't OK, they are superb. My rule of thumb - if I can read the part number of the IC, it's great.

I've marked up the picture of the top side of the board. The points labeled R1, R2, etc are the return lines from the individual CCFLs. What you are going to have to do is measure the AC voltage from R1 to ground while the backlights are on. Observe all precautions for working on equipment while high voltage is present. It is best if you handle the probes and have someone else standing by to operate the power button on the monitor (and calling 911 if necessary).

With luck, the voltage on one pin will be significantly different than the rest.

PlainBill

[tralala]

Re: ViewSonic VP201B problem

Thanks PlainBill.
"measure the AC voltage from R1 to ground while the backlights are on"
This will be great challenge for me. I like this (and calling 911 if necessary)

Is there other thing I can do before measuring this? You mentioned "The wires often get overheated where they connect to the CCFL" may be I need to start with that. I am not sure how to remove the cover to see this but I will try.
And if the the wires are all OK just buy one inverter and try on both monitor with him.
And other stupid question: May I think the CCFL's are ok if I see picture on the screen even for 1 sec.

Please correct me if I am wrong.

[Krankshaft]

Re: ViewSonic VP201B problem

If one CCFL isn't firing at all on the display it won't be noticeable for the one second the screen is on.

By bridging the fuses you are risking further damage to the inverter. Luckily the PWM protection is kicking in. Try to keep inverter tests to a minimum until the faulty component is identified.

[tralala]

Re: ViewSonic VP201B problem

I disassembled totally one of the monitors. All wires from inverter to CCFLs seamed good. BTW there is no metal surface they passing by. All is plastic.
I swapped both inverters on this monitor and he gave me same thing. Picture for 1 sec. and.. darkness.

So the rest is to check the voltage from the inverter. Just to confirm, I start to measure the voltage from R1 with ground, then R2 to ground R3 to ground etc. One of them needs to be different then others, right?

[PlainBill]

Re: ViewSonic VP201B problem

I disassembled totally one of the monitors. All wires from inverter to CCFLs seamed good. BTW there is no metal surface they passing by. All is plastic.
I swapped both inverters on this monitor and he gave me same thing. Picture for 1 sec. and.. darkness.

So the rest is to check the voltage from the inverter. Just to confirm, I start to measure the voltage from R1 with ground, then R2 to ground R3 to ground etc. One of them needs to be different then others, right?

Not exactly. One MAY be different.

Short lecture on the backlight system: The backlight system consists of the controller, transformer drivers, transformers, CCFLs, and associated wiring.

The logic card (monitor controller) 'tells' the controller to turn on the backlight. Initially, the controller turns the CCFLs on at full brightness, then it reduces the drive and begins to monitor the system. If any fault occurs, it shuts down the CCFLs. Parameters that can be monitored include drive current to the transformers, voltage across the CCFLs, and current through the CCFLs. Usually, only a few parameters are monitored, typically, voltage across and current through the CCFLs.

Possible failures include voltage across the CCFL too high because of a bad (broken) tube or bad wiring; current through the CCFL too high because of an old CCFL, current too low because voltage was to low, etc. By measuring the voltage on the return lines from the CCFL we can see if the current on any CCFL is too high, or too low.

One other possible cause of the 'two seconds to black' problem is a failure in the monitoring circuits. Another is a shorted or open transformer.

PlainBill

[tralala]

Re: ViewSonic VP201B problem

Very clear explanation! Thanks a lot PlainBill

[bluto]

Re: ViewSonic VP201B problem

I just fixed another VP201b. The two small caps (22uf and 47uf) on the powersupply were faulty causing a no power on condition. I did a full re-cap while I had it apart. In doing so I created a 'two seconds to black' problem for myself. I managed to bend a pin over on both of the large ccfl connectors. After I accomplished this, the monitor started doing 'two seconds to black'. It took me a while to figure it out, but once I got the pins straightened again, it was back working fine.

So let this be a lesson to everyone to be very careful un-plugging and re-plugging the ccfl connectors.

I am posting a couple pictures because the inverter board looks slightly different than all other VP201b inverter boards on this forum. It has a single 'resistor' type fuse instead of smd fuses.

[HurricaneTech]

Re: ViewSonic VP201B problem

I have been having a similiar problem with a VP201b. When I turn the monitor on from the main power switch (by the plug) I get a quick flash of the green LED on the front and then nothing else.

I have 17.7 VDC from the PSU. Is this the correct output? I have the same voltage at pin 1 going to the Inverter board.

What else should I be checking?

BTW, my inverter board is the same as the one posted by Bluto.