vp2130b cap help

[retiredcaps]

Re: vp2130b cap help

Hissing sound indicates a problem with the CCFLs, either a bad solder connection, or arcing through the insulation.

budm has good photos of the above at

http://s807.photobucket.com/albums/y...klight%20lamp/

[zaphar]

Re: vp2130b cap help

Hissing sound indicates a problem with the CCFLs, either a bad solder connection, or arcing through the insulation.

PlainBill

I'm going to take a look at the CCFLs, however, it seems odd that if I unplug one of the CCFLs the other one doesn't hiss, and vise versa. The hissing only happens when both are plugged in.

If that checks out OK, I'm going to check the power supply voltage after I figure out a safe way to do it.

[zaphar]

Re: vp2130b cap help

Alright, I just disassembled everything and the CCFLs look to be good. I have removed them from the assembly and plugged them back into the inverter. When turning on the monitor, they light up as expected for one second, then turn off. The hissing sound seems to be originating from the transformers on the inverter. I have also observed that if I keep turning the monitor on and off (using front power button), the period of hissing decreases and the lights stay on longer before turning off. It eventually gets to the point where little to no hiss is produced and the lights stay on till they auto shut off and the power LED turns orange.

[alexanna]

Re: vp2130b cap help

You say the ccfls look ok. Is there any indication of discoloring on the return wires where they attach to the ccfls?
Al.

[zaphar]

Re: vp2130b cap help

Well, I don't know how it did it, but after taking the LCD apart, reassembling it, and turning it on and off tens of times, the monitor seems to be functioning properly. The long hissing sound at start up isn't made and I'm actually using the monitor right now to type this message. If I have any problems I'll check back in. Thank you for your help and useful information, this thread will be a valuable resource for anyone with one of these monitors as they're all doomed to get the plague sooner or later.

[retiredcaps]

Re: vp2130b cap help

Well, I don't know how it did it, but after taking the LCD apart, reassembling it, and turning it on and off tens of times, the monitor seems to be functioning properly.

I had that happen to me once. I had 2 seconds to black and did everything I could. I even had a spare ccfl and could not find the problem. Finally, I took them out for inspection and could not find anything wrong.

I was surprised when the monitor work and used it for about 2 weeks straight with no problems.

My guess is that when I removed the ccfl, the wiring may have been pinched or intermittment. By removing the ccfl, I may have unpinched the internal wiring?

[alexanna]

Re: vp2130b cap help

You say the ccfls look ok. Is there any indication of discoloring on the return wires where they attach to the ccfls?
Al.

What I am finding,
Ccfls return wires for some reason are deteriorating where they are soldered to the ccfl tube, and they are just barely making contact with very few strands of wire holding them on. Heat has to have a great affect
If you test these after you have removed them from the panel most of the time they will light normally and the 2 second to black may not occur, You may or may not see dark areas at the end of the ccfl tube.
Usually you will see some indication on the wire where it attaches to the ccfl tube.
I use a toothpick to unstick the return wire from the ccfl channel, and then give it a gentle tug if it's bad
Well you can tell very quickly
Al.

[zaphar]

Re: vp2130b cap help

I spoke to soon, the monitor is back to the way it was when I first aquired it, 2 seconds to black with glimps of desktop. The hissing sound is definitely originating from the transformers on the inverter. I'll take it apart again and inspect the CCFTs more closely at the ends. Is there any explenation as to why the hissing only occures if both CCFTs are plugged into the inverter but not when only one is?

[zaphar]

Re: vp2130b cap help

What I am finding,
Ccfls return wires for some reason are deteriorating where they are soldered to the ccfl tube, and they are just barely making contact with very few strands of wire holding them on. Heat has to have a great affect
If you test these after you have removed them from the panel most of the time they will light normally and the 2 second to black may not occur, You may or may not see dark areas at the end of the ccfl tube.
Usually you will see some indication on the wire where it attaches to the ccfl tube.
I use a toothpick to unstick the return wire from the ccfl channel, and then give it a gentle tug if it's bad
Well you can tell very quickly
Al.

Alright, it looks like the CCFLs have issues. After closer inspection and the tug test you mentioned, the wires do appear to be crispy and one wire did brake free. The tubes look to be in good shape (what I checked before). So I guess I'll replace some of the wire and resolder. Thanks again for your help.

[alexanna]

Re: vp2130b cap help

Alright, it looks like the CCFLs have issues. After closer inspection and the tug test you mentioned, the wires do appear to be crispy and one wire did brake free. The tubes look to be in good shape (what I checked before). So I guess I'll replace some of the wire and resolder. Thanks again for your help.

That is a very good example,Depending on the position or the kapton tape it could easily be missed.Your ccfls are probaly ok.After repairing the solder, assemble every thing except the dark LCD and let it run to thoroughly warm up.
Al.

[retiredcaps]

Re: vp2130b cap help

Is there any explenation as to why the hissing only occures if both CCFTs are plugged into the inverter but not when only one is?

Just a guess here.

It may possible that when two ccfls are plugged in, the bad ccfl (or wiring) draws more and more power causing the hissing.

When one is unplugged the inverter pwm chip detects a OLP (open lamp protection). It then quickly (usually 2 seconds or less) shuts down the ccfls. Since the ccfls are shutdown, there may not be enough time for you to hear the hissing.

[alexanna]

Re: vp2130b cap help

Just a guess here.

It may possible that when two ccfls are plugged in, the bad ccfl (or wiring) draws more and more power causing the hissing.

When one is unplugged the inverter pwm chip detects a OLP (open lamp protection). It then quickly (usually 2 seconds or less) shuts down the ccfls. Since the ccfls are shutdown, there may not be enough time for you to hear the hissing.

I really wish I knew the exact answer, the only thing I can relate it to is the secondary ignition system of an automobile. Any added resistance to the secondary circuit will induce higher voltage to try to overcome the added resistance, the more voltage available will increase the amperage assuming the resistance stays the same, and cause more strain on the coil.And evently the OVP kicks in.
This is just my theory, but I do not have a strong understanding of the inverter circuits that use an AC voltage source to be sure if it's a possibility
I always hope someone will correct me if I am totally out in left field.
Al.

[PlainBill]

Re: vp2130b cap help

I really wish I knew the exact answer, the only thing I can relate it to is the secondary ignition system of an automobile. Any added resistance to the secondary circuit will induce higher voltage to try to overcome the added resistance, the more voltage available will increase the amperage assuming the resistance stays the same, and cause more strain on the coil.And evently the OVP kicks in.
This is just my theory, but I do not have a strong understanding of the inverter circuits that use an AC voltage source to be sure if it's a possibility
I always hope someone will correct me if I am totally out in left field.
Al.

You aren't too far off base with your analogy, but there are a couple of essential differences.

The technical description of a CCFL inverter is a constant current AC source with protection. The way this is implemented varies, and can cause headaches. In general, most 'typical application' designs found in datasheets show a single CCFL. When multiple CCFLs are are used some designers go for an approach where they measure the total current through the CCFLs and adjust the drive to keep that constant. Others measure the current through a single CCFL and assume the others will be drawing the same current. This can cause problems as the CCFLs age.

Protection designs vary. The best approach will monitor the peak voltage across each CCFL and shut down if it goes too high (OVP). A good design will also monitor the current through each CCFL and shut down if the current through any CCFL goes too high (OCP). Cheap designs will skip the OVP and shut down if the current through a lamp is too low.

The sample is too small, but it appears the biggest faults are bad capacitors, wiring problems, and broken or old CCFLs coming next, then transformer problems. The hardest problem to isolate is a defective component in the protection circuit.

The chief difference between the automobile ignition system and an inverter is the ignition system puts out a fixed amount of energy, the voltage and current are dictated by the condition of the spark plugs and wiring, mixture, etc. The inverter actively controls the current and limits the voltage.

PlainBill

[alexanna]

Re: vp2130b cap help

Thanks PlainBill for the explanation,
This monitor stuff is habit forming for me. I really wish I would have pursued a career in electricity/electronics rather than automotive 40 years ago, I know I would have less problems with my back and knees ,But I was never out of a job until I couldn't do it any more .
Al.

[zaphar]

Re: vp2130b cap help

I'd also like to thank you for the explanation. It's important to understand how things work in addition to getting things to work.

[PlainBill]

Re: vp2130b cap help

I'd also like to thank you for the explanation. It's important to understand how things work in addition to getting things to work.

It requires a balance. Certainly ignoring several bulging caps while trying to solve a 'two seconds to black' problem by studying the operation of the inverter isn't real productive. On the other hand, replacing each component in the inverter until the problem is solved isn't very efficient either.

Years ago I was lead technician in a production test facility. Most of the techs working under me would quickly check a board for common problems - sometimes before even testing it. Certainly if a board failed a certain test they would rely on experience and known common flaws for that failure.

One of the tech sneered at that approach, calling them 'eye techs'. He insisted the best way was to understand the complete circuit, so in case of a failure it would be possible to isolate the cause quickly. When you have a board with a couple of dozen ICs, that is no easy task.

The supervisor explained how he did it when he worked as a technician. He started by following the test procedure until there was a failure. Then he would look for the obvious problems - solder shorts, missing components, ICs not inserted properly. If he couldn't fix it in 10 minutes he would label it with the step that failed and set it aside. Usually by lunchtime he had met the productivity standards for a full day.

After lunch he would take a board that represented the most common failure, analyze the circuit, and identify the failure. Usually this involved nothing more complicated than following the signal through the various ICs. Once he had identified the failing component he checked all the other boards with the same failure, and had them repaired if the cause was the same. Then it was retest, and another big bunch of boards done.

Typically, his day's productivity was double anyone else's. His reward was being promoted to lead technician, where he taught other technicians how to boost their productivity while working less.

I labeled the process 'Work smarter, not harder.'

PlainBill

[JimHorn]

Re: vp2130b cap help

Just a quick note - replaced the fuses on my VP201 and the caps in a VP2030b and they're both working great. Many thanks to all - these were thrown out at work and will be a great help at home!

[zaphar]

Re: vp2130b cap help

Unfortunately, my problems are not over. In my original attempt at fixing this monitor, I used some out of spec caps and recently replaced them with the right ones. At this point, the monitor now has a working backlight system, but only if I unplug the LCD module to main board connection.

If the LCD module is plugged in, I get the standard 2 seconds to black issue (working LCD module via flashlight test; from cold start, desktop may not even show on LCD, but will after a few power on/off cycles)
If the LCD module is unplugged, the monitor functions as normal minus working LCD module (green light, backlight on ==> goes into standby mode: amber light and backlight turns off).

I used my multimeter to see what was going on with the connections from the power supply board to the inverter. There's 8 pins that enter the inverter, three are 20VDC, three are ground, one is on/off (according to inverter IC datasheet anything below 0.7VDC is off and above that is on), and one is brightness adjust.

When checking values, the following was noted:
-When monitor is turned on via button the on/off pin goes from 0VDC to 3.3VDC and stays that way until it is turned off via button, no fluctuations.
-The adjust pin reads: 4.5VDC when monitor is powered but not turned on, 0.2VDC when monitor is turned on via button and desktop shows on screen, 1.5VDC when backlights shut off after a second or two.
-The 20VDC pins are: stated voltage when monitor is powered but not turned on, 20.2VDC when monitor is turned on via button but before desktop shows, 19.4VDC when desktop shows, 20.2VDC when backlight turns off after a second or two.

(It may also be useful to know that the adjust and on/off pins do not interact with any components on the power board and are routed directly to the connector that bridges power board to main board.)

I have also (due to assembling/disassembling many times) partially detached one of the flex PCBs that connects the LCD screen to the LCD driver (which is a part of the LCD module). Is this possible to fix and if so what's the best way to go about doing so (I've never done it before)? Thanks in advance for any help provided.

[jetadm123]

Re: vp2130b cap help

I have also (due to assembling/disassembling many times) partially detached one of the flex PCBs that connects the LCD screen to the LCD driver (which is a part of the LCD module). Is this possible to fix and if so what's the best way to go about doing so (I've never done it before)? Thanks in advance for any help provided.

Bad news. I don't think you're going to be able to re-attach that flex ribbon cable back to the LCD panel. That connection is done by the LCD manufacturer using special equiptment.

[zaphar]

Re: vp2130b cap help

Hmm, oh well, I guess it was a good project while it lasted. On closer inspection it looks like the traces where ripped off so it's a goner. I guess I'll cannibalize it for parts.