IBM 6734-ABO Not working.

[Welchs101]

Hi,

I have an IBM 6734-ABO which is not working.

Problem description:
I power up the monitor and green led comes on but there is no image on the screen.


What i have done thus far:
1-Shined flashlight on screen and i can see a faint image on the screen.

2-Measured voltages at connector (see enclosed pic of connector):
Pin1=>17v
Pin2=>17V
Pin3=>0.006V
Pin4=>0.006V
Pin5=>0.006V
Pin6=>5.11V
Pin7=>5.11V
Pin8=>0.038V
Pin9=>4.6V

Note: According to the writing near the connector the 17V reading should be 13V. Is this a problem?


3-Re-soldered transformer leads. This did not fix the problem.

4-Replaced a few capacitors on the power/inverter board shown as A,B and C.

5-I checked the 4 bulbs using my home-made bulb checker. All 4 bulbs seemed to be "ok".


At this point i would normally just replace "all" the caps on the board but in this case there are a few caps on the board that i dont have so replacing all of them would have to wait until after i order parts. I woud rather not do this unless i have to.

Any one have any suggestions on what to do to figure out the problem?

[PlainBill]

Re: IBM 6734-ABO Not working.

Hi,

I have an IBM 6734-ABO which is not working.

Problem description:
I power up the monitor and green led comes on but there is no image on the screen.


What i have done thus far:
1-Shined flashlight on screen and i can see a faint image on the screen.

2-Measured voltages at connector (see enclosed pic of connector):
Pin1=>17v
Pin2=>17V
Pin3=>0.006V
Pin4=>0.006V
Pin5=>0.006V
Pin6=>5.11V
Pin7=>5.11V
Pin8=>0.038V
Pin9=>4.6V

Note: According to the writing near the connector the 17V reading should be 13V. Is this a problem?


3-Re-soldered transformer leads. This did not fix the problem.

4-Replaced a few capacitors on the power/inverter board shown as A,B and C.

5-I checked the 4 bulbs using my home-made bulb checker. All 4 bulbs seemed to be "ok".


At this point i would normally just replace "all" the caps on the board but in this case there are a few caps on the board that i dont have so replacing all of them would have to wait until after i order parts. I woud rather not do this unless i have to.

Any one have any suggestions on what to do to figure out the problem?

Is there any sign at all of the CCFLs flashing when the power button is 'cycled'? If not, trace the 13 volt line to the inverter and make sure there are no blown fuses. Check the two inverter driver ICs for shorts. Check the Backlight 'on' signal to see if it gets all the way to the inverter controller.

My reasoning: 'Two seconds to black' issues indicate the inverter is working, it's shutting down because a fault was detected. 'No backlights' issues are a case of the inverter not working at all, either because it does not have power, or because the 'On' signal is not getting through.

PlainBill

[Welchs101]

Re: IBM 6734-ABO Not working.

When i cycle the power button you cant see any sign of the ccfl's coming on from the front screen. However, if you look at the back of the screen you can see the ccfl coming on for just a micro-second.

I have looked for fuses, other than the fuse near where the power comes in, but i cant find any.

Is the 17V high.......could this be a sign of where the problem is located?

[PlainBill]

Re: IBM 6734-ABO Not working.

When i cycle the power button you cant see any sign of the ccfl's coming on from the front screen. However, if you look at the back of the screen you can see the ccfl coming on for just a micro-second.

I have looked for fuses, other than the fuse near where the power comes in, but i cant find any.

Is the 17V high.......could this be a sign of where the problem is located?

The fact that there is a flash, even a brief one says it is NOT blown fuse of other power issue. Remember, If it works even for a fraction of a second, it's a 'two second (OK 200 microsecond) to black issue.

The 17 Volts MIGHT be a problem, but it is more likely that it is a symptom. The SMPS regulates the 5 Volt supply very carefully. The 12 volt (or 13 in this case) varies by load. And with the inverter shut down, there isn't any load.

This is the same search game we did on another inverter, made more difficult by the very short 'on' time. The first step - compare the resistances of the secondaries of the inverter transformers.

PlainBill

[Welchs101]

Re: IBM 6734-ABO Not working.

I measured the resistances between the transformers:

Transformer A: (1 to 2....red lead on 1 and black lead on 2)
1 to 2, 1 to 3, 1 to 4, 1 to 5, 1 to 6, 1 to 7, 1 to 8, 1 to 9
0.3ohm,Open, Open, 0.3ohm, 0.3ohm, Open, Open, Open

2 to 3, 2 to 4, 2 to 5, 2 to 6, 2 to 7, 2 to 8, 2 to 9
Open, Open, 0.3ohm, 0.2ohm, Open, Open, Open

3 to 4, 3 to 5, 3 to 6, 3 to 7, 3 to 8, 3 to 9
0.2ohm, Open, Open, Open, Open, Open

4 to 5, 4 to 6, 4 to 7, 4 to 8, 4 to 9
Open, Open, Open, Open, Open

5 to 6, 5 to 7, 5 to 8, 5 to 9
0.2ohm, Open, Open, Open

6 to 7, 6 to 8, 6 to 9
Open, Open, Open

7 to 8, 7 to 9
Open, 1081ohm

8 to 9
Open



Transformer B: (1 to 2....red lead on 1 and black lead on 2)
1 to 2, 1 to 3, 1 to 4, 1 to 5, 1 to 6, 1 to 7, 1 to 8, 1 to 9
0.2ohm, Open, Open, 0.3ohm, 0.3ohm, Open, Open, Open

2 to 3, 2 to 4, 2 to 5, 2 to 6, 2 to 7, 2 to 8, 2 to 9
Open, Open, 0.3ohm, 0.3ohm, Open, Open, Open

3 to 4, 3 to 5, 3 to 6, 3 to 7, 3 to 8, 3 to 9
0.2ohm, Open, Open, Open, Open, Open

4 to 5, 4 to 6, 4 to 7, 4 to 8, 4 to 9
Open, Open, Open, Open, Open

5 to 6, 5 to 7, 5 to 8, 5 to 9
0.2ohm, Open, Open, Open

6 to 7, 6 to 8, 6 to 9
Open, Open, Open

7 to 8, 7 to 9
Open, 1091ohm

8 to 9
Open






I also measured the mosfets (see pic AP4501M). The data sheet for the mosfets can be found at this link:
http://pdf1.alldatasheet.com/datashe...R/AP4501M.html

Note: For the mosfets the Drains 1 and 2 are all shorted together.

Note: All the measurements from drain to source or drain to gate are "opens" or really high resistance.

[PlainBill]

Re: IBM 6734-ABO Not working.

I measured the resistances between the transformers:

Transformer A: (1 to 2....red lead on 1 and black lead on 2)
1 to 2, 1 to 3, 1 to 4, 1 to 5, 1 to 6, 1 to 7, 1 to 8, 1 to 9
0.3ohm,Open, Open, 0.3ohm, 0.3ohm, Open, Open, Open

2 to 3, 2 to 4, 2 to 5, 2 to 6, 2 to 7, 2 to 8, 2 to 9
Open, Open, 0.3ohm, 0.2ohm, Open, Open, Open

3 to 4, 3 to 5, 3 to 6, 3 to 7, 3 to 8, 3 to 9
0.2ohm, Open, Open, Open, Open, Open

4 to 5, 4 to 6, 4 to 7, 4 to 8, 4 to 9
Open, Open, Open, Open, Open

5 to 6, 5 to 7, 5 to 8, 5 to 9
0.2ohm, Open, Open, Open

6 to 7, 6 to 8, 6 to 9
Open, Open, Open

7 to 8, 7 to 9
Open, 1081ohm

8 to 9
Open



Transformer B: (1 to 2....red lead on 1 and black lead on 2)
1 to 2, 1 to 3, 1 to 4, 1 to 5, 1 to 6, 1 to 7, 1 to 8, 1 to 9
0.2ohm, Open, Open, 0.3ohm, 0.3ohm, Open, Open, Open

2 to 3, 2 to 4, 2 to 5, 2 to 6, 2 to 7, 2 to 8, 2 to 9
Open, Open, 0.3ohm, 0.3ohm, Open, Open, Open

3 to 4, 3 to 5, 3 to 6, 3 to 7, 3 to 8, 3 to 9
0.2ohm, Open, Open, Open, Open, Open

4 to 5, 4 to 6, 4 to 7, 4 to 8, 4 to 9
Open, Open, Open, Open, Open

5 to 6, 5 to 7, 5 to 8, 5 to 9
0.2ohm, Open, Open, Open

6 to 7, 6 to 8, 6 to 9
Open, Open, Open

7 to 8, 7 to 9
Open, 1091ohm

8 to 9
Open






I also measured the mosfets (see pic AP4501M). The data sheet for the mosfets can be found at this link:
http://pdf1.alldatasheet.com/datashe...R/AP4501M.html

Note: For the mosfets the Drains 1 and 2 are all shorted together.

Note: All the measurements from drain to source or drain to gate are "opens" or really high resistance.

OK, simplifying this, on the primary side we have 1-2-5-6 and 3-4 all reading under one ohm for both transformers. On the secondary side we have 7-9 reading 1081 to 1091 ohms on the two transformers. This is pretty close, and doesn't constitute a 'smoking gun'.

Do you have a spare CCFL you can use to check each output? Use it as a substitute for each of the CCFLs in the monitor one at a time. What we are hoping for is a difference in brightness in one or two positions.

PlainBill

[Welchs101]

Re: IBM 6734-ABO Not working.

The spare ccfl i have is "in another monitor". I use another monitor to check the "bulbs" of the monitor that is "broken". I can try to use this but since the bulb is "enclosed" i may not see much.

How would i hook this up? The broken monitor has 4 bulbs. So would i leave 3 of the bulbs connected, disconnect one of the 4, use one of the bulbs from my "tester"........do this same thing for the other 3 bulbs from the monitor that is "not working".........is this what you want tme to do? Not sure what this tells me?

Again, the bulbs from the broken monitor appear to be working fine.

[PlainBill]

Re: IBM 6734-ABO Not working.

The spare ccfl i have is "in another monitor". I use another monitor to check the "bulbs" of the monitor that is "broken". I can try to use this but since the bulb is "enclosed" i may not see much.

How would i hook this up? The broken monitor has 4 bulbs. So would i leave 3 of the bulbs connected, disconnect one of the 4, use one of the bulbs from my "tester"........do this same thing for the other 3 bulbs from the monitor that is "not working".........is this what you want tme to do? Not sure what this tells me?

Again, the bulbs from the broken monitor appear to be working fine.

Exactly what I was trying to describe.

Recall this is actually a case of 'two seconds to black', but the interval may be more like .2 seconds. Possible causes are a bad CCFL (you have eliminated this), insufficient voltage to light a CCFL, or a fault in the sensing circuit. Troubleshooting the sensing circuit will be a bear, the on time is so short you won't be able to make a reading. So let's make sure all outputs to the CCFLs are putting out the same voltage. If two outputs light a test CCFL to full brightness, while two don't actually light it, we know it's an output problem. If all are equal brightness, we then figure out how to troubleshoot the sensing circuit.

To that end, what is the part number of the inverter controller?

PlainBill

[Welchs101]

Re: IBM 6734-ABO Not working.

When you ask "what is the part number of the inverter controller"......i am not sure what your asking for.

ARe you asking for the part number of the "pcb board" or something else.

Also, one question on the process of using another bulb to help diagnose the problem. If the lamp only comes on for 0.2 seconds........how am i going to distinguish between the different bulbs........that might be kinda hard. I do recall you having me measure voltages at the bulbs one time....would this be better?

[PlainBill]

Re: IBM 6734-ABO Not working.

When you ask "what is the part number of the inverter controller"......i am not sure what your asking for.

ARe you asking for the part number of the "pcb board" or something else.

I was asking for the part number of U301 - the 20 pin IC that is the inverter controller. It's a BIT3105, by the way. What's the point in asking for pictures if I don't look at them?

Also, one question on the process of using another bulb to help diagnose the problem. If the lamp only comes on for 0.2 seconds........how am i going to distinguish between the different bulbs........that might be kinda hard. I do recall you having me measure voltages at the bulbs one time....would this be better?

Let me explain this carefully. You take a bare CCFL with a matching connector. All four of the original CCFLs are hooked up to the inverter. You unplug the one in the upper left corner and plug in the test CCFL. You hit the power button on the monitor, the lamp flashes with the intensity of a camera flash. We'll call that an '8'. (A '9' you wouldn't have any eyelashes; we won't even think about what a '10' would be like). You unplug the test CCFL, plug the original CCFL back in. You unplug the original CCFL in the upper center, and plug the test CCFL in. Again you hit the power button. This time the flash is barely visible. That's about a '2'. Unplug the test CCFL, plug the original back in, move on to the lower left, and repeat. This one lights up like a CCFL in a monitor - we'll call it a '6', and the same happens with the one in the bottom center.

What does this tell us? Well, obviously the transformers are putting out plenty of power, but for some reason the one in the upper center isn't getting it's share. Now you know where to start checking.

Or as another example, let's say the two upper positions give a 'normal' brightness, the two lower positions don't give anything. Obviously, there is something wrong with transformer or driver for the lower CCFLs.

PlainBill

[Welchs101]

Re: IBM 6734-ABO Not working.

I made a little jig to try what you suggested.

I unplugged one of the lamp leads from the monitor and plugged in my jig in its place. I cycled power and .....nothing. The lamp did not flash.

I tested to make sure that the connections of my jig were good using an ohm meter. They were good....~ 0.3ohm.

I then shortned the wires of my jig thinking that perhaps the longer wire had to much resistance. Still nothing happened when i powered on the monitor.

I verified that the lamps inside the "bad" monitor flashed very very very quickly when i cycled power but nothing happened to my lamp jig when i cycled power.

The lamp could be bad but it is a "new" never used lamp.

Any thoughts?

[PlainBill]

Re: IBM 6734-ABO Not working.

I made a little jig to try what you suggested.

I unplugged one of the lamp leads from the monitor and plugged in my jig in its place. I cycled power and .....nothing. The lamp did not flash.

I tested to make sure that the connections of my jig were good using an ohm meter. They were good....~ 0.3ohm.

I then shortned the wires of my jig thinking that perhaps the longer wire had to much resistance. Still nothing happened when i powered on the monitor.

I verified that the lamps inside the "bad" monitor flashed very very very quickly when i cycled power but nothing happened to my lamp jig when i cycled power.

The lamp could be bad but it is a "new" never used lamp.

Any thoughts?

Did you test all four outputs of the IBM's inverter?

PlainBill

[Welchs101]

Re: IBM 6734-ABO Not working.

No. I only had time to test 3 of the 4. I will test all 4 again but i wont be able to do it until tomorrow.

Also, to make sure my setup is ok i plan on testing it on a "known" good monitor first then the "broken one". I will let you know what i find out.

Thanks again for your help.

[Welchs101]

Re: IBM 6734-ABO Not working.

Ok. I verified my little test setup using a known good monitor. I removed one of the lamp leads from a known good monitor and plugged in my test setup. The lamp came on. So i know my testsetup works.

Now when i go to the "broken" monitor i get "no light flashing" at all from any of the 4.

[PlainBill]

Re: IBM 6734-ABO Not working.

Ok. I verified my little test setup using a known good monitor. I removed one of the lamp leads from a known good monitor and plugged in my test setup. The lamp came on. So i know my testsetup works.

Now when i go to the "broken" monitor i get "no light flashing" at all from any of the 4.

OK, I guess that may make a little sense to me. If the CCFLs in the IBM have a lower start voltage than the test setup, that might happen.

Bear with me while I come up with another test.

PlainBill

[Welchs101]

Re: IBM 6734-ABO Not working.

No problem.

Do the ccfl's really have different startup voltages? I did not know that.

Learning something new all the time.

Thanks.

[alexanna]

Re: IBM 6734-ABO Not working.

One quick question,Did you or can you hook up the suspect monitor screen to your known good inverter? and if so what happens ? dose the problem follow to the good inverter?
Al.

[Welchs101]

Re: IBM 6734-ABO Not working.

I tested each of the "bulbs" of the bad monitor........is this what you mean? I connected each bulb of the bad monitor to a known good inverter/monitor and the good monitor worked for each of the bulbs on the bad monitor. Does this answer your question.

[alexanna]

Re: IBM 6734-ABO Not working.

were all four bulbs of the suspect panel hooked up at once the known good inverter? I have had bulbs that would light if they were checked one at a time but when all were hooked up to the inverter I would get the 2 sec problem.What I have found is a poor solder joint. It has to be because of the more load and heat.So if you can hook all up at once.
Al.

[Welchs101]

Re: IBM 6734-ABO Not working.

the bulbs were hooked up one at time.

i have seen the bad solder joint problem as well so what i do to try and test for this is once bulb comes on i "shake" the bulb/monitor undertest to see if it fluctuates. Probably not the best way but one that seems to work.