IBM L170 17" monitor "2 second on then black"

[ilikesteel]

I have this IBM L170 monitor which started to exhibit the 2 second on then black symptom. an electrician was replacing a light switch in my son's apartment and turned the breaker off. when he was done, he turned the breaker on, now the monitor will flash the IBM logo then go black. it keeps recycling with the same results.

I was able to verify in a darkened basement, that when the screen goes black, with a flashlight I can still see the IBM logo at a reduced brightness, then the screen will flash the logo at normal brightness and keep cycling. I can turn the monitor off by holding in the power switch.

all this is done without being connected to a PC.

The 5V and 13V are there. no bulged caps. it looks like the inverter is part of this power supply. the PS is made by samsung and the model is # IP 35135A. the pic below is a picture I copied from another post, disregard the black circles on the pic.

am I looking at a defective inverter in the PS?

Thanks to everyone on the forum for any help you can provide.

[jetadm123]

Re: IBM L170 17" monitor "2 second on then black"

Good work on troubleshooting so far. Unfortunately, I can't open your photo. I would check to see if there's a fuse between the 13V output and inverter section.

[selldoor]

Re: IBM L170 17" monitor "2 second on then black"

Picture is only 4kb it is too small in any case it is no use us looking at pictures of other boards it is yours we need to see.
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

[ilikesteel]

Re: IBM L170 17" monitor "2 second on then black"

ok, took some pics, hope they're viewable. I also download the so called service manual for the schematics. the schematic of the power board doesn't show input power and the bridge and filter circuits. If they're on that schematic, I couldn't find it.

hope pics help. thanks.

[jetadm123]

Re: IBM L170 17" monitor "2 second on then black"

In your 3rd photo there are two 8-pin surface mount devices marked 4501M. I believe these are AP4501M dual mosfet devices containing both N and P-channel mosfets. With your meter set to resistance, check for shorts across:

G1-S1
G1-D1
D1-S1

G2-S2
G2-D2
D2-S2


Perform the above test for both AP4501M.

[ilikesteel]

Re: IBM L170 17" monitor "2 second on then black"

jetadm123,

checked both 8-pin mosfets 4501M's. I used a Fluke D-802 digital meter. I tried the 200 ohm scale (my lowest) and also the 2K ohm scale.

each mosfet gave the same reading as follows:

G1-S1= open
G1-D1=open
D1-S1=open

G2-S2=open
S2-D2=open
D2-S2=open.

thanks... what's next?

[jetadm123]

Re: IBM L170 17" monitor "2 second on then black"

The ccfl controller chip, BIT3105, is located between the two inverter transformers. Check to see if it's Vcc pin is getting any voltage.

[budm]

Re: IBM L170 17" monitor "2 second on then black"

Check the inverter transformer secondary winding resistance? It can also be bad lamp assembly, to verify that you will need test lamps. Check the transformer first.
https://www.badcaps.net/forum/showthread.php?t=19987

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

[ilikesteel]

Re: IBM L170 17" monitor "2 second on then black"

jetadm123,

data sheet for BIT3105 showed a PVDD and a AVDD for input voltage between 4.5V and 13V.

pin-3=AGND
pin-8 PGND

pin-13=PVDD
pin-18=AVDD

using pin 3 and 8 as GND, There was 0 voltage on pins 13 and 18. "0" voltage.

thanks..... saga continues ...

[ilikesteel]

Re: IBM L170 17" monitor "2 second on then black"

budm,

can the transformer resistance be checked while they are onboard and in circuit? would a data sheet provide resistance readings?

thanks...

[jetadm123]

Re: IBM L170 17" monitor "2 second on then black"

I believe those two pins are fed off the 13V rail and now we need to find out why the 13V is not reaching the inverter section. The power supply is made by Samsung and used in several models. Some versions of this power supply did use a fuse between the 13V output and the inverter section. And in most cases they hid the fuse using white silicon adhesive. In your second photo, lower right side, above the wiring harness with the blue wire, there are two caps and a inductor with white adhesive between them. Carefully, remove some of that adhesive to see if there's a fuse there. It should be green in color.

[budm]

Re: IBM L170 17" monitor "2 second on then black"

If the 13v does not reach the PWM IC, it just does not make sense that the lamps will even flash on since there will be no drive voltages to the Gates for the MOSFET's that drive the inverter transformer, strange indeed.

[ilikesteel]

Re: IBM L170 17" monitor "2 second on then black"

budm-adm123,

Ok guys. I'll check for the fuse tomorrow. hope it's the fuse. thanks again for you efforts!

[jetadm123]

Re: IBM L170 17" monitor "2 second on then black"

Oops! I guess I should have read the original post a little more carefully. I agree with budm that without 13V, there would be no flash from the ccfl's. However, you say that the monitor continually cycles with a flash, black screen, flash, black screen, etc. Possibly a problem with the logic card continually sending on/off signal?

[budm]

Re: IBM L170 17" monitor "2 second on then black"

He may have to verify that voltage reading on that PWM IC power pins again.

[selldoor]

Re: IBM L170 17" monitor "2 second on then black"

budm,

can the transformer resistance be checked while they are onboard and in circuit? would a data sheet provide resistance readings?

thanks...

Yes you can test on board - I have been looking for a TM-130 but have struggled so far, so if one is faulty it could be a problem to replace.

I have been trying to find a pinout for the secondaries may just be the
outer two joints at the end where there are three (under the plastic)
or it may be as in the attached pic.
If not you will just have to work around all the pins in sequence.

Meter on 2000 ohms.

[ilikesteel]

Re: IBM L170 17" monitor "2 second on then black"

selldoor-adm1213-budm,

ok, I checked a few things and here's what I found. attached are more photos, one is a view of the transformer pin view and the other of the power supply board indicating NO fuse where the two caps and inductor are located. on the pin view of the ransformer looks like there is a wire attached to first inside pin from each end of the 6 pins. opposite end of transformer shows 3 pins. both transformers are identical.

I rechecked my voltages again. with the monitor connected to the ac power, at the 9 pin connector ( all black wires except for one blue) that has the cable going to the scaler board, I read 5.14V for the 5V and for the 13V it reads 15.47V.

turning power on, the monitor still flashes the IBM LOGO at normal brightness for 1 second and then goes blank for about 2-3 seconds. this keeps cycling until I turn power off.

While the cycling was going on I checked the 5V and 13V at the same connector and found this: the 5V reading was 5.14V and would drop to 1.3V as the cycling continued. 5.14V~1.30V.

the 13V reading was 16.8V and would drop to 10.8V as the cycling continued. 16.8~10.8

also noticed that all the electrolytic caps were CapXon and looked original to the board.


BIT3105 still did not have any voltage on pin 13 or pin 18.

the data sheet indicated the following:

pin3= AGND = GND pin of analog control circuitry
pin 8=PGND GND pin of output drivers.
pin 13=PVDD= ps 4.0v~13.2 v for output drivers.
pin18=AVDD= ps of analog voltage control circuitry.

somewhere I read in the DS that PVDD and AVDD = VDD input voltage should be the same. If I'm checking bit3105 incorrectly let me know.

Is the consensus the PS may be bad? I've seen them available new and used from china. I wish there was a viable schematic of the power supply that would indicate all the information and a parts list for the board.

thanks again..... still hoping.

[selldoor]

Re: IBM L170 17" monitor "2 second on then black"

Ok just test the transformers on the two bigger pins shown in your picture.
Power off ( 5 minutes). If they are the wrong pins it wont do any damage.

[selldoor]

Re: IBM L170 17" monitor "2 second on then black"

The cycling may relate in some way to it not being connected to a pc (instead of it displaying no signal it goes into a selftest loop?) Was it connected when the fault first started?

[Rtech]

Re: IBM L170 17" monitor "2 second on then black"

Its not easy when you have no schematic,and trying to help,but i think you should try and split the circuit eg one or more of the links on the board will take the 13v up to the inverter side of the board, and I would trace which ones they are, and open them,now the Power Supply up to them is on its own, and you can now measure your 5v and see if that now jumps up and down.if its fine then the Inverter part is at fault,or if its still varying erratically then the front end of the cct is where the problem lies.