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

[killian6pk]

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

I just checked and it is on that site. Pick IBM from first drop down box and then L170 in the next and hit enter.

[budm]

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

Unfortunately, the diagram does not match his board, the circuits in the manual uses Royer Oscillator setup TYPE with different PWM IC.

[jetadm123]

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

budm- great job on tracing out the board!

[budm]

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

Thanks! you are correct that there are transistors for switching hte PWM IC ON/OFF.

[ilikesteel]

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

selldoor-budm-killian6pk-rtech,

wow, amazing what you guys can deduce without having the board in your possession!

the two 8 legged ic's are marked 4501M with 430162 underneath the 4501M. they do not look like have been electrically compromised.

do I need to connect the monitor back to a PC to verify the PO signal is being generated via the interface cable? I should do that before trying to jumper the small transistor or transistors budm pointed out in the diagram.

I did go to the website and looked at the manual for the L170. a more comprehensive manual than the one I found. the diagrams were definitely better. too bad it does not match my circuit board.

I'll look over the diagrams and study a little more. I'll double check back before I try jumping any components.

great work guys. will check it tomorrow. I'm in NJ and it's getting late here.

[budm]

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

We need to make sure that the reason the lamps turn off is not due to the Inverter on signal goes away, yes, you do have to connect the cable to running PC.
The service manual shows that it uses two transistor to turn on/off the inverter PWM IC, but the rest of the circuits are not the same as yours.

[ilikesteel]

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

budm&company,

I checked the voltage as indicated in red markings. yes, there was the 13V at the point you referenced. without the jumper in place there was 0 voltage at the indicated mark to turn on transistors. When I put the jumper in The 13V dropped to about 2.7 to 3.5 and kept fluctuating between those voltages.

The point where you said the transisitor should turn on was 2.76v and also varying between 2.76 and 3.5.

at no time was the monitor lit up with a screen image. I may try it tonight without any light in the basement coming through the windows.

thanks again... any more ideas?

[jetadm123]

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

Did you have the power board connected to the main board and video input from a computer to the main board when you made your measurements?

[ilikesteel]

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

yes, all were connected.....

[jetadm123]

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

If I understand things correctly, you jumpered the 13V directly to pins 13 and 18 of the BIT3105, which results in the voltage dropping between 2.7-3.5V

Unplug your monitor and try checking the transistor switch (that connects pins 13 and 18 to the 13V rail) that budm identified in his photo for a short. It's probably a standard NPN transistor.

[budm]

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

He need to put jumper in at the location I indicated, there is a current limit resistor that the 13v will have to go through first then it goes through the transistor (PNP) Emitter, the Collector is the output to VCC pin, I hope he did not connect the 13V B+ line directly through the VCC pin of the IC.
If the Main B+ in line drops down to 2~3VDC, it sounds like it cannot handle the load.

[jetadm123]

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

disregard.

[ilikesteel]

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

the jumper was connected from one end of the resistor (upper end) that has a black and white number on it, 8200, I believe. the other end of the jumper went above the transistor where there was a solder through component and a small round solder spot with no through the board component in it.

sound right?

getting anxious!

thanks guys.

[jetadm123]

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

Sounds like you correctly jumpered it after the current limiting resistor. With that jumper still in place try measuring the 13V output at the power supply connector that feeds the main board. If you still see the 2.7-3.5V, that would confirm budm's theory that the power supply cannot meet the load requirements.

[budm]

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

Or the PWM IC is turning on all the MOSFET's at the same time due to out put drive stuck high (The output drive is setup as a bridge output).
To very if the 13V supply is OK is to put a load on it and see if it can handle the current. I think there is an error printed on the board, it shows 13V @ 0.3A, that is way too low for driving 4 lamps circuit which will use about 20~30 Watts of power, 13V @ 0.3A is only 3.9Watts of power.
Try using 47 Ohms 5 watts resistor connected to the B+ LINE and ground (monitor plugged into the outlet but not ON) and see if it will maintain 13VDC.

[budm]

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

By the way, just want to be sure, the 13V that drops down to about 3V, is it measured at the IC or at the rectifier output?

[ilikesteel]

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

budm-adm123-selldoor and company,

attached are two pics of the jumper.

I started from scratch and rechecked voltages.

monitor connected to power. interface cable connected to pc that is powered off. power on the monitor is off. lamps connected to PS.

PS supply voltages at the connector with the one blue wire.

+14.25
+5.14

both are solid, no fluctuation.

at the jumper on the low side (as viewing the picture) of the 8200 ohm resistor, same voltage 14.25. on the upperside of the resistor I get 8.36v, same as where the jumper is attached above the resistor.

at the bit3105, there is 8.36v at pins 13 and 18, and it's solid.

With the monitor powered on and the PC powered on:

16.87V and 5.13V between gnd and the pins on the connector with one blue wire. from gnd to the low side of the resistor 8200, I have 16.87V. the opposite end of the resistor and the end of the jumper there is 8.36V.

from gnd to pins 13 and 18 on the bit3105 there is 8.36V. all voltages are solid no fluctuation.

I don't have a 47 ohm 5 watt resisior on hand to check the 13.V with an external load. If you think this is really the next step, I'll go and find one and make the test.

much thanks and patience....... what a crew.

[budm]

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

Post 47 "I checked the voltage as indicated in red markings. yes, there was the 13V at the point you referenced. without the jumper in place there was 0 voltage at the indicated mark to turn on transistors. When I put the jumper in The 13V dropped to about 2.7 to 3.5 and kept fluctuating between those voltages."
Now I am confused, where did you check and see that big voltage drop. in the your last post57, it does not look like you have that big voltage drop.

[ilikesteel]

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

budm,
reread post #47. I don't know how to answer that starnge occurance. in my last post I doubled checked all voltages as indicated. I did it twice and came up with the same solid reading voltages which were not fluctuating.

is the 8.36V a valid reading at pins 13 and 18?

don't forget the jumper is still in.

could the variying voltage levels I had before be because there was NO pc connection to the monitor? with the pc connected I don't see the flashing LOGO anymore, just a dark screen.

much thanks everyone..... hope we're close.

[budm]

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

When that jumper is installed, we are basically bypass the switch (transistor) forcing the inverter to be on (backligts on) all the time when you plug in the power to the monitor.
Since the 13V fed through a voltage dropping resistor, I do not expect the VCC for the I to be at 13V due to dropping resistor.
Do you see any lights on the backside of the panel at all? I think at this point you will need test lamp to verify the Inverter circuit function.