Need help with Samsung T220

[caboose1835]

Alright. Back after some more tests.

Backlight works. Theres no doubt about that.

The backlight worked with a 1k resistor between Pin 5 and Pin 8 but It was giving off a weird sound but the whole panel does light up.

Before I did that, I checked for continuity between Pin 8 on the power board side and the other end (so I can insert the resistor on the other end instead of jamming it on the power board connector, you know safety and all. I was checking for continuity because I thought the wires changed places from connector to connector.) and i noticed that when I shorted Pin 8 (On/Off) to Pin 2 (13.0V) through the continuity setting on my multimeter the backlight turned on nicely. I also got a reading of 12.9V between Pin 8 and Pin 2. Im assuming that is to be expected?

I did not test a 1k resistor between Pin 7 and Pin 1 as I have determined that the B/L works, however would it help to see what happens?

[R_J]

Now we know the backlights work. but its not seeing the BL on command FROM the logic board, although it did change slightly.
The extra resistor was to turn on the dimming if needed, it was to go between +5v and either pin 1 (BL_ADJ_PWM) OR pin7 (BL_ADJ_ANALOG). NOT between 1 & 7.

Now you can start using the service mannual as it has the logic board schematic.
First check the regulator voltages, IC603 (+3.3v), IC601 (+3.3v) and IC602 (+1.8V)

Check the transistor Q601. This transistor is what enables the backlight.
You can check the voltage on the base and see if it changes when the monitor is turned on and off. It should be around 1~3 volts and 0
Also check the voltage on CN400 pins 1,2 or3 (LVDS cable to panel) It should have +5_PANEL +5 volts. If you do not have +5_PANEL, check the voltage on Q202, Q205 and finally Q206.

Post a picture of the logic board.

[caboose1835]

I actually just checked IC601 IAW section 4-2 of the service manual, with the monitor in the ON state.

IC 601
Pin 1 GND
Pin 2 3.296V
Pin 3 5.21V
Tab 3.29V

Capacitors
C628 5.21V
C630 3.296V
C629 3.296V

LB photos will follow

[caboose1835]

logic board photos

[caboose1835]

Q601
Base/Emitter : ON 0.618V Off 0.068V
Base/Collector : ON 0.156V Off 0.038V

CN400
Pin 1-3: 5.21V

[R_J]

Are you mesuring the voltage on Q601 across the transistor? Just measure the voltage to ground. Q601 could be bad. It's collector should switch between 0 and 5 volts.
Look at the schematic for Q601, If the transistor base is 0 volts the transistor is in open state and the voltage on the collector will be close to +5 volts (turning on the BL_EN) If the base is above .6 volts the transistor is turned ON and the voltage at the collector will be close to 0v (turning OFF BL_EN)

CN400 pin1~3 5v is good, the panel/tcon is getting voltage, does this voltage also change when the monitor is turned off with the power switch?

[caboose1835]

My apologies for CN400. I do not have +5V to GND on Pins 1,2,3. I tested that as Pins 1,2,3 to 5.1V not to GND.

Q601
On---Off
1.0.00---0.00
2.0.028-0.033---0.625
3.0.027---0.800

Pin 2 on Q601 seemed to be a little affected by the multimeter or it was just reading all over the place. Sometimes I would read 0.070 or 0.018 or 0.050. It was never consistent except around 0.020 and 0.035

Ill report back with Q202, Q205 and Q206.

[caboose1835]

Q202,204,205,206. First reading in ON state, second reading in OFF state.

Q202

1. E 0---0
2. B 0.467---0.653
3. C 0.049---0.023

Q204

1. E 0---0
2. B 0---0.625
3. C 0.016---0.170

Q205

1. E 0---0
2. B 0.049---0.023
3. C 0.056---5.15

Q206

1. 0---0
2. 0---0
3. 0.056---5.16
4. 0.057---5.21
5. 0---0
6. 0---0

[R_J]

Transistors are labled emitter, base, collector, not 1,2,3. I have no idea which is the emitter, base etc.
I think Q601 is shorted emitter to collector, or R600 is open

How do you know when the monitor is ON or is OFF? Your readings suggest otherwise for example Q206, pin 4 you have 0 volts ON state and 5 volts OFF state.

Did you ever check the front led? Fix it so you know when the monitor is on or off, The LED comes on when the monitor is ON, NOT when it is in standby.

[caboose1835]

Sorry about that, slipped my mind.

Corrected now except for Q206. I tried looking for a datasheet, and couldn't find one. Is that 2 transistors in a DIP6 package?

R600
6.48k ohm

Q601
E/C 6.50k ohm

As for how I know the monitor is on or off, I listen to the transformer while hitting the power button. When it goes the sound changes. I also totally forgot about standby states when a monitor is on but would normally "timeout".........Damnit. Gotta fix this LED.

Is there anywhere I can add a bog standard LED while doing this testing? Or do I had to swap out the thing

[R_J]

What are you using as an indication the monitor is ON or in STANDBY?

[caboose1835]

unfortunately, Nothing. I listen to the transformer for a change after touching the switch. However I just tested the LED with a 9v battery and a 1k resistor and it works.

When I mean the ON state for the panel I meant it as ON state for the boards.

I have a feeling I shouldnt have made that assumption

[R_J]

Originally Posted by caboose1835

I just got all voltages for every pin on CN2,3 in on and off states

CN3

1. GND-----GND
2. 0.000-----1.813
3. 0.157-----3.070
4. (-)0.001-----2.198
5. 3.311-----3.313

Pin 4 is the supply for the led, When there is voltage on it the led should be on
That 5 volts on Q206(4) which is a p channel mosfet, is the switched +5V_MAIN, it there only when the monitor is ON. and not when it is OFF.
When you have +5V_MAIN, You should have 5 volts on one side of R600 and about 4 volts on the other side, this would be the Backlight enable line. if you don't have it, try shorting Q601 base to ground and see if the backlights come on.

[caboose1835]

Originally Posted by R_J

You should have 5 volts on one side of R600 and about 4 volts on the other side, this would be the Backlight enable line. if you don't have it, try shorting Q601 base to ground and see if the backlights come on.

I had 5.21V on one side of R600, and 0.805V on the over. Shorting the Base to ground worked, but when I did it through my multimeter continuity setting it flickered quietly, and when I used a straight wire as well as a 1K resistor, the transformer squealed like a pig.

Also when I measure the resistance of the base on Q601, I get an open loop regardless of monitor state.

Is it safe to assume Q601 is a culprit? Or is it R600?

[caboose1835]

bump

[R_J]

Originally Posted by caboose1835

I had 5.21V on one side of R600, and 0.805V on the over. Shorting the Base to ground worked, but when I did it through my multimeter continuity setting it flickered quietly, and when I used a straight wire as well as a 1K resistor, the transformer squealed like a pig.

Also when I measure the resistance of the base on Q601, I get an open loop regardless of monitor state.

Is it safe to assume Q601 is a culprit? Or is it R600?

You say shorting the base to ground worked. so you got backlights when you did that?

Why are you checking continuty on a live board? What are you checking with your meter when all I asked was to short the base and emitter of Q601 to see if the backlight would come on.
Then you say you used a straight wire as well as a 1k resistor. For what? where? What transformer squealed? the switching power transformer? the backlight transformer?

[caboose1835]

Shorting the Base and Emittor on Q601 turned on the backlights

[R_J]

Ok thats good, that means Q601, the power supply/inverter, ccfl's are ok and q601 is not getting a command from the microprocessor.
On CN600 pin 11 or pin 12 (key1 or key2)one of the lines should change when you press the power button, which one changes and what is the change (ie: 3.3~0)

[caboose1835]

CN600

Key 1 (Pin 11) ON 3.066V OFF 0.157
Key 2 (Pin 12) ON 1.812V OFF 0V

[R_J]

Originally Posted by caboose1835

CN600

Key 1 (Pin 11) ON 3.066V OFF 0.157
Key 2 (Pin 12) ON 1.812V OFF 0V

Ok lets assume when the monitor is on according to these voltages, IC604 should be switching the +5V_IP from the power supply and supplying the +5V_MAIN to the rest of the main board.
So Key1_out turns on Q206, which turns on IC604 supplying +5V_MAIN and acording to your other measurements you are getting +5V_PANEL voltage, and +1.8V volts

Q601
On---Off
1.0.00---0.00
2.0.028-0.033---0.625
3.0.027---0.800

I am guessing one of those pins is the base and if shorting the base to emitter results in the backlights being ON, then 0.0x volts should also result in the backlights being ON