Dead T41 - (type 2374-7FG)

[edkedk]

Hi all,

I am new to this forum and this will be my first post.
I own a second T41 (2374-7FG), but this one does not power on. No led will turn on, Not with adapter only (adapter is OK), Not with only a full battery connected, and not with both connected.
The keyboard on-button is working (this keyboard was tested in a working t41).
The memory is 100%, as is the hard drive and wireless mpci card.
For the sake of intervention i removed the harddrive, the mpci wireless card and i remove the battery.
So with this situation i try to power up with only the adapter connected. Nothings happens.
Not even a beep or a blink from a led. Fan is not moving at all, not even a small glitch in movement.
The screen remains dead too.
I tried remove the cmos battery totally and boot wihout it, no solution.
I tried the famous power on/ button pressing it many times with one second in between, and after that 30 sec keep the power on button pressed. no solution.

Today i disassembled the whole t41 to check all the fuses. All fuses seem ok.

What can I check more ? I have solder experience.
Furthermore I would like to know if I connect the adapter to the mainboard only, so no lcd display connected, no harddisk, no mem, no keyboard etc.. what is happening to the DC voltage at ex. pin of the atmel chip (has 8 pins) ?? That is my reference point. There I sould measure 5V at pin 8 when the mainbord is powered on. When I measure the voltage between pin 4 (Vss/ ground) and pin 8 (Vcc / 5V) I measure 0 Volts.
What I do not know is that I _should_ measure 5 Volts on the Vcc pin there when I only connect the adapter to the bare mainboard (with cpu). Or will there be 5V only when the T41 is power on via the keyboard ?
I also looked at all components, can not find any brown coloured solder points, no blown up capacitors, FET's etc.. All components look good.

[hhmcsv]

Sorry that nobody has answered your post, and I cannot help much, but I am using the exact same Thinkpad as yours, and that is working perfectly. Could sound like a faulty motherboard, but that is only a wild guess.

[RealBlackStuff]

Welcome to the Forum.
If you remove both RAM modules, then try to start, do you hear any beeps? For no RAM, it should be 1-3-3-1.
If you don't hear anything, your prospects are bleak.
With some RAM in, try to power on while lifting the keyboard and pressing on the ATI chip under the KB.
Go stand in line with all the others having GPU problems.

[edkedk]

Without any RAM module I hear no beeps at all.

Should the T41 startup without RAM memory ?

[RealBlackStuff]

It shouldn't, but the beeps are a signal that there is still some life in the old dog, eehhh... motherboard.
No beeps mean dead mobo normally.
What about pressing on the GPU?

[edkedk]

I tried pressing on the GPU from ATI while pressing the power-on button on the connected keyboard but that was without RAM module.
Acutally I have only the bare mainboard now on my table with only the cpu in, and the adapter attached.

I will try with one RAM module now, and I will try it in both SO-DIMM slots.

[RealBlackStuff]

If you have a bare mobo, you won't hear any beeps, until you connect the speakers again!
You need RAM in while pressing on the GPU.
No RAM while checking for any life signs.

[edkedk]

I connected the speakers, no beeps while pressing power-on button and at the same time pressure on the ATI gpu area.
Fan is dead also.

I suspect a MOSFET near the adapter connector on the mainboard is defect.
This morning I measured voltage on all three MOSfet's, they are located very close to the adapter power plug.
Two of them give about 16.7 Volts on the output pins, the third and last MOSfet in the chain seems to have very low output voltage, about 0.7 Volt.
Maybe I made a mistake with measurement because I did not write it down. Maybe I should try to compare with my working T41 which could be a good reference. I can then compare the working mainboard with the defective and check voltage levels on some locations.

I will give an update a.s.a.p.

Thanks so far for your fast replies !

[SMA]

Start by inspecting the MAX1631, it is the heart of the power circuitry.
Download its datasheet and measure the input and output voltages of that chip.
The MAX1631 should turn on immediately after the power supply has been connected, independent of the state of the power switch.

There is no need for you to keep the cpu on the board. Consider taking it out and putting it away while measuring.
The bare board and the power supply should be enough for this fault finding.

[edkedk]

Hello SMA,

I have located the MAX1631. Hopefully I can measure the voltage on all pins.
All the pins are so close to eachother I have to be carefull while measuring. Hope I can do it with mu multimeter.
Otherwise I will probably need a special tool with very thin tips otherwise I could make a shortcut between to pins.
Maybe I need a magnofy glass to carfeully put the measure probe from the multimeter on each pin of MAX1631.

Shall I post the measure results in this thread ?

[SMA]

I did not mean for you to do all the pins in turn and the need to measure directly on the chip should be rather limited,
unless the problem is actually with this chip. The input and outputs will do.

The input voltage is on pin 22 and it usually goes through a 10 ohm resistor. The voltage should be the power supply voltage (16V).
If the input voltage is not there, then there will be no need to make any further measurements on this chip.

The output voltages should be 3.3V and 5.0V DC. If both output voltages are there then you will be done with this chip.
The easiest place to get to the 2 output voltages are on the power inductors or the output capacitors.

I believe that you will know how to post the results once you have it.

The datasheet can be found here

max1631 datasheet

[edkedk]

Measurement result of the relevant MAX1631 pins (I did measure them all )
1,2,3,5 = 0 V
4 = 4.99 V
6 = 4.99 V
7-14 = 0 V

15,16,17 = 0 V
18 = 4.68 V (Boost capacitor connection for high-side gate drive (0.1μF)
19 = 4.99 V (Gate-Drive Output for the low-side synchronous-rectifier MOSFET. Swings 0V to VL.)
20 = 0 V (power ground)
21 = 4.99 V (output voltage)
22 = 15.85 V (input voltage)
23 = 3.29 V (Shutdown Control Input, active low.)
24 = 4.99 V (Gate-Drive Output for the low-side synchronous-rectifier MOSFET. Swings 0V to VL.)
25,26 = 0 V
27 = 0 V (Pin Gate-Drive Output for the 3.3V, high-side N-channel switch. DH3 is a floating driver output that swings
from LX3 to BST3, riding on the LX3 switching node voltage.)
28 = 0.96 V


NOTE: Only pin nr 23 showed 3.29 Volt. The datasheet says this is input (Shutdown Control Input, active low.)

Compared with your information, I can conclude that all the DC voltages with the MAX1631 are ok, EXCEPT pin 27 ?
The MAX1631 receives a "Power Good" signal which says it should start working (pin 23 ?).

I think that PIN 27 should give 3.3 Volt as output, am I right ? And I measure 0 Volt there. So that output is the only one which has not the expected voltage value.

I did some further checks....about the 3.3 V missing on pin 27...This pin is connected to pin 2 of TPC8A01, a MOSFET dc-dc converter which is close to the MAX1631 on the mainboard.

Pin 2 of this TPC8A01 is a GATE input.

From datasheet of TPC8A01:

1 SOURCE 4 GATE
2 GATE 5, 6DRAIN/CATHOUDE
3 SURCE/ANODE 7, 8 DRAIN


On pin 2 of TPC8A01 (GATE), I measure 0 V (which connects to the MAX1631, pin 27)
pin 4 (GATE) measures 5 V
pin 7,8 (DRAIN) measures 15.85 V.

Looks like one GATE is not enabled / gated ?

Does this all mean that the MAX1631 pin 27 does not output 3.3 Volt output for the GATE of TPC8A01 ?
Is the MAX1631 broken because of this fact ? Or does the MAX1631 miss some input voltage somewhere which is the reason for not outputting 3.3 V at pin 27 ?

If the gate on pin 2 of TPC8A01 remains 0 V then I can imagine that at least one MOSFET will never be "gated" and so this MOSFET will not deliver output then ? I do not know much about analog electronics how all stuff works.

What could be the next step in further investigation ?
I want to thank you for your quick reply so far , you have given me hope in fixing my broken T41 and bring it back to life !

[SMA]

The input voltage on pin 22 is fine, so the mosfet's you were suspecting this morning must be working fine. The supply voltage is getting
through.

When measuring, it may happen that one gets the wrong result because the measure probe is not making contact with the point being measured.
The meter will usually show a 0V reading in such cases.
I beleive that this may have happened to you on pin 9, the REF pin. It should read 2.5V.
Possibly you have also missed pin 25 (and 15).

You'd better recheck the 3 mentioned pins ( 9, 15 and 25 ) so that we are not making any false conclusions.

The max1631 chip is missing some control inputs on pin 7 and 28, so the 3.3V and the 5V does not turn on.

It is getting a little late, so I will have to leave for today. Will be back tomorrow.

[edkedk]

Ok, I will try to measure pin 9, 15 and 25 again, and double check.

In the datasheet of MAX1631 I read this:
"RESET is held low until both the 3.3V and 5V SMPS outputs are in regulation."

In fact, i measured 0 V at the ~RESET pin, so thath means it it still in reset state, even way after 32,000 system cycles.
And the 3.3 Volt output is not there, only 0 V in stead of 3.3 V. So, because 3.3 V output is not in regulation, the MAX1631 keeps the reset active ?

Results of the measurement of above three pins will follow.

[edkedk]

Hello SMA,

I measured from MAX1631 the pins 9,15 and 25:

pin 9 = 0.77 V - 1.22 V (the REF pin. It should read 2.5V.) -> most times I measure around 1.06V, changes a bit between 0.77 V and 1.22 V. So this is too low voltage and not stable.

pin 15 = 0 V
pin 25 = 0V

Both pin 15 and 25 I did measure many times, I also checked I have the right pin to measure, they are both 0 V.

[SMA]

An unstable and low REF voltage on pin 9 is not the way it is supposed to be.
According to my notes, pin 9 and pin 15 should be connected together, but that must be different on your board - not a problem.
0V on pin 25 is not correct either.

This is a dilemma, as this indicates a problem with or around the max1631 and
the missing input on pin 7 and pin 28 indicates a problem elsewhere.

Do you have a port replicator ?

[SMA]

Well, having thought a little more about it, the dilemma I was referring to isn't really a dilemma, cause the indicators
saying that there is a problem around the max1631 are so strong that some repair is needed in that area.

I am unable to tell exactly which component(s) to replace and there are no certain way of measuring that, but something can be done.

There should be a small 10 ohm resistor connected to pin 22. Its actual value can be measured.
The boost diodes can be measured.
The mosfets can be checked for shorts.

If it was me, I think that I would try to replace the max1631 chip if none of the above reveals something.

[edkedk]

SMA Thank you for your tips / replies.

I do not have a port replicator.
I was wondering what could be the cause that the mainbord has a problem.
Mostly bacause of some shortcut ? on external ports, like usb, ps/2 or memory dimm module.
All the fuses are 100%.

How do the boost diodes look ? Do you have a small picture/photo ? Or type number of this component ?
How can I find and identify them on the mainbord ?

I will check some small smd parts you mentioned.

When there is no solution for repair I will use it for spare parts for my other T41.
I was thinking as a last hope to use my other T41 as reference. So compare measurments on some components and then compare the voltages measured on both mainboards. Because 1 of them is in working condition, I should have good reference for comparison.