T42 DC Connector Problem- is this unique from other people's

[nykobing06]

Hey all, happy new year!

I've got a problem that culminated into an apparent failure today...this only three weeks after I replaced my fan!

Today, the battery stopped charging even with the adapter plugged in. After hours of reading, I narrowed it down to two possibilities.

1. the screw holding the connector is loose (though this alone doesnt explain why even wiggling the cord did no good).
2. the leads broke off.

I opened the computer and detached the LCD. To my surprise, the leads between the connector and the socket on the system board were intact. The screw was loose and I tightened it but this did not solve my problem.

I'm not very savy with electrical systems and don't have an ohm meter...so I couldnt check for connectivity (continuity?). The only visible inconsistency is a slight burn mark on the lead that looks like < within the yellow connector. Its right on the bend.

Simple question is...can the burn mark indicate a faulty connector? Even so, it doesn't explain the fact that before this failure, my T42 would shut down completely and abruptly when the power cord was pulled or moved nor does it seem to explain that wiggling the power cord reconnected power to the laptop after lapses in power due to chord movement. I suppose the only way to be sure is to use an Ohm meter and check the connections? I'm fairly positive it isn't the AC Adapter but worth a shot.

Thanks for the help!

EDIT: I did read the multiple threads on this issue but all of them seemed to have visible, definitive problems with the DC connector (and no discussion on burn marks). From observation, mine seems perfectly good minus the the burn mark.

[Harryc]

Are you saying that the machine works on AC power without a battery? What happens when you boot with a battery inserted? Orange battery light flashing? How old is this battery, and can you try it in another machine? There is a fuse involved in battery charging, but you'll need a multimeter to check it.
Here's the thread describing the fuse location. You have to remove the systemboard to get at it ... have fun.

[poshgeordie]

From what you say two things come to mind:

1. One/ both leads in the AC adapter plug into the TP are snapped. Difficult now to check this, but normally if the TP sometimes works if you hold the plug in a position which provided DC power then if you waggle the cable into the plug and the DC power comes and goes then it's (a) snapped wire(s) into the DC plug.
If not then it's elsewhere.

2. Burnt internal cables from the back panel DC socket to the motherboard 4 way socket. Indicates a previously trapped cable which can happen when you plug in the LCD connector; it's easy to get one of the DC cables caught under the connector and slice the insulation which will cause a short to negative/ground and insulation burn marks.
This could blow your AC adapter even though they should be short circuit protected, or as Harry says a blown fuse.

If you've not got access to another AC adapter and no test meter, you'll need to know if it works or not.
Give me a few minutes & I'll get back with a simple AC adapter tester using a couple of components.

I've replied to your PM too

<EDIT> family calls & I'll get back later with a drawing. For the teckies I was thinking of a simple LED and resistor in series with leads twisted together.
If someone has time can they source a suitable led and calc the resistor and do a quick sketch with part nos and where to get in USA etc.
I can do one tonight if no one does.

[sjthinkpader]

I just replaced a DC jack in a R52 that felt loose. The side contact in the jack was pushed in for some reason. So the computer would switch between line power and battery power intermittently.

I had this jack from a parts machine. Unfortunately it took a complete disassembly including detaching the LCD to replace the DC jack. A T4x is slightly different from a R5x in the rear area but level of work to replace this jack is similar. Note that there is no need to remove the fan/heatsink assembly. It is not attached to the case.

[poshgeordie]

I've got a circuit and building instructions to test that the AC Adapter is producing 16V DC from the plug.

Anyone can make it by simply twisting two easily obtainable component leads together:

DC Tester

It means now that if you have intermittent power from the adapter into the TP, you can use this to see if the connector, lead or the AC adapter itself is broken before tearing the thing apart.

[nykobing06]

First off, thanks for the prompt reply people, I really appreciate the help.


The laptop can only run on battery power. Plugging in the AC adapter does nada. At this point, the battery is completely drained with the orange flashing light lighting up for a quick second or two upon starting the computer and then the computer abruptly turns off (due to lack of power).

From my visual inspection, there are two wires (probably soldered to the yellow connector), that lead from the connector to a pin-socket connector located on the MB. Those seem to be intact. When I first took the LCD off, the screw attaching the connector was very loose. I tightened that. The connector strip within the yellow connector is bent as such < and so I'm assuming contact with the power adapter plug is being made. However, this strip has a noticeable mark on the protruding edge < but I'm assuming its because of the numerous plugging in and pulling out of the power cord.

[poshgeordie]

I think I'm right in saying that there should be 4 wires (not 2) from the yellow connector, two positive and two negative and all the same creamy colour.
They then go into a little 4 way connector into the m'board.

That connector should be upright and at 90 degs from the m'board.

I would suggest buying a new DC yellow connector and wire assembly from that link I gave above and see if it sorts you out.

[nykobing06]

From what you say two things come to mind:

1. One/ both leads in the AC adapter plug into the TP are snapped. Difficult now to check this, but normally if the TP sometimes works if you hold the plug in a position which provided DC power then if you waggle the cable into the plug and the DC power comes and goes then it's (a) snapped wire(s) into the DC plug.
If not then it's elsewhere.

2. Burnt internal cables from the back panel DC socket to the motherboard 4 way socket. Indicates a previously trapped cable which can happen when you plug in the LCD connector; it's easy to get one of the DC cables caught under the connector and slice the insulation which will cause a short to negative/ground and insulation burn marks.
This could blow your AC adapter even though they should be short circuit protected, or as Harry says a blown fuse.

If you've not got access to another AC adapter and no test meter, you'll need to know if it works or not.
Give me a few minutes & I'll get back with a simple AC adapter tester using a couple of components.

I've replied to your PM too

<EDIT> family calls & I'll get back later with a drawing. For the teckies I was thinking of a simple LED and resistor in series with leads twisted together.
If someone has time can they source a suitable led and calc the resistor and do a quick sketch with part nos and where to get in USA etc.
I can do one tonight if no one does.

Thanks for the replies Nick..and the PM. By the way, I'm also sick . lol

As for the DC tester, thanks a bunch! I'm going to get the parts today. Does Radio Shack have leds and resistors or do i have to go to a specialty store? I know I can order them online but if I can get them from a store, I could test it out today or at the latest, this weekend.

I was a bit confused by your reply though. The possible burnt cables you're talking about connect the yellow dc connector to the MB, right? In that case, I would have to replace the Yellow dc connector right?

When you refer to the snapped wires, are you talking about the ones connected to the Yellow connector (soldered) and connect to the MB?

To me, you are referring to the same wires in both case so I'm thinking im confused lol.

All I do know is that upon visual inspection, the wires connecting the yellow dc connector to the socket on the mB (4 way or 4 pin, however you call it) are intact...both ends are connected. The only abnormality is a little mark on the side connector strip WITHIN the yellow connector but that could be ware and tear from sliding in the power plug in and out.

Regarding the DC Test, I can use that to check if the Adapter is working. How would I check to see if the DC connector is working without an Ohm Meter? And by that I mean how can i check to see if when power is supplied to the yellow dc connector, it is then correctly supplied to the MB?

My guess is at this point, its between the yellow connector and fuse...one of those failed/blew.

[nykobing06]

I think I'm right in saying that there should be 4 wires (not 2) from the yellow connector, two positive and two negative and all the same creamy colour.
They then go into a little 4 way connector into the m'board.

That connector should be upright and at 90 degs from the m'board.

I would suggest buying a new DC yellow connector and wire assembly from that link I gave above and see if it sorts you out.

Hey Nick,

I think you're right (I have since reconstructed my thinkpad fearing I may lose parts/screws). There are two wires BUNDLES i think I should say. Its two black chords that (when looking at the open thinkpad - facing you as your would normally use the computer), one is attached to the back of the yellow connector and the other to the side. The one on the side is harder to check if the connection is correct, however, I couldn't see any fault in them.

I think you're right though, I may as well just buy the yellow connector and attach it.

You guys weren't kidding when you said you had to take the whole thing apart to get to this connector lol.

I seem to see a lot of these problems cropping up...lenovo should make an easy route to these connectors...back door or something!

[poshgeordie]

OK, from Radio Spares you need something like this one.
It's slightly different but OK with the same resistor.
LED spec: around 1.9V and 20mA. It can be any physical size.
Resistor: 720 to 1000 ohm, 0.25 watt, carbon or metal oxide (note the bigger value resistor will make the LED slightly dimmer).

You can use this as well to check for 16V on the m'board by VERY CAREFULLY putting the short lead end of the LED on the chassis and the resistor wire to probe the fuse next to the mbrd power connector.

Reading the rest of your queries, I think we've ended up talking at cross purposes.
I would suggest getting to Radio Shack for the LED and resistor and check the AC Adapter connector and then the 2 x +ve and 2 x -Ve black wires onto the 4 way mbrd connector from the yellow connector.
And so on.

Hope I've not complicated this any more!!

[nykobing06]

Thanks posh, I appreciate the help.

I'm ordering the part today...took a week to attend to other things. Now that my T400 is going back to Lenovo (getting a replacement), I'm going to need to get that T42 up and running.

I'll keep this thread updated.