A31 AC Power Problem

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gb_ibmguy · #1 Post by **gb_ibmguy** » Sun May 10, 2009 3:21 pm

My a 31 just started to have a problem with the power adapter. It is always plugged in to the wall. and on AC power. Now the AC adapter connector is getting strange. Have to wiggle it and plug in and out before the TP sees that it is on AC power. I fear that the AC connector on the TP is loose, going bad. Any ideas???

#2 Post by **Harryc** » Sun May 10, 2009 4:14 pm

You need to replace (or resolder) the power jack on the A31 systemboard, and you need to remove the systemboard entirely from the machine to do it.
http://cgi.ebay.com/DC-Power-Jack-for-I ... 0340489970
http://www-307.ibm.com/pc/support/site. ... 39796.html

gb_ibmguy · #3 Post by **gb_ibmguy** » Mon May 11, 2009 5:47 am

Thanks for the quick reply! I ordered the part last night and now just have to wait.

However, seems a new or related issue has appeared.
The main battery ran down last night, since the AC wasn't making a connection and I left it turned on. This morning I remembered that I had a port replicator for these units. Great, I thought, I can bypass my flakey connector and use the port replicator and be good to go. No Dice. No power, no lights, no boot. Figuring the battery may be shot, too low to charge, I swapped it with the good-full charge battery from my other A31. Connected it to the port replicator again, and still no lights. The laptop turns on for a brief moment and then shuts down. I tested the port replicator with the other A31 and all is well.
So, I wonder, is this all due to a loose power connector or did I blow some fuse or should I start looking for a new mother board?

#4 Post by **Harryc** » Mon May 11, 2009 7:32 am

- unplug system and remove battery

- press the power button ten times repeatedly

- then hold down the power button for 25 seconds in order to completely discharge the capacitors, etc.

Try plugging in the AC power and attempt to boot. If nothing happens, then repeat the process but run off of the battery instead (no AC adapter).

gb_ibmguy · #5 Post by **gb_ibmguy** » Mon May 11, 2009 9:22 am

I’ll give that a shot when I get home, thanks!
I did succeed in getting it to boot running off just the known good battery.
What I can’t figure is why the port replicator can’t / won’t supply AC power to the unit. I’ve tried all 3 of my power supplies and since the replicator tested good against the other A31, I know it is not at fault. I would hate to go to the hassle of replacing the power receptor on the MOBO only to find that there is some other problem in the power circuit.

gb_ibmguy · #6 Post by **gb_ibmguy** » Thu May 14, 2009 4:12 pm

Ok,

I have my A31 reduced to many pieces and parts (all labeled and bagged). I just received the replacement power jack and am going to solder it in tomorrow. Now, is there any way to test the jack, once installed, and the motherboard before I rebuild it? Can I screw the MOBO back into the base housing (without anything else attached), apply power and OHM it out? And if I can, what voltages am I looking for and in what locations?
Any insight from anyone that has tested a ThinkPad MOBO would be appreciated.

#7 Post by **rkawakami** » Thu May 14, 2009 4:32 pm

About the only thing you can do after soldering on the new DC power jack and before applying any power to the system would be to check for continuity (i.e., ohm out) from both the center pin of the jack and the outer ground shield, to the board that it's mounted on. The best places to select on the motherboard for the ohmmeter probe would be at the soldered connections. You should also check to see if there's a short (0 ohms) between the center pin and ground. The easiest place to pick off system ground would be one of the studs on the VGA or parallel port. If you put the ohmmeter into a resistance range of Kohms or Mohms, you should see a changing resistance display (increasing towards infinity) when connected to the center pin and ground. That's a sign that the capacitors in the input power circuit are charging. If you see 0 ohms, then you have a short and you shouldn't connect any power until you find and fix the short.

However, reading your earlier description on how the system does not power up when attached to a port replicator seems to me to be more of a general problem with the power conditioning circuit(s) on the motherboard, then with the a problem with just the DC power jack. More likely, you have a blown fuse or damage to the power controller(s).

Can't give you any hints as to what voltages to measure and where since circuit schematics are not available. I've been able to power up T23 motherboards mounted into the base, with only the heatsink/fan assembly in place by attaching the system to a port replicator and using the power button on the port rep to power on the system.

gb_ibmguy · #8 Post by **gb_ibmguy** » Fri May 15, 2009 7:06 pm

WoooHeee, I'm back in business!!!!

I had my good friend at work solder the new jack in today and he checked out all the fuses (thanks to the diagram found here). He pronounced all the fuses he could find good. So I proceeded to rebuild the laptop, thinking all the time that I would probably need to do this all again with a new motherboard. Low and Behold, when I applied power, the darn thing booted up! It's charging the battery right now! All is well!!!
Ray, and everyone else here, thank you very much for your help and thoughts! Once again, this group is the best!!

PS - Next test is to see if this thing will work with the port replicator - still odd that it didn't but for now, I'm happy!!!

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