T20 Hangs on AC w/batteries installed

[bretski]

Hi from a thinkpads.com newb!

My faithful 7-year old T20 is starting to give me problems. Over the past few weeks, I've been experiencing (what I thought to be) random hangs. After a bit of trial and error, I have narrowed it down:

The machine works fine on battery power. It also will work fine on AC power, as long as no batteries are installed. However, if the AC is connected while running on battery power, the machine will hang within seconds, usually almost immediately. I can replicate this issue consistently with all battery installation configurations (main and ultrabay, main only, ultrabay only).

Has anyone experienced a problem like this? I'm concerned that this may be a system board issue...

I love my thinkpad! Please help me save it!

[Harryc]

Have you tried a different battery?

[bretski]

Have you tried a different battery?

Yes, behavior is exhibited with both the ultrabay battery and the main battery bays, all combinations.

[SMA]

It does not have to be a system board issue. It could also be the AC Adapter. And the AC Adapter is a lot easier to test, if only you can find one to test with. If you do not have one extra, then you may try to borrow one from someone, somewhere. Just remember to check its specifications before plugging it in. It must be able to supply 16V and at least 3.36A, center positive.

[rkawakami]

Just remember to check its specifications before plugging it in. It must be able to supply 16V and at least 3.36A, center positive.

Ah, check the bottom of the T20 system. I think it will say 4.5A, not 3.36A. At least that's what it implies in the tawbook. This translates to a 72 watt AC adapter not the 56 watt one.

[bretski]

Bottom of the T20 says 16V, 3.36A. I will dig out my voltmeter and test right now...

edit:
The AC adapter is putting out 16.54 volts. This is in spec, according to the hardware maintenance manual. Any other ideas???

[BillP]

Before deciding the adapter is good you need to check the voltage at full load. Also set the meter to AC and verify that the reading is very low. You ideally want pure DC with as little AC ripple as possible.

Your symptoms point to the AC adapter since the heaviest load occurs when the battery is in place, assuming it is charging (or trying to).

You should be able to find a 4.5A adapter on Ebay and it just might fix the problem.

[rkawakami]

For that you would need to build yourself a little cable to plug between the laptop and AC adapter, as there's no easy way to measure the voltage at the DC plug when it's plugged into the system (and without opening up the laptop or breaking the insulation of the DC cord).

[bretski]

Well, I'm going to try a different adapter. Just got one off of ebay. Crossing my fingers that this will do the trick. Will update when it arrives...

Thanks for the help so far!

[bretski]

I received the new (to me) AC adapter today. Booted the machine on battery power, plugged in the AC, and walked away. Came back in 5 minutes or so, and the machine was locked-up tight. grrrrrrr.

So am I looking at a new system board, or are there any other troubleshooting steps that I can take?

[rkawakami]

Best thing I can suggest is to de-populate the machine to the bare minimum (one memory module). This means remove the hard drive, Ultrabay device, MiniPCI card and make sure everything is unplugged from the PCMCIA and USB ports. Get a copy of memtest86+ and run it for at least three complete passes. If you have a second memory module, swap it out with the first one (and use the same slot) and run memtest86+ again. If all your modules pass, then install them into the second memory slot and repeat. What you are looking for is a failure of a certain module and/or a specific memory slot. Assuming that all of the memory testing reveals no problems, then get a copy of PC Doctor as outlined in this thread and start running the tests under the Diagnostics group. Start with CPU/Coprocessor, then Systemboard. Prior to running any one of the tests press the F2 key and change the "Pass Count" value from the default of "1" (single pass) to something like "50". This will force the diags to loop that many times.

[bretski]

Thanks, Ray. I'll give that a try. Stupid question:

What should I boot memtest86+ from if I'm stripping the machine down?

[rkawakami]

Oh, sorry... I usually use an external floppy . If you don't have a port replicator and external floppy (or an Ultrabay floppy), then burn the .ISO and boot from the CD.

[bretski]

No prob, I figured you were thinking floppy. I do have one (will have to blow off some cobwebs), and will hook it up to my port replicator.

[rkawakami]

BTW, run all of the diagnostics *without* any battery installed. From your previous descriptions, this should at least let the system boot and run for several minutes.