T42 won't power on without a battery present

[laboye]

I just received this puppy in the mail. Aside from needing a reflow and the issue described here, it works great. My first power-on test looked ok. It didn't have a battery and booted happily. I gave it some taps, bumps and jerks to test the GPU and as expected, the display went out. I turned it off and back on; no video. I did the same thing again, but with pressure on the GPU and it worked fine. On the fourth try (trying to see how badly it is damaged), I powered it up with no GPU pressure. The power light flashed and I *think* I head a small click sound. Thereafter, it would not power up at all. No lights or signs of life. A different AC adapter produced the same results. I popped in a good battery and removed the AC adapter and it powered up fine (with GPU pressure applied, of course). With the machine off and both the battery and AC power present, the charge indicator comes on as normal. It also powers up fine with both present. Basically, all is well until the battery is removed.

Given the circumstances (especially that click), I think its one of these fuses I've been dreading so much. I'd like know what can cause this problem and if possible, what's the fix?

TLDR: The system shows no lifesigns whatsoever unless a battery is present. Fuse? Ideas?

[Harryc]

I would also guess a fuse has blown given your description of the symptoms.

[laboye]

Hi. I scoured the system's fuses and found that 'F2' looks shot. In the Fuse Locations PDF, F2 is 'DC In Main Fuse 16V', a 7A fuse. Strangely enough, I'm using regulation IBM 4.5A AC adapters off of a UPS, so I don't see how it could have blown unless it was simply its day. I took a macro pic of it; tell me what you guys think.

http://taconet.net/t42fuse.jpg

If this is the case, where can I get these fuses? Is it just a matter of soldering the new one on?

-Eddie

[Harryc]

You can't tell if it's blown unless you measure resistance across it with a multimeter..an open is zero ohms.

[rkawakami]

Uh, an "open" is infinity ohms. A good fuse will read 0 ohms. You can generally order these Littelfuse components from either mouser.com or digikey.com. If the original fuse is really blown, one possible way to install a good one is to solder it directly to the top of the old one. You might have to put a fair amount of solder on the ends in order for it to flow down to the lower fuse's endcaps.

ref: http://forum.thinkpads.com/viewtopic.ph ... 44#p406644

[Harryc]

Ray, thanks for the correction. It's been awhile since I had a multimeter out or had to think about ohms.