I have an A20m (2628-4UU) that failed last evening with the same
symptoms that literally hundreds of others have reported over the last
few years. Mine had been running fine, but I went to power it up and,
once it got to the Windows desktop it froze. Powered off, then tried
powering on again. Unit comes on when power is pressed (HD spins up,
all lights flash on, then go off except for power, I can hear the CPU
fan running). No POST, no boot, black screen.

I replaced the CMOS battery, reseated everything, yada yada yada. The
thinkpads.com web forums list a possible cause as a failure of one (or
both) chips in the dc-dc power section on the mainboard. These are
the Analog Devices ADP3421JRU and ADP3410KRU ICs. This is supposedly
due to a design flaw. Some people also say to change three MOSFETs
(IRF-7811) as well. Some report success, others don't.

It seems to me that by simply replacing the chips you're not fixing
the problem. SOMETHING caused the chips to fail as there wasn't (to
my knowledge, anyway) a bad run of those chips. Bad capacitors in the
circuit, maybe? Bad resistors, diodes ...? People ARE apparantly
fixing the boards, as dealers will sell you refurbished ones or will
fix your broken unit.

So, what's the secret? Which components are routinely replaced during
the course of one of these repair jobs?


On Thu, 27 Jul 2006 18:13:12 -0400, Rick <rickajho@rcn.com> wrote:

>Hi
>
>Thinkpad A21m in this case, but apparently the problem isn't limited in
>the IBM line.
>
>Left the unit unplugged & unused for a couple months. Plugged it in, hit
>the power button... nothing. Well, almost nothing. The only thing that
>happens is the battery charge indicator lights, and the bank of 5 green
>status LED's light. Then all of the status LED's go out except the one
>of the far right. (I can't even tell what that symbol is supposed to
>mean.) No post BEEP code, no video, nothing...
>
>Tried it with the battery pulled using the AC adapter only, a fully
>charged battery with the AC adapter, a fully charged battery without the
>AC adapter... no change.
>
>A Google search on this provides several hits about the same problem on
>several ThinkPad models, but no clear indication what the problem really
>is. I've seen speculation that it's a dead CMOS battery - which some
>people changed and didn't help. An "overcharged capacitor" - which
>putting the computer in the 'fridge is supposed to help. (???) A glitch
>in the IBM BIOS regarding the suspend operation...
>
>Anyone really know what the problem is and what to do?
>
>Rick
** To respond, remove the crap from my addy... **