I fixed the battery charger and had it working perfectly but noticed that all the RAM was not being used. Read about the bad socket, so I re-soldered it. Must have had a short somewhere but fixed it. Now, it won't boot and sometimes gives the 4444 beep sequence. After all this work, I hate to junk it. I like the computer. Any suggestions?

Motherboard replacement comes to mind.

I tried to re-solder the T30 RAM sockets once....must have made a solder bridge...'cause as soon as I tried to power it up, it burned a hole in a motherboard chip. Probably not exactly the same with yours, but I wouldn't be surprised to find something similar.

Thanks for the quick answers. I didn't see any smoke or smell a burned part. Maybe I will dis-assemble it again - a real pain, and look for something. Thought it might have damaged one of the power supplies, but checked them and both the 3.3V and 5V supplies are ok.

Are we talking about a T30 laptop or some other desktop?
3V and 5V do not come from the laptop's power supply...

I got the schematic from China. There are several switching supplies on the motherboard. From the 16V input, they generate 3V, 5V, the CPU voltage and 2.5V for the Memory chips. They are all ok on my pc, so I am not sure what is causing the problem. Something else must have gotten damaged.

4x4 beep sequence is related to the security chip.

A *very* bad sign in my experience.

If the unit has one of those old removable security chips, take it off and then put it back on the board. It might do the trick. If it doesn't, you're looking at a planar swap.

Good luck.

Unfortunately, you are right. Removed the security chip and put it back. Now it is completely dead. Not even a beep.
Will get another MB. Am getting pretty good at dis-assembling and re-assembling this thing.

As RBS has advised me in the past (as I am defiantly typing this reply on my T30)...

The T30's ATI Mobility Radeon 7500 video controller with 16 MB graphics memory is simply unable to keep pace with the graphics and video found on today's modern websites.

Your time would be better spent on purchasing a 4:3 standard aspect R61/T61 with integrated Intel graphics,
(i.e. Mobile Intel(R) 965 Express Chipset), while they are still available.