Replace CPU or logic board first?

Hello everyone,

So, i bought a PowerBook g3 off ebay for $30 (dvd, 512Ram, no hard drive, 400mhz lombard) as-is, and i find out it has some sort of a hardware problem, but i still have no charger, so i take it back and forth to the Apple store. Ive eliminated all the problem parts except the CPU and the Logic Board/Power board or whatever.....
You can see the full thread on the apple discussion board here:

http://discussions.apple.com/thread.jspa?threadID=1134524&tstart=0

So, which should i replace first? Im thinking CPU, because a person on the apple thread said that the same thing happened to him too, and a cpu did the trick. Will a cheaper/slower cpu out of a wallstreet work? Is there any sites where i can get a CPU and return it if that is not the problem?
Advice?
Thanks,
Tanner.

Processor

Hard to say...there are a lot of issues with processors. From my experience, I replaced a 333 with a 333 and it worked like a charm. You sure the RAM is okay? I've seen a lot of issues with that. If you have a 133 RAM chip in there, it could cause issues.

I picked up an entire system on eBay (w/ processor) for like $50 and it worked. Keep your eyes peeled for a used processor 333 or 400.