Replaced DC-in board but ibook still won't work??

Here is the link to Apple's Knowledge Base article on troubleshooting portable that won't turn on or start up:
http://docs.info.apple.com/article.html?artnum=50959

You never mentioned the colored lines before.

It sounds like you may be having logic board problems. Enough Dual USB G3 iBooks suffered from the logic board problem that Apple began the iBook Logic Board Repair Extension Program in January of 2004. Check out the FAQ page and if the symptoms look familiar, give Apple a call. If the iBook qualifies, it's a free fix.

You can find the original purchase date of the iBook, by entering its serial number into the box toward the bottom right of Apple's main support page under "About Your Support Coverage."

If it is past the three-year time limit (which it probably is), try calling Apple at (800) 767-2775 and ask for Customer Relations (NOT Customer Service--they can't help you) and ask them to please make an exception to the three-year limit in your case.

If the answer from Apple is absolutely, positively, "NO!" you may want to consider trying the shim fix suggested by John Sawyer in the Apple Discussions iBook G3 (Dual USB) Displays Forum:

[Y]ou can often fix this yourself by removing the iBook's bottom housing, and placing a shim of any sort, about 1mm to 1.5mm thick, onto the raised square on the bottom shield. I use a Scotch mounting square--you can get them in hardware stores and many grocery stores. When you reinstall the bottom case, it will press against this shim, which will press against the graphics chip, and may allow the chip to come into better contact with the logic board.
John Sawyer
CJS Macintosh Repair

Instructions for removing the lower case:

iFixit.com

If Apple doesn't come through, and the shim fix doesn't work (or you're leery of trying it), DT & T Computer Services in Fremont, California offers the cheapest repair I've found. They have a six-month warranty on the repair.

Once you get it fixed, try never to pick it up by the left front corner alone. Rumor has it that can contribute to logic board failure when the case flexes, causing the graphics chip to come loose from the logic board. If you're picking it up in your left hand (as I often do mine), pick it up in the center under the trackpad.

Good luck.

On this side of The Pond, DT & T Computer Services will repair or replace the logic board for $195, which is less than you will likely have to pay for a logic board on its own.

I'm not certain about whether you can upgrade to another G3 logic board or not. I can't recall reading about anyone getting that done.

Let us know how things go.

the logic board in my ibook died a few mnths ago and i managed to get it working using the "shim" fix with about 6 business cards. I live in the UK and found that a logic board for my (currently broken, though for unrelated reasons - i spilled juice all over it) ibook would cost in excess of £300, almost what I payed for my ibook in the first place