edit again lol: reading here it says :"Response from caps lock key means CIA and the CPU works.[5]"
http://en.wikipedia.org/wiki/Kickstart_%28Amiga%29
So if pressing it on and off and light goes on and off does that mean the cpu still works?
Whoever wrote that Wikipedia detail based on my
article seems to have misinterpreted what I wrote. I've since updated the Wikipedia page as follows:
"When the caps lock key is repeatedly pressed approx. 10 times, the caps lock LED turning on and off each time indicates the CPU is correctly reading the CIAs. If the caps lock LED sticks on or off, the CPU is not servicing CIA interrupt requests."
Feel free to re-word things if I've made an arse of explaining it.
Looks like your A3000 has some fundamental hardware issue going on. The next easiest thing to do is look at the /ROMEN line (active low) to see if the CPU is at least attempting to access the ROMs and that the system address decoder is working. You'll need an oscilloscope for this, or you might get a rough idea by using a logic probe.
If /ROMEN has no activity, you'll need to look closer at the CPU support and control. e.g. make sure reset is high, all system clocks and clock dividers are working normally.
If you have OS2.x or 3.x in ROM and the Zorro riser card is not fitted, the CPU will generate an exception (yellow screen), but that happens quite a bit later during ROM execution; I think when expansion.library gets called. Most of the hardware will need to be working for it to get this far.
Since the system was working before you replaced the battery, you've probably disturbed something. Often this is caused by dodgy IC sockets. Did you check for corrosion in the Densie/Paula sockets? (green/blue terminals)
