Amiga 3000/16mhz woes...

[Ilwrath]

I was going through my Amiga inventory and sorting out some odds and ends to sell off, when I met back up with an Amiga 3000 that had perplexed me enough that I shelved it.  

Here's the rig-
It's a 16mhz Rev 9 A3000 desktop.  
Standard configuration, with the exception of 3.1 ROMS (ver 40.68)  

Here's what it does-
Turn on the power...  
HD spins up normally.
Power light comes on at normal low-brightness level.
no HD light activity.  
Keyboard caps lock flashes one, video outputs a black screen.  
CTRL-Amiga-Amiga sends a reset to the HD (you can hear the HD make the same click as when it first spins up) and the keyboard caps lock flashes once again.  Video never changes from the stable black screen.

Here's what I've checked-
Confirmed all jumpers set to 16mhz INTERNAL clock for both mainboard and CPU.
Set ROM speed jumper to slower access, in case system was unable to read ROMS. -- no change
Swapped ROMS for an A3000 set of 2.04 ROMS -- no change.
Removed fast mem -- no change.
Reseated all chips -- no change.

I'm stumped.  I'm used to getting some kind of screen activity or hint as to what's wrong....  Any ideas, suggestions, folks?

[Ilwrath]

Does the LED turn on and off when you press caps lock? If so it indicates that there is some CPU activity.

It will for about the first 5 seconds, or so.  Then it'll stay off.  Almost like the system hangs VERY early on.

Does the power LED change between 2 brightness levels just after power up? This is in the computer's power up sequence.

No, comes on on the dim setting, stays dim.  never flashes bright.

Sounds like it's running through the power up sequence, so there could be a problem with the CPU itself, or any of the custom logic like Gary.

Yeah... This one was my fear.  I'm wondering if I should try a CPU card in the fast slot to try to bring the system up.  Does an A3000 still need the system CPU if it has a CPU card in the fast slot?

As suggested, reseat all socketed devices first.

(already did.  thought I wrote that in the already tried column.  Far from my first miggy I've torn up.  ;-)  )

You're possibly a bit stuck without access to known working spare parts and some test equipment.

Also my fear.  Thanks, though.  :-)

[Ilwrath]

One of the programable logic devices U202, U203, U701, U714 could also be faulty.

Hmm......  Quick test with the accurate measuring tool of my fingertip.....  U714 is warmer than the others.  ;-)

Where would I locate a new U714, nowadays?  Red?  :-)

[Ilwrath]

I have a 390529-03 -- it's printed on a silver C= sticker.

I doubt that part is on an A500... I was going to check my part-scavenged machine, but it's in the back of the closet, and I haven't gotten to it, yet.