A3000 problems, CPU+ROM

[Tenacious]

It's tough to imagine how shipping could lift a pin and re-solder it in a new location.  Is it soldered down?

Do you have schematics or info on the net to reveal what signals are on those 2 pins?

When you received the A3000, did you find a loose, heavy component that could have gouged the pin up?  Was there other damage?

If the pin is soldered in that location, it must be a purposeful modification, either by the manufacturer or a previous owner.  I' m not aware of this mod (nor a lot of stuff, grin).  OTOH, I believe there were several rom configurations over the 3000's production run.  I wonder if this mod could be related.

Found it!  According to my schematic, if CPU is SMD (surface mount device, ?), pins 1,2,5, etc are grounds.


I believe that only early 3000s had rom towers. I think the towers were used to accommodate roms with different pinouts. On later MBs, the roms were socketed directly on the MB.  Can the tower be installed differently than it is? Did you remove it and forget?

[Tenacious]

Someone correct me if I'm wrong.  It appears that pins 1 and 2 are soldered together. According to the schematic I saw, they are connected together to ground.  You can varify this with an ohmmeter to any known ground point.  IIRC, chip pins are numbered counter-clockwise beginning with the pin 1 indication.

It is, of course, your motherboard and your risk.  I'll bet the pins were soldered together at the factory, though. Most shade-tree tinkerers steer clear of surface mount modifications.  What motivation would the previous owner have for sabitaging your board this way?

[Tenacious]

I had a 3000 with a rom tower 10 years ago.  Commodore seems to have been creative with this.  I believe one class of roms fit the tower, another class (same number of pins but different pin-outs) fit directly on the motherboard.  This is supposition on my part.  When I wanted to upgrade the rom, Software Hut was very knowlegable about the different rom variations Commodore allowed for.  Amigakit may also have info about this.

You bought the MB alone or in a case?  

Your concerns:  1.  The tower can be rotated 180 degrees and still fit the MB?  2.  There are 4 empty sockets on the MB and the legs from the tower can fit in 2 different pairs?

Can you find any photos of the MB with the tower installed?

[Tenacious]

Another thought: are there any marks or silk screens on the bottom of the tower to indicate which sockets it goes into?  On the top of the tower?  What about the MB, an outline of the tower maybe?

[Tenacious]

This all sounds correct.

@Orange

There are some cross-checks you can make with a multimeter to remove most of the risk.  Try to identify those traces on the tower and MB that carry +5 volts and Ground.  If they are not marked, look for a polarized capacitor on the tower.  The lead marked + will go to 5 volts, the - lead to ground.   Bare in mind that the MB also has polarized capacitors for +/- 12 volts too, make sure you've identified +5 volts on the MB!

With the tower plugged into the mother board, there should be continuity from +5 volts on the MB to +5 volts on the tower.  Same for the grounds.  It should not matter for this test what  pair of rom sockets the tower is plugged into.  This will determine orientation of the tower.

I think Zac is right about the upper pair of sockets.  You should be able to install the tower and power up.  If the 3000 doesn't boot, the addressing is likely wrong.  This is probably not a fatal test.  Try the lower pair next.

That's as good as I have so far.  If you're still uncomfortable, wait for better knowledge or another brain storm.

Good Luck!

[Tenacious]

Congrats!

IIRC, the first 3000s came with roms to get to a Kickstart select screen, sort of in the style of the A1000.  The actual rom image was on the HD.  This dates from when OS 2.x was still in development.  You probably have an original!

Later, when OS 3.x came out, many ppl replaced these loader roms with rom chips containing the complete Kickstart (like most other models and the later 3000s).  This is where the confusion begins. There was a special Kickstart 3.1 rom set for your MB rev and tower.

I never pursued this, but, I think some people were able to obtain a KS 3.1 image file.  They could leave their machines as originally made AND have the flexibility to boot into whatever version of Kickstart they wanted.