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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: orange on June 23, 2008, 08:19:16 AM
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I got an A3000 that is in bad shape (probably shipping caused it :( ).
The CPU has deformed pin1:
photo1 (http://www.fileden.com/files/2007/6/28/1218776/Amiga/up_IMG_1392.jpg)
photo2 (http://www.fileden.com/files/2007/6/28/1218776/Amiga/up_IMG_1403.jpg)
photo3 (http://www.fileden.com/files/2007/6/28/1218776/Amiga/up_IMG_1406.jpg)
that pin is welded to one on its left side (tested with multimeter).
should I try to separate them before turning on A3000?
Which way is the ROM tower oriented, and in what set of sockets does it go?
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I'd look up the pinout for that chip and see if those pins can be connected without breaking anything.. but I reckon it'd be pretty easy to separate the pins with a craft knife.
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so they should be separated? all A3000 motherboard photos on big book suggest that is the case.
what about the ROM tower? is this (http://www.amiga-hardware.com/download_photos/a3000rev70.jpg) correct?
I found some old posts that say there are different versions, with various orientation
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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?
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DO NOT TURN ON YOUR AMIGA 3000 UNTIL YOU SEPARATE THE PINS OF THE CPU!!!
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Re ROM tower: On the tower PCB pin 1 should be a square solder point. Also, when the socket notch points upward, pin 1 is the top left one (device side that is).
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thanks for replies.
The ROM tower came loose in shipping, maybe it hit the CPU.
The two pins on CPU (first and last one) are definitely soldered together. I tried separating them but its tough.
Only desoldering with solder wick/braid might do it but its risky.
It seems unlikely to me that it was never before powered on with those pins connected together, but I'll separate them.
BTW, motherboard is v6.3 and ROM tower is v1.
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Eh? Did you read above??
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er.. yes?
It's tough to imagine how shipping could lift a pin and re-solder it in a new location. Is it soldered down?
I agree, but deformation might be caused by a blow. Is what soldered down? CPU-yes. the pins together-yes.
Do you have schematics or info on the net to reveal what signals are on those 2 pins?
According to my schematic, if CPU is SMD (surface mount device, ?), pins 1,2,5, etc are grounds.
I couldn't find any pinouts. What does your schematic say about last pin? (because I believe that one is soldered to pin1). EDIT: wait, I don't know which way numbering goes, so it might be pins 1 and 2 are connected? then its OK?
If the pin is soldered in that location, it must be a purposeful modification
but it could be someone dropping the soldering iron there, anyway:
DO NOT TURN ON YOUR AMIGA 3000 UNTIL YOU SEPARATE THE PINS OF THE CPU!!!
Can the tower be installed differently than it is? Did you remove it and forget?
yes there is a pair of slots so 4 combinations; it was 'removed' in shipping
On the tower PCB pin 1 should be a square solder point. Also, when the socket notch points upward, pin 1 is the top left one (device side that is).
I'm not sure if I understand this, is the ROM chip pin1 on same side as socket pin1 (away from keyboard connector).. rom tower goes into U182, and U183?
(I gave you my ROM tower version because some say it matters.)
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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?
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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?
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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?
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The shorted pins are 1&2 (they count counter-clockwise from the notch) and are both GND, so nothing to worry about apart from cosmetics.
I was talking about the ROM tower orientation: the connector to the mainboard is soldered to the tower's PCB. One pin (pin 1) should have a square solder point (or differing some other way from the rest) - this one is to be oriented towards the side where the mainboard socket's notch is.
In addition, the two ROMs 'hanging' on the ROM tower also have notches or a blank spot indicating pin 1 (as might the socket used for gaining height). Everything I've ever seen shows the tower goes to the two topmost sockets (U182/183).
And yes, the tower ROMs do seem to differ from the ones that go directly to the mainboard. I can't confirm this from my own experience, but I've heard it several times. Apparently you can't use 'mainboard' ROMs on mainboard revs that use a ROM tower.
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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!
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I did it (leaving CPU as is), and it works great.. :banana:
(like you said, the ROM socket on tower does have the square pin 1)
After boot there is a menu with choice of ROM (1.3 or 2.x)
The only small problem left is that I'll need some sort of cradle for hard disk, I don't see a way or place for mounting it now.
Also the battery needs replacing, the usual LithBatt.lha should do it?
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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.
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Tenacious wrote:
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.
Yup, even a noob like me was able to get this working on my softkick 3000.