One for the german tank algorithm ![:wink:]( "Wink")
This is jbredcar's beast. Board was fairly filthy, so I took quite some time gently cleaning it all with an ESD-safe brush and cotton-bud.
The board is, surpisingly, exactly the same form factor as an A400/1 it seems:so why Acorn made a whole new terrible case for the A680, who knows! Even the unpopulated keyboard connector position looks like it would perfectly suit an Archimedes case (it's panel-mount on the A680).
The dual MEMCs are a great interest to me...I'd love to see the markings, but daren't (yet...) try and work out how to unclip these things.
After measuring various points to ground and rail to rail and doing close visual checks, no obvious problems show up so, gulp, let's power it up from a bench supply. And fail. My standard wee bench supply can only give 3.1A and this board sucks more than that! That's crazy. A fully-loaded 16MB A540 only draws about 2.5A. The thermal camera gives some good hints as to where all that power's going though - within just 2-3 seconds of power-up, all the PALs, the floppy controller, and the RS232 chip are quite aglow:The onboard diagnostic LED display shows 0,3,4 and by that time the supply's decided it's had enough.
So right now, I'm not sure if that's just normal, and why the A680 has such beeeefy power cabling, or if it indicates something unusual about this particular board.
I do think I've since found an issue though...I think there may be some PCB damage here and where's IC6 gone?! All other A680 board photos I can find online show IC6 present - it appears to be a rather important part of the hires-mono circuit -- which is unfortunately the only video output that the A680 has! Why, Acorn, why? No RGB. And no audio (only internal speaker).
So I do think it's probably a good idea to check all the tracks in this area of the board and fit a fresh IC6 before proceeding any further - because without any video output, I'm not going to be able to do a lot with this board anyway. It's a 74F00, performing the same job as the IC3 74S00 on an A400/1 - I wonder if F speed vs S is particularly critical - will get one ordered up anyway!
There's a bunch of patch-wires on the back of the board and these all appear to be the same as seen on other A680 boards, but I'd like to understand them all and document them. For now, there's a bodge wire on the top side, which most (but not all) other A680s have - it's quite simple;
This is jbredcar's beast. Board was fairly filthy, so I took quite some time gently cleaning it all with an ESD-safe brush and cotton-bud.
The board is, surpisingly, exactly the same form factor as an A400/1 it seems:so why Acorn made a whole new terrible case for the A680, who knows! Even the unpopulated keyboard connector position looks like it would perfectly suit an Archimedes case (it's panel-mount on the A680).
The dual MEMCs are a great interest to me...I'd love to see the markings, but daren't (yet...) try and work out how to unclip these things.
After measuring various points to ground and rail to rail and doing close visual checks, no obvious problems show up so, gulp, let's power it up from a bench supply. And fail. My standard wee bench supply can only give 3.1A and this board sucks more than that! That's crazy. A fully-loaded 16MB A540 only draws about 2.5A. The thermal camera gives some good hints as to where all that power's going though - within just 2-3 seconds of power-up, all the PALs, the floppy controller, and the RS232 chip are quite aglow:The onboard diagnostic LED display shows 0,3,4 and by that time the supply's decided it's had enough.
So right now, I'm not sure if that's just normal, and why the A680 has such beeeefy power cabling, or if it indicates something unusual about this particular board.
I do think I've since found an issue though...I think there may be some PCB damage here and where's IC6 gone?! All other A680 board photos I can find online show IC6 present - it appears to be a rather important part of the hires-mono circuit -- which is unfortunately the only video output that the A680 has! Why, Acorn, why? No RGB. And no audio (only internal speaker).
So I do think it's probably a good idea to check all the tracks in this area of the board and fit a fresh IC6 before proceeding any further - because without any video output, I'm not going to be able to do a lot with this board anyway. It's a 74F00, performing the same job as the IC3 74S00 on an A400/1 - I wonder if F speed vs S is particularly critical - will get one ordered up anyway!
There's a bunch of patch-wires on the back of the board and these all appear to be the same as seen on other A680 boards, but I'd like to understand them all and document them. For now, there's a bodge wire on the top side, which most (but not all) other A680s have - it's quite simple;
Statistics: Posted by IanJeffray — Tue Feb 18, 2025 12:48 am