DiagROM

I have been trying to fix the Amiga 2000 with the battery leak shown earlier.  I ended up with two.  The one I thought might be unsalvageabe (I had to replace the socket for the Gary chip too) works fine.  The one pictured not so much.  I get a light grey to dark grey and back flashing screen on Kickstart 1.3 and yellow on KS 3.1 and 2.05.

What to do?  I followed some old trouble shooting guides to no avail and beeped out dozens of motherboard traces.  All fine.  I even swapped out a bunch of parts including Agnus and a few CPUs.

Next I wrote a DiagROM.  A replacement diagnostic ROM available here: http://www.diagrom.com/  Writing Amiga ROMs is not so easy, I have a minipro programmer but a special adapter board is required.  I bought one from GGLabs and soldered my own parts to it.

GGLabs do a flash memory based Amiga ROM replacement too but I have a UV eraser.

The DiagROM booted to a GUI!  Sadly (happily?) the computer passed all the tests. Check it out:

If you use DiagROM throw John some beer money, he has forged a custom tool and is making it available for free.

More to come.

Amiga Tank Mouse Buttons

Changing these is a piece of cake.  A bit of desoldering braid and a couple of SP0600 switches from Jaycar.  All is clicky again 🙂  They go in with their legs the same way around as the originals.  Most of the work was cleaning (mouse grime is revolting).

I used lead solder given that was almost certainly what was there originally and it is stronger I am told.

Amiga A2000 battery damage repair

I recently acquired an A2000 with a Genlock (for what use I cannot say, will mean I need to keep at least one A2000 PSU with its ‘tick’ signal up and running) and 8MB RAM card (four installed).  I have not tested the cards, first I am going to work on the motherboard.

As with most old A2000s the NiCd battery has leaked.  This one was stored on its end and the corrosive goo has dripped into the CPU socket.

If you look at the socket, the four holes closest to the battery show some green colouring (hard to see but it is visible in the photo), the matching legs on the CPU are not shiny either. I am yet to find any corroded through tracks though (using a multimeter) which is good.  This may in part be because the goo went over to the CPU socket rather than sitting on the board.

I have an untested hypothesis that powering one of these machines up after a long period of inactivity can bring on failure.  The person I got it from said it worked at last power up, I believe him.  However, while it was on the computer would have tried to charge the battery. I think this will often be a cause of total failure.

Anyway, reseating the CPU did not fix the problem.  This could be due to the corrosion inside the socket being too deep to get scratched away.  It could also be that the goo has worked its way through the board and created ‘cold’ solder joints (I have revived an A500 RAM expansion by, in part, resoldering goo affected pads that looked OK.)

I have some new 64 pin 2.54mm spacing sockets coming from Germany from ebay, will be fun desoldering and replacing the CPU socket!  I think I also need to finally set up a firm barrier between lead free and leaded soldering to get this all done right now and in the future (I do my new work lead free and often tin and re-tin old stuff to remove the lead then go lead free).  These old boards are not something I want to heat more than absolutely necessary.

Rack mount Amiga 1200

Six weeks ago I bought an Amiga 1200 on ebay.  It had been fitted into a custom cut rack mount case (it even exposes the PCMCIA slot) and had been used by the seller as a graphics server of some kind.

EDIT: I recently learned more about the previous life of this 1200.  Older hotel systems had TVs that had RF in for a bunch of channels but they were not standard channels.  They were rebroadcasts of local channels (or something) plus various movie channels perhaps rebroadcast from cable TV.  One of the channels usually had a welcome to the hotel and bragged about room service and local attractions.  This Amiga served that slideshow.  They did so for many many years.  I think I bought mine shortly after it was decommissioned.  When I recapped the machine recently it was in good shape (the rack case has good cooling and the seller said it was always operating in an air-conditioned environment) except for one capacitor that had leaked, I subsequently read it was for the circuit that combined audio and composite video for the RF output, it had a hard life.  I also found suggestions that the manufacturers of the cases were in England bought boards directly from Escom/Commodore for these setups.

It came with nothing but the case, floppy drive and the motherboard.  Also there was a heatsink on Alice (an update to Agnes for the AGA graphics chipset present on the A4000, A1200 and CD32.)  The heat-sink on Alice was not well attached and small.  I knew I would be adding an Individual Computers AGA MK2 flicker fixer which would only put more load on Alice (even Individual Computers says so) so I took a photo of it (her?) and  then used thermally conductive epoxy to attach a nice gold HS that had been a South bridge heatsink on a Pentium4.  I will probably print the photo and stick a picture of the installed Alice inside the case should the model number matter one day.

I added the flicker fixer and passed its DVI connector, having machined it down to fit between the power connector and the composite connector and around some capacitors, through an existing hole in the case that was for the analogue TV out (which I desoldered and removed).  Some RF shield trimming was also involved.  Double sided tape holds the connector to the motherboard.  It was just the right thickness as the pictures show.

I then added a PC-Key 1200 keyboard adapter (with an extension cable I soldered in).  I had to remove the plastic retaining clip from the top of the keyboard ribbon cable socket and it just pushed in.  I chose this part because it came with a standard chassis mount socket, goes into the keyboard slot instead of clipping over an IC and supports both PC and Amiga keyboards.  The Individual Computers part which I seriously considered (Lyra 2) does not support Amiga keyboards and has a PCI slot backplate instead of the chassis mount socket.  It does however support more than three simultaneous key presses which the PC-Key does not.

I also added a short IDE cable to a dual Compact Flash adapter from ebay, an original A1200 power, floppy and HDD light (I had to file the case behind the fascia for this, the original machining was not right and the original owner never put the LEDs in) and a nice A1200 label for the front (also from ebay).

Finally, after adding some nylon bolts to support the card up off the bottom of the case, I plugged in an ACA1233n with battery backed up clock (thanks Amiga Kit for fitting the RTC module prior to shipping).  It adds a 68030 and 130meg or so of RAM.  Considering the A1200 shipped with 2meg, this is quite a lot.

Lucky last, I installed classic workbench using a guide on YouTube (thanks dude) and set up some WHDLoad demos and stuff.  I must say though, having used the state-of-the-art Workbench I am thinking about going back to a more basic version that better suits my A2000 nostalgia.

There were a few hiccups installing the AGA flicker fixer drivers, I didn’t realise that ‘1.1’ software had to be installed first based on the available information.  For some reason too, the guides to installation say type ‘install’ to run the script that copies everything un-lha’ed (to a RAM disk when you have as much as me) to the right spots.  I somehow remembered, when it didn’t work, to enter ‘execute install’.  That did the trick.  The flicker fixer is an impressive piece of hardware.  I am always surprised by how much new Amiga gear is being made.

A bunch of pictures follow below.

The blue plastic on my milling machine is from the DVI connector.  Yes I sweated about it but remained clear of the wiring, I also clipped out some of the strain relief to help the cable clear the IDE ribbon.  The earth is still to be connected up on the flicker fixer, it can’t just float around in there with tape on it.  I was curious about whether I would have problems without it, no sign of any.

More Amiga

While I am posting about my e-waste collection check out this rarity.  Old Apple computers and Amigas had some similarities about them (same Motorola 68000 CPU for example).  Some bright sparks put Apple ROMs on a card that the Amiga could throw over too.  There is no changing between the two though without a restart.

I had the Amiga apart to replace a mouse port fuse (don’t ask) and took a picture of this esoterica.

I am told that, back in the day, one of these cards and a fully tricked out Amiga was faster than most (if not all) available Apples.  It’s just a curiosity to me though, I occasionally head over to Apple mode but I never have much liked using them.

VGA cable for an Amiga

Amiga’s horizontal and vertical sync signals are pretty rubbish.  This board holds some AND gates that serve to make it into a nice clean on/off signal.  A schmitt trigger as I understand it.  Too bad none of my monitors (yet) sync to 15.6khz…  Fun making it though.

Dot Matrix Printing

Lots of updates today.  This Commodore MPS1200 printer works well, the ribbon has been restored by emptying it out into a bag and spraying it with WD40.  I used a drilling machine to spool it back in and run it around a bit.  I read that water of any kind (including water in stamp pad ink) just causes corrosion.  The ribbon did not work at all at the start and the smearing shown in the video abated after a few pages 🙂  Commodore 64 fun.  Under the covers it is, I believe a Citizen 120D which is what I had when I was a kid.