The Story of Amiga A600 Lang aka Wide Edition (2007-)

The keyboard cable of my A600 was reaching the end of its life span after too many removals. I also have a half-dead A500 with working keyboard, so I started thinking about replacing the A500 mobo with A600 mobo and ultimately creating some kind of A500+ Deluxe having ECS/2MB/HDD/KS3.1. After some twists'n'turns I noticed that the A600 have quite similar back connector layout as the A1200 has and a left-over A1200 case from the tower project might be more suitable. It turns out that the connector layouts are exactly the same and the A600 mobo slides in almost perfectly. Only small removals of some plastic is needed.

Disclaimer
All information on these pages is provided "as is". The information may be misleading, inaccurate or completely incorrect. I take no responsibility if you break, fry (as I did) or in other ways demolish your assets after following these instructions. These pages contain graphic images of violence towards valued Amiga hardware. Viewer discretion is advised.

Keyboard

For the A500 keyboard you need to tap in KB_CLK, KB_DATA, KB_RES lines and also feed some +5V. Some keyboard hackers say that keyboard works even if the original keyboard MPU was left online, but I decided to leave only reset connected to allow booting without a keyboard connected. In general you cannot connect two logic outputs from MPUs (excl. OC) in parallel without increasing the risk of the Magic Smoke leaving the chips.

Instead of bending the legs of the keyboard MPU (U13), I decided to cut the traces coming from pins 41 (CLK) and 42 (DATA). Visible traces are easier to restore than broken solder pads under PLCC chip.



The A500 keyboard has 8 pin header connector and it needs some kind of adapter if you want to detach the keyboard without a soldering iron. Luckily my old NEC VCR came to rescue (again) and supplied a suitable connector. I soldered it onto small piece of a stripboard and added a protection diode for the reset. Then I was ready to connect the necessary wires. You can find suitable SMD resistors on the bottom side. For the power I used the joystick port pins 7 and 8.

Note from future self: Pin 7 has 4R7 current limiting resistor, do not use!



The keyboard signals can be found on resistors:
R511A   KB_CLK (yellow)
R511B   KB_DATA (white)
R511D   KB_RES (green)

A500 keyboard connector pinout:
1 CLK
2 DATA
3 RES
4 +5V
5 (NC)
6 GND
7 PWR LED
8 FDD LED

About reset:
The reset output of the A600 MPU is delayed using generic 555 timer (U14). Because the _KB_RES signal is active-low and 555's uses active-high logic, the signal needs to be inverted (logical NOT) before allowing it travel thru the motherboard. On A600 the 555 drives a transistor with pull-up resistor on its collector. This is known as Open Collector (OC) output. One of its advantages is that you can combine multiple outputs without any additional logic glue. OC output has high impedance when it is in logical 1 (pull-up handles state) and short circuit (to ground) in logical 0, so there is never a situation where one or more outputs are actively supplying voltage and other short circuiting it to ground. Instead on A500 keyboard the 555 drives 3-input NOR (74LS27) wired as NOT, so there is a (small) chance of burning chips when A600's 555 is driving the reset signal low and 7427 is keeping it high. You can protect the 7427's output in that case by adding a reverse-biased diode (cathode is connected to the 7427's output). Because the diode increases the low level voltage about 0.6V, the logical low is now near TTL standard's max 0.8V and this might not work properly. In that case you need to use a real AND-gate.

Case Tuning

The connector layout is identical on both A600 and A1200 excluding joystick/mouse ports. That was nice because this way holes and texts on back plate are correct. My only problem was how I am going to attach the joystick port extensions cables. I was thinking about making holes into the right side like in original A600 concept or maybe re-use somehow the backside holes of A1200 case. Then I remembered that I still have the A1200's bottom shielding which already has suitable holes.



The PCMCIA connector on A600 mobo was few millimeters off, so I had to saw some extra space.



The red circles mark spots where I made modifications. Basically I drilled few holes, added mounting studs and removed some pieces of plastic.



The heart of my Amiga is progressing nicely. The joystick and keyboard connectors are ready.



Looks like a factory made. There is also a less professional looking mouse/joystick selector for the port 0.

LEDs

Making the LED mod was maybe the biggest job to do. The A500 keyboard has only power and FDD LEDs and A600/1200 have separate triple LED PCB, so I had to somehow join these together. The A1200 has integrated keyboard MPU on the motherboard and there is no extra daughterboard on keyboard assembly. Thus there is plenty of room for the LED board. The LED board is quite thick and it is not going to fit between the case and A500 MPU board. I removed the riser studs under the LEDs to gain some space.



I also removed some supporting plastic from the case and shortened the mounting studs. Now the LEDs slightly popup from the surface, but it is no big deal. Actually the LEDs are now more distinct, because there are less light leaking from the nearing LED. A rewired floppy power cable from a dead PSU got a new meaning for its existence.



I removed original LEDs completely and repositioned C7 and C9 to the bottom side of the board.

MemClock-thingy (2013)

I ditched the old memory only expansion for state of the art A604 expansion from Jens. A604 has some mem, but also battery-backed up realtime clock, two A1200 compatible clock ports and a port for Indivision ECS flickerfixer.

PCMCIA activity LED activation (2017)

Every company tries to save pennies everywhere they can, Commodore being famous about that practise. One of the targets were at 1990s most likely unnecessary PCMCIA activity LED, known as _CC_ENA. On the A600 the CC activity is shared with floppy activity LED. Pads and traces are already present on the PCB, so you only need to add one 4.7k resistor (R638) and PNP transistor (Q634). The 10k pull-up resistor (R637) was already there. Original SMD transistors are 2N3906, I used BC857.



Thanks DoobreyNet for the hint. Please note that probably collector C and emitter E are swapped in the picture on the site. On my A600, the collector was pointing to the front of the MB, not the emitter.

'capped Vampire's Bite (2018)

After about year and a half in the waiting list, it was time to get some immortal bite under the hood. While waiting the Santa with early Xmas present, I decided it was finally a time to disassemle the Beast and put in good use the previously acquired re-capping kit. Not having proper SMD soldering equipment - nor the talent - the result was few broken pads, but anyhow, the patient survived from the operation.



The DVD-ROM in previous setup was hovering over the CPU, so it needed to be shifted right quite much. Luckily it fitted nice between Vamp's HDMI output and joystick ports. Currently the HDMI cable is straight 50cm slim v1.4. I may someday order a 25cm (10 inch) left-right angled cable, which should be perfect fit and not pressing against the optical drive.



Nice HDMI 1.4 compatible output, could be little overkill for 720p. The adapter was muy cheapo 0.89€ incl. P&P purchase from Ebay.

The North remembers longer (2020)

The keyboard connector got new wires. I also re-ordered wires from keyboard PCB to have some meaningfull colors. Red and black for power, blue for reset and matching colors for (unused) case leds.

The A604 RTC got CR2032 coin cell holder with better accessibility via trapdoor. The original CR1220 is much more rare (here at north) and have atleast 5x less capacity, whereas CR2032 coin cells can be found in every tiny neigbourhood store. The timekeeping should be running through the years of utter abandonment and loneliness.

Jump to
Part 2: ATA connections
Part 3: Power supply