Category Archives: Hardware

HW

Minimig – Amiga clone, hand soldered

I decided to build a Minimig – a clone of Amiga, it can act as Amiga 500, 500+ or 600, with up to 4MB total RAM.

The interesting thing is that it uses an actual 68000 CPU – clocked at 7 or 50MHz in Turbo mode.

Other proprietary Commodore chips are implemented in FPGA.

I also built an ARM controller board – which replaces the small PIC micro, serves as SD card interface and feeds the FPGA with initial bitstream.

I’ve also included 3 hardware mod’s – additional 2MB RAM (sitting on top of original chips), SD high speed interface and lastly – joint stereo/separate stereo switch.

This was my first time soldering such a fine pitch (and expensive) chip – wasn’t all that hard.

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Saturn PCB Toolkit under WINE (MAC, Linux)

I was just watching an eevblog episode about VIA’s (research for my project), and I saw Dave using Saturn PCB Toolkit for various calculations.

Interestingly (and not surprisingly) the tool is only available for Windows, but I wanted it anyway, so I decided to give it a try under WINE.

It wouldn’t install, throwing a few errors, but then I did manage to install it on my Windows and copy the .exe file over to my mac,

and – voila, the thing works, it should also work on Linux…

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Cheers

Keithley 2000 bench multimeter repair, part 2

First part here

3 days later, my mouser order arrived to Japan (this is super fast), I got the relays, desoldered the bad one (proper desoldering tool is very useful here).

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(Right is new replaced, left is the old one for comparison, didn’t take it apart though).

Soldered the replacement and couple of screws later, I had the multimeter repaired, reassembled and ready to test.

(Don’t forget to note colors of the internal cables connected to the rear panel posts)

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First I realised that once or twice another test had failed (500.2), and also 600.1 and 601.2 (which was definitely a change from original 600.1,600.2,601.1).

When the test process asks for 4-wire short I literally used a 4-wire kelvin clips shorted, and this seems to be the reason why error 500.1 came up, and likely the 600.x ones now were because I shorted HI to LOW instead of AMPS.

Now, for 4-wire short I used pomona banana leads (I think 12-ich ones) to get as close to a “real” Keithley 4-wire short brace (it’s literally a brace with 4 banana plugs that snaps right into the posts).

After the change of leads – all of the tests succeed. Voila, I repaired the multimeter (but I think I will someday make a a 4-wire short brace for reliable testing).

Cheers