There was in newsgroups a message about rare opportunity to get a 3.5" floppy drive
to your precious Commodore 64. The author (Mika Leinonen) was selling factory
made PCBs for a 1581 clone, DCN-2692. The controller board was designed to use el cheapo PC HD floppy
drive. I took the easiest way and bought the board as all parts assembled and tested.
For the case hosting the drive and the board I got dead Cisco 750 Series ISDN Router.
Most of the parts are recycled from broken or unnecessary equipment. E.g. the floppy
drive was salvaged from an IBM AT-clone in Lahti Polytechnic's
garbage disposal.
At first glance the dimensions of Cisco 751 looked perfect. Its height was just over a standard 3.5" floppy disk drive and width allowed the Cisco-logo to remain its original position. It looked deep enough for easy fitting both drive and controller board. Oh, the horror when I found out that it was just over a centimetre too short. I took a tour on local computer shops for smaller drives, but I had no luck. Every drive was stretched to standard 15 cm depth, even if their mechanism/electronics were considerably shorter. So I had to do some violent acts.
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Unnecessary Materials Removed I took away the inner parts of the router and after taking measurements, I cut the mask with hacksaw and drilled the holes for mounting screws. Controller board studs at back are from malfunctioning A500 internal drive (at right) and combination of D-sub/motherboard leftovers. As an added bonus, the length of studs is easily adjusted by twisting. |
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Status Indicators My 5.25" floppy drive Turbo 9900 (an OC-118 clone) has bicolour LED as both power and active LED. I chose to carry out same method, because I did not want to drill any additional LED mounting holes and leave drive's original activity indicator unpopulated. My bicolour LED from Nokia BB512 baseband modem was common cathode(-) and DCN's LED circuitry has common anode(+) design, so this was out of question. I decided to use 2 separate LEDs. I tossed out drive's original 4 mm LED and instead put inside smaller 3 mm LEDs, which I soldered off from a PairGain Megabit modem. I soldered the green power LED onto the original LED's pads, although I bended its legs slightly to make room for the other LED. Because of the design, the DCN drives Drive Select -signal permanently low (active). Thus original active LED is continuously lit and of it came more or less perfect power LED. I hot glued the new active LED (red) next to the green one and wired it to DCN using wires from dead CPU fan. |
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Harsh Movements To get enough room for the controller board I had to remove protective metal plate from top of the floppy connector and bend the side plate. A part of the protector is utilized for controller board fastening. 7-pin connector is ripped from old NEC VCR. For some impractical reason (maybe a misthought) Vcc is not next to LED-pins in the DCN's header. The Device Select -pins are between them and this renders impossible to use PC's ready-made 3-pin power LED. This also makes difficult to connect those _DEVSELs to ground. You have to use one full length connector, which impedes flexible connection options. |
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Handcraft Cisco had a metal back panel, which was too tough for my old (t)rusty Swedish Mora-knife. Luckily I have supply of ZyXEL ADSL modems burned by a lightning surge. The plastic covers on these modems are almost in the same shade of grey that is used with Cisco branded products. I took one of the top covers and made a rough cut with sheet metal scissors. Then I spend few hours on carving and filing. The new plastic panel was thicker than the original and I had to carve a millimetre off from the edge to make a nice fit (seen in the next pic). This was the most expensive part of the casemod (about 2 euros). Because all my spare part modems had PCB version of DC jack and I did not discover any secure means of attaching them, eventually I had to go and buy the power connector(s). From the left are: 4-pin DIN for Commodore PSU compatibility, power switch from Nokia 160k BB modem, +5 VDC connector for the universal PSU of the Cisco 677 ADSL Router, holes for IEC Serial Bus connectors on DCN and a keyboard lock from my A1200T case as drive's device number selector. Floppy power connectors came from an ATX power supply which did not switch off correctly and the banduits are (unknowingly) sponsored by my employer. |
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Final Fitting Everything is connected and ready for a test drive. To ease pressure on floppy cable, I extended one of the vertical capacitors' legs and hot glued it to horizontal position (in the middle). |
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Protection Added The test drive was successful. But when I closed the top cover and tightened the screws, I got creeps. Instead of booting normally, it was blinking some error codes. For my surprise the plastic case was coated with semi-conductive EMC/EMI material and it was short-circuiting couple of pins around flash mem chip. I lowered the PCB by cutting off the corner resting over drive's head motor and also added a piece of plastic/aluminium foil laminate from that molested ZyXEL. I do not know if I fried something or is it by design, but now the DCN jams the IEC bus until a floppy is inserted into the drive. |
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Case Closed Cannot distinguish from the original ... |
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The New Face Looks surprisingly good, even if said by myself. Because the (mis)alignment of the power and active LEDs, the status indicator has nice pulsating gradient slide from green to orange when active LED is blinking. |