Amiga external 26 pin Gotek conversion

Rotek 26 pin external drive

I bought a cheap external housing with no drive to house a Gotek drive. External drives on E-Bay go for way too much and I didn't really want the drive itself so this seemed ideal. 

Rotek and Gotek

I obviously knew nothing and quickly found out why this is so cheap. The drive is too slim for a standard drive and the interface is a 26 pin whereas the Gotek is 34 pin. 

Not to be put off the next steps were to research the conversion.

Some searches online resulted in a couple of Shugart configurations, which was confusing.

Check the orientation of pin 1 from the 26 pin source as it should be +5V. 

Testing ground and 5V pin orientation

The following connections are required to hook up 26 to 34 pin. 

26-pin  34-pin         Signal             Description

cable    interface     Name            

2          8                /INDEX            Index

4          10              /DS0                 Drive Select 0

6          2                /DSKCHG        Disk Change

8          34              /RDY                Drive Ready/Disk Changed

10        16              /MTRON          Motor Enable

12        18              /DIR                 Direction

13        13               GND               Ground

14        20              /STEP               Step

15        15               GND               Ground

16        22              /WDATA          Write Data

17        17               GND               Ground

18        24              /WGATE         Write Gate/Floppy Write Enable

19        19               GND               Ground

20        26              /TRK0              Track 0

21        21               GND               Ground

22        28              /WPT               Write Protect

23        23               GND               Ground

24        30              /RDATA           Read Data

25        33               GND               Ground

26        32              /SIDE1             Head Select

I sourced the above from EAB (http://eab.abime.net/showthread.php?t=66905) and modified for the Gotek. Only 1 GND connection is really needed for Gotek as all ground pins are connected in the Gotek. The more you can connect the better for good grounding. 

All pins connected with jumper cable

A successful test of all connections left me with 2 choices. 

1. Solder all conversions on a prototype board. 

2. Botch a ribbon cable

Option 1 - Protoboard soldering

v3 board attempt

Super complex and after 3 attempts this eventually failed due to some random earthing of pins and the protoboard was sitting just a little bit too high to close the case.

There are alternatives that can be bought online. Even if these are wired correctly the challenge is to get these to fit into such a small case. 

This approach is a dead-end, on to option 2.

Option 2 - Ribbon cable modification

My decision to go with the protoboard was more to do with what I had at the time. Ordering some connectors and ribbon was happening after attempt one to create the protoboard.

Ribbon and connectors

This approach is much better as it fits into the tight space. Aligning the cables is a little tricky, but as long as the wires are pushed in gently they should stay when positioned into 34 pin header.

Final wiring of Gotek

This is much neater and works in the restricted space! 

Closing the case

With the wiring complete and screws attached the final change involves a bit of Dremel work on the Gotek itself. The front plate is a little tall and the led display requires a small amount of trimming, which doesn't impact the actual circuitry.

Final external Gotek

The case slightly sits forward from the case. This is due to the screw alignment between the Gotek and the external drive casing.

With the DF0/1 switcher this mod avoids installation of the Gotek inside the A500 case.