CPC 6128 3" drive as external drive

[Liartes]

Hello,


I put a Gotek in my CPC 6128 as it is my main way of loading games on this computer, but I would like to keep the possibility to read 3" floppy disks.


packaging the floppy drive in a 3D printed case with a dedicated PSU would be perfect, but I didn't find any fitting cable for this project nor guides to build one.
Is it possible to use the old internal drive as an external one without the FD-1 hardware ?

[Bryce]

On a 6128 you only need the drive and a suitable powersupply (5V and 12V) to use it as a second drive. But that's all that is in the FD-1 anyway. There's no additional magic happening in there.

Bryce.

[Liartes]

Thank you Bryce for the confirmation. I will try to map 34 pins connector (EDGE) to 26 pins using this ressource page : https://www.cpcwiki.eu/index.php/DIY:Floppy_Drives#CPC-CD201_.28internal_floppy_26pin_connector.29

[Liartes]

Combining these 2 wiki pages http://www.cpcwiki.eu/index.php/Connector:2nd_disc_drive_(CPC664,_CPC6128,_CPC6128%2B) and https://www.cpcwiki.eu/index.php?title=DIY:Floppy_Drives&mobileaction=toggle_view_desktop

I get a nice corresponding pinout from the range
(26 pins) 26 to 9 -> 1 to 18 (34 pins)
And the pin 2 that goes to 27
There is 2 more pins to map from the 26 pins side, and 2*2 destinations possible as the drive would be A or B.

Do you think I could crimps 2 edge connectors, allowing usage as A or B ?

The cable would be something like :

Floppy drive side (26 pins)
**********************
First edge connector (drive as B)
(26 pins) 26 to 9 -> 1 to 18 (34 pins)
(26 pins) 8 to 4 -> 19 to 23 (34 pins) for motor enable 1 and drive select 1
(26 pins) 2 -> 27 (34 pins)
**********************
Second edge connector (drive as A)
(26 pins) 26 to 9 -> 1 to 18 (34 pins)
(26 pins) 8 to 4 -> 21 to 25 (34 pins) for motor enable 0 and drive select 0
(26 pins) 2 -> 27 (34 pins)

[vasilisk]

Check here
https://www.cpcwiki.eu/forum/technical-support/connecting-an-internal-3'-drive-as-external-b/

[Liartes]

Thank you Vasilisk, I missed this topic while doing my research !


As I understand your conversation, this is possible to use a non-modified drive as A or B by twisting some wires. after much reading I still does not understand why "select drive 0" as no role in this, but I won't question too much on an already tested and working solution.
I turned it into a table with common 26 pins side, and 2 differents pinout for the 34 pins side, if someone want to make a unique cable with 2 edge connectors.

[Liartes]

Here it is, the ultimate cable 3" B drive ! 


First edge connector is for modified 3" drive as described by Audronic on the other topic.
Second edge connector is for stock 3" drive.


I misinterpreted Audronic explanations and photos and despite the result work as expected, it was not what I wanted to do : a cable with a connector for drive select 0 (A), and another connector for drive select 1 (B).

I tried swapping some more cables to connect /DRV1 and /MED1 to /drive select 0 and /motor enable drive 0. Unfortunately nothing happened and the drive does not react to CAT. I figured out the wiki informations I based my table on was wrong : in the cpc 6128 service manual, there is no /MED0 and /MED1, only a MOTOR ON.
The correct wiring (in theory) is in attachment, with pinout based on the service manual.


I built another cable, and this one does not work at all. As stated in the wiki, /drive select 0 seems not connected on the edge connector. I have a question then : how do 3,5" disk drive cable with a short between pin 11 and 12 for primary/secondary disk position operate the switch ?


Edit: remove missleading cable mapping

[Liartes]

Yeah ! Finally it is working !


The solution is the same as the 3,5" disk drive short on pin 11 & 12.
With the wiring attached, shorting 4 & 5 set the external drive to A. Removing this short set the drive to B.

[Liartes]

To follow up with the cable, here is a casing to protect the 3" disk drive : https://www.thingiverse.com/thing:4607020.
I am thinking about drawing a model with an internal PSU and power barel to plug a CPC 6128 12V, some sort of mini FD clone allowing you to power up 2 3" disk drive at the same time. I don't really see an usage for this, but would be a nice DIY alternative to the FD-01 which are quite expensive nowadays.