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First I sourced a replacement PSU, which handles at least 12Vdc/0.5A and 5Vdc/1A, from our local recycling site. I ended up buying a TRSF, model TR-05HHD, power supply which is able to deliver 12Vdc/1.5A and 5Vdc/2A.
Now this power supply sports a 6 pin mini DIN male connector and the 1541-II/1571-II/1581 are equipped with a 4 pin regular size DIN female connector. So this is an very easy job. Just replace the plug!
The output pin out is noted on the power supply so figuring out the pin configuration on the drive shouldn’t be a drag. Using i multimeter i figured that the internal cabling uses the industry standard.
Browsing famous FTP site Zimmers.net i found the following diagram:
- Yellow – 5Vdc -> pin 1 on the drive plug
- Black – ground -> pin 2 on the drive plug
- Red – 12Vdc -> pin 4 on the drive plug
Wanting massive storage and a minimum of soldering in your good old Commodore SX-64? I just found the solution by using the UIEC 3.2 without the daughterboard (article: UIEC-SD-BA) supplied by Jim Brain / Retro Innovations!
I made a little dual IEC connector to plug in between the internal drive and the controller board allowing you to add a secondaty internal IEC driver. The µIEC only emulates the IEC protocol so it’s not a real 1541 replacement and does not allow fast loader and most common trackloaders (which sends a binary to the drive’s memory and cpu) to function properly. If you need full 1541 emulation i would recommend the 1541 Ultimate 2 cartridge.
So this is what i have done to accomplish the additional drive space;
The only pin which needs to be soldered to the expansion board is pin 2 on the user port. This is the 5V feed for the protocol emulating uIEC card (see SX-64 schematic diagram)
Next thing is to make a dual IEC board. This was very simple, just a 6-pin female and two 6-pin male pin headers soldered to a little PCB.
Now when this is done just plug it in to the header P11 of the I/O board (see page 13 of the schematics) and connect the other wires accordingly. To figure out the pin assignment for the µIEC i used the following scheme:
P11 I/O ------------------- µIEC
pin 1 -------- SQR -------- pin 4
pin 2 -------- GND -------- pin 1
pin 3 -------- ATN -------- pin 7
pin 4 -------- CLK -------- pin 5
pin 5 -------- DATA ------- pin 6
pin 6 -------- RESET ------ pin 3
User port ----------------- µIEC
pin 2 -------- 5 volt ----- pin 2
If you like you can peek here for some hints.
Now the internal drive, number 8, and the SD card is accessible via drive 10 (default setting of the µIEC).
As this SX-64 already been modified (to sport a Teletron 1200 modem internally) the storage bay was already altered. I decided to use double-sided sticky-tape to mount the µIEC to the right upper side of the storage bay.
Everything worked out just fine even at first start up!