I guess you already know how to play tape files through a computer soundcard into your Dragon?
For the missing PSU you can probably use a standard PC power supply, since it more or less delivers the voltages that the Dragon uses. I haven't tried this myself but I think other people on the forum have been doing this (Rolf?). Note that the Dragon 32 needs a -5V while the Dragon 64 needs a -12V. Old ATX supplies even had -5V but newer ones only have -12. It should be fairly simple to convert the -12 into -5 for the Dragon 32. Or inject the -12 into the Dragon internal PSU board, since it does conversion from ca -18V to -5 already.
Yep, I had to "improvise" a power supply a while back when my real PSU was lost (now recovered!). I ended up building a PSU from scratch rather than using a standard PC PSU. I can dig up the part list and create some schematics if there is an interest. The Dragon PSU is quite simple.
Yes, I think the (external) PSU is the same: It delivers AC 8.5V and AC 28V (with center tap). So if you find a one-to-one replacement for it there shouldn't be any issues. However, when connecting an alternative DC supply such as a PC ATX supply you will need to bypass the internal PSU (rectifier and regulator), which converts the AC 28V into +12V 0V -5V (Dragon 32) or into +12V 0V -12V (Dragon 64).
The Dragon PSU is basically a transformer providing 1 x 8,5 VAC and 2 x 14 VAC output. This is a fairly common transformer and easy to come by.
I buy my parts from ELFA. The parts from the ELFA catalogue are:
Toroid transformer 55 VA, 8,5 VAC + 2 x 14,4 VAC (part no 56-109-10)
9 way female D-Sub connector (part no 44-160-54)
9 way D-Sub plastic hood (part no 44-085-06)
The attached diagram shows the wiring from the transformer to the D-Sub. The transformer colour coding can be different for different transformers. D-Sub connectors always have tiny numbers next to the pins so there is little change of getting that part wrong.
