TR9090, bin it

Managed around some power up tests (no sound, MIDI seems to be recognized) for the TR9090 boards last week and noticed that my AC/AC transformer of choice was getting awfully warm. Voltage levels seemed ok though, so I figured it’s slightly underpowered (or too close the TR9090 spec). The part is new old stock (NOS) but doesn’t have any datasheet or markings (f.ex. to look it up in the net); I selected it just because it had a twin secondary and it outputted the required voltage (the TR9090 spec calls for at least 500mA @ 15VAC).

So, I figured I’ll save myself some time of testing through what I might have “in the shelve” and just order a new one which is safely overspecced on the amps. What I found got ordered on the following day and arrived yesterday. I sure was itching to resume testing and debugging to complete the unit! And boy oh boy, would I been happy had it been a simple replace-and-go kind of situation..

..but no. Despite what was indicated on the datasheet, apparently this new transformer didn’t like it’s twin secondary wired up centre-tapped. So after dropping in the new part and powering up,  I check the multimeter and it reads around 18 volts on the +5V bus. What t-h-e F-U-C-K just happened!?! Quickly powered down to double-check cabling/connections (everything fine) but at the same time realized that anything ‘TTL’ on the boards is definitely dead. Sure enough, quick check after wiring up the NOS transformer and indeed, even less alive than it was to start with.

..  $(#£!$$£ !

I could just feel my interest towards a TR-909 clone vaporizing into thin air..

Looks like this project is going on hold for a indefinite amount of time.