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.
Advancing the TR9090, I’ve been doing a bit of painting and decals for the enclosure this week. After pondering on decaling options (Lazertran or perhaps.. Lazertran?), I decided to test hand-painting them with a yellow paint pen instead. Turned out somewhat ok and it also gave the unit a kind of a funny/organic DIY look :)
The tip of the paint pen was too thick for finer details, so I worked on those with a regular sharp-tipped permanent marker. This left a slightly different tone against the black spray paint, but once I got the front plate spray-lacquered the difference evened out. This difference is still visible if you look up close and in some certain angles, but nothing that bothers me at least.
In case you were wondering about the milling on the back panel in my previous post, it was because the VCR casing didn’t allow for the output board to be used as-is. So, I simply cut it in half and bridged the halves with short cables. This allowed me to “sandwhich” them to the suitable opening on the enclosure.
All the connectors on the back plate needed additional mounting plates, I cut these from either acrylic or the PCB leftover bits. You can see half of the power switch mounting plate (made from a piece of PCB leftover) in the previous pic on the left.
Figured it was about time I resumed this project.. I was working on it some time during march but as it was just board parts assembly and toying around with one possible case that never got anywhere, I figured I’ll skip writing a post for it. The case belonged to a awesomely retroish defunct Akai cassette deck..:
.. Just plain brilliant stuff, so of course I spent a quite a time wondering how this could be turned into a neat housing for the TR9090 boards and a sequencer. I kinda started working on it too, but eventually figured that something rack-stackable might be more usable as it started looking like I’m not going to complete a sequencer for the unit any time soon (read: ever).
No actual progress on the drum synth itself, but instead I’ve been toying around with a sketch for a sequencer. As TR9090 is a plain sound module, adding a sequencer would make it more faithful to the original 909. More importantly, much more self-contained and ‘hands on’. Modifying something out of the MBHP platform would provide a relatively straightforward solution and maybe even I, the less programming oriented, could manage this. Heavy emphasis on the word ‘maybe’ ;) .. Here’s what I’ve been planning feature-wise: