Thursday, July 13, 2017

Jitter Bug

Fix the jitter bug...!

Well, that's a relief! Last night I fitted a new transistor on G3 and the clock came back to life with a far more healthy looking waveform.

Tr1 Replacement on G3 - A bit wonky as I'm trying to be careful handling these boards to avoid breaking more wires.

 To be frank I'm still not totally happy with it though. I need to spend a bit more time measuring and checking because it still seems a bit, jittery... Not as bad as before but on the scope it's not as stable as the clock on G4.

I've Got The Bench Power

Before trying the transistor I thought I would have another go with a bench power-supply. But this time it was a linear supply, not the switch-mode one I borrowed. Ah, yes, this one is mine! I decided I needed a new toy for when I start work on the  MIDI interface so I bought cheapest one Farnell offered - a Tenma - and it's rather good for fifty notes. It'll appear in a later post no doubt.

Transistor Saviour

Initially I was a bit worried that I couldn't find a replacement for the 2AS509 transistor. I could find expensive ones or cheap ones in the states that would be expensive to ship over but nothing in the UK. Eventually I noticed that BC636 were close match and were cheaply available at Farnell. I bought a few just in case, as there we so cheap.

Back in the S.S.3.0

In any case, it works with the new part fitted and I plugged the output back into my mixer and had a listen - More noise! Oh, but this time I know what to look for. Sure enough a ground wire had snapped off G3. A quick fix and I was finally listening to the SS-30, as it should sound. Hurray!

To celebrate I decided to create a short video of me fiddling with the temporary front panel. Not the most exciting thing you'll watch today I would imagine but it's nice for me to have a record of these things.

You will notice that some of the pots are a bit noisy and sometimes when I switch things in it gets quieter, but overall things are working.

After a few more checks I should now be able to put everything back together in the rack case and after verifying it still works turn to the MIDI interface. The idea is to keep all the SS-30 boards inside the case, have the front-panel easily accessible and then just have the switch PCBs available to connect up with the interface. 

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