Hopefully the last time I had to remove the back and all the modules for some minor fixes, the SE1X shows all its new wiring here.
The 4o wire ribbon cable has been tapped by the new controller board on top of the original boards. All switching signals and control voltages are handled here.
Shielded cable has been used to interface with the audio signals right on the analog board (which means removing some resistors and cutting some traces – ouch!)
All boards have been tested successfully now with this setup, two potentiometers turned out to be of wrong value for the possible parameter deviation and will be replaced soon.
But hey, what’s that?
(first of all, for the younger readers: this is a digital photo of an analogue scope screen, with a real cathode ray tube. Yes, I like those things when working with analog signals.)
The lower trace is the output of the RMOD gates (4070 CMOS device) with only VCO2 running, the upper is the triangle wave of VCO2 routed to the output.
First you might think this is a shot-through of the VCA controlling the RMOD amount to the master mix – nope, it is not.
It’s the hard switching of the 4070 causing a spike on the +10 volts rail, making its way into the analogue circuitry.
I’ll have to think about that later.