[sdiy] 8080-based synth reliability

[Dave Brown]

This is definitely DIY related and somewhat synth related in that it is a
digital 3 voice synthesizer.  In late 1976 I designed a dedicated 8080 based
three voice PWM synthesizer as a doorbell.  The code was based on a program
called Music for the Processor Technology Sol-20 computer.  I had to
disassemble the program to get it to run on a basic 8080 system using a
single 2708 EPROM and two 2114 static rams.  It used a simple transistor
driver for the speaker.  The 8080 is unmarked so I think it might even be an
engineering sample.

 

This system has continuously run for approximately 14,870 days or nearly
356,880 hours.  Well this week it died.  The processor is just absolutely
lifeless.  I had another 8080 from the same vintage but at least marked and
replacing it brought the system back to life.  Note that in the 40 years the
2708 has not forgotten even though the guaranteed retention is only 10
years.  I think it will outlive me.

 

It was a really progressive program for the time.  This doorbell also
includes a RS-232 interface so I could compile new music to upload to it for
special occasions.


Dave

 

David J. Brown

Modular Synthesis, LLC

 <http://modularsynthesis.com/> http://modularsynthesis.com

 

 

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