[sdiy] 8080-based synth reliability

[MTG]

If nothing else I'd love to see photos.  I'm guessing some wire-wrapped 
beast. Awesome!  I still have a 6809 breadboard system from the old 
days.  It's not doing anything though. :-(

On 10/6/2017 12:54 PM, Dave Brown wrote:
> 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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