I opened up my EML 500 to see if I could find any clues as to the date that it was made. I've documented my exploration by adding pictures to the photo album of it on this site.
A look at the microphone potentiometer did yield a code (see picture) but when I plugged it into the search function of the site that Mike suggested, it didn't find anything. It seems that there are widely varying formats for this code, and this one didn't fit.
A look at the other electrical components proved to be more fruitful (see circuit board picture). Here's a list of the numbers that I found on the bigger parts: USA7417H, 7410, 7330, 7426H, 7413L. If these fit the format that Steve suggested of yyww, the earliest would have been made the 30th week of 1973 and the latest the 26th week of 1974.
Since the synth couldn't have been made before the latest component (7426) and the dates seem to be within a year of each other, I would estimate that this unit was finished in late 1974 or perhaps early 1975. Thank you Mike and Steve for your suggestions.
Rich
--- In emlsynth@yahoogroups.com, Mike DB <digiboy@...> wrote:
>
> By the way
> "Pots" refer to potentiometers, usually rotary controls with round
> knobs. On the 500 there is only that one "Mic Vol" that uses a
> rotary pot. You'd have to get inside the unit and look at the part
> that the rotary knob is attached to underneath, that's the pot. You
> would look for a number code.
>
> If you find the code, you could try here:
> http://www.guitardaterproject.org/potcodereader.aspx
>
>
> It could have been sitting around for a year or more before being
> installed, and it also could be a later replacement since they do
> tend to wear out. So it doesn't really tell you very much about when
> that particular 500 was made.
>