Vintage Synth Repair

On Thursday 26 February 2009 03:24:46 pm heliumcell wrote:
> So are they basically acting like maybe what you would use a
> transistor switch for now? 

Yeah,  except that transistor switches have some leakage...

> Like you press the key down, it turns the neon bulb on, that then acts like
> a switch and lets signal through? 

Yup.

> Sorry if I am being obtuse. I probably need to see it in the circuit
> drawing to really get what is going on.

They probably have signal on one side of it and a common bus on the other.

> > They used those because designing keyers with early tech could be a
> > real bear, in terms of bleedthrough.  A neon bulb that's off is a *really*
> > high impedance,  by comparison with a lot of other circuits that they
> > could do cheaply and make a lot of.
> >
> > Old tube Lowrey organs also used a lot of those.

A good reference for this if you can find a copy is "Electronic Musical 
Instruments" by Richard H. Dorf.  Seems to be listed in google books but you 
can't see much of it there:

<http://books.google.com/books?id=oGmMqTsFidAC&q=electronic+musical+instruments&dq=electronic+musical+instruments&client=firefox-a&pgis=1>

This guy was president of the Schober Organ Company,  who used to sell organ 
kits.  He explains that and a number of other keyers in there,  as well as 
some of the design issues.  I *think* I found a copy in the library once...

-- 
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