Vintage Synth Repair

On Thursday 26 February 2009 02:11:42 pm heliumcell wrote:
> Can anyone tell me what the electrical component that looks like a
> christmas light is in this picture? And what function it performs
> (generically obviously)?
>
> http://www.hallofgiants.com/images/misc/DSC_9087.jpg

Those are neon bulbs,  probably NE-2 or something fairly close to that.

> It is from a Conn console organ (a friend's). He says they glow orangey when
> a note is sounded, and I believe maybe there is one per key. 

Probably more like one per key per octave of note,  so for example if you had 
a 4' and an 8' stop selected you might see two bulbs glowing.

> I was guessing they were some sort of opto-resistor trigger type thing, but
> seeing them, I am not so sure I think that anymore, as they are not sealed
> or anything. I feel like I have seen these in something else too (a Farfisa
> maybe?). 

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.

> P.S. does anyone out there have access to Conn Organ schematics by
> chance (I can get the model number)?

I used to service organs,  but don't think I have much in the way of Conn 
schematics at this point.  What I do have left that I'm willing to part with 
is listed here:

http://mysite.verizon.net/rtellason/manuals.html


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