Vintage Synth Repair

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

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. 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?).

Just curious mostly.

-brendan

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

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


-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

So are they basically acting like maybe what you would use a
transistor switch for now? Like you press the key down, it turns the
neon bulb on, that then acts like a switch and lets signal through?

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

> 
> 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.

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...

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin