Synth-DIY Yahoo! Groups Archives

Thread

Re: [vintagesynthrepair] Digest Number 217

2002-05-09 by ed hallborg

I don't know which kind of bulb goes in there, but what is that for anyway?  I just rescued an old "Melo-Sonic" mini organ from the trash  and it has that glowing light from the expression pedal unit as well - never opened it up to take a look though.  I'm sure there's some rational purpose for it - but what?
Ed


Message: 5
Date: Thu, 09 May 2002 05:08:14 -0000

Show quoted textHide quoted text

From: "gcmci" 
Subject: hammond organ expression pedal

Does anyone know what kind of light bulb goes in a Hammond expression 
pedal?

Gary Chang

________________________________________________________________________
________________________________________________________________________

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ 

---------------------------------
Do You Yahoo!?
Yahoo! Shopping - Mother's Day is May 12th!

Re: [vintagesynthrepair] Digest Number 217

2002-05-09 by ed hallborg

Thanks Lynn (and Peter B.) for the tips towards Allen organs, I will have to contact them, I would have never guessed they would still provide any support for the RMI line.

-Ed


________________________________________________________________________
________________________________________________________________________

Message: 4
Date: Tue, 7 May 2002 00:20:49 -0500

Show quoted textHide quoted text

From: guitarampsky@...
Subject: Re: Digest Number 215

Ed,
Have you tried Allen Organ Co.? Rocky Mount Instruments was a division of
Allen. I have gotten RMI piano parts and service info from them in the
past.
I haven't posted on this list before, so my name is Lynn and I work for a
company that provides tech support for USA built Baldwin organs. If I can
be of help to anyone, please ask. The only 'Vintage synths' I have are a
CDX-652 and a Chroma Polaris, I'll never admit to owning an M1. I'm
hoping to some day find a Baldwin 'Porta Synth a Sound', just for
historical reasons ( or should I say hysterical!), also a Baldwin BC-1
&/or BC-2 combo organs.
Have a great day,
Lynn
<><

> Message: 1
> Date: Sat, 4 May 2002 08:20:54 -0700 (PDT)
> From: ed hallborg 
> Subject: Re: Digest Number 214
> 
> 
> Hi all,
> Does anyone know where to find any info on an RMI DK-20? I guess it 
> was the sucessor to the electra piano line. I picked it up a while 
> back, seems to work fine but I can't figure out how the synthesizer 
> waves and modifiers buttons are supposed to work.
> Anyone worked with one of these before?
> Thanks,
> Ed
> 
> 
> 
> ---------------------------------
> Do You Yahoo!?
> Yahoo! Health - your guide to health and wellness
> 
> [This message contained attachments]
> 
> 
> 
>
________________________________________________________________________
>
________________________________________________________________________
> 
> 
> 
> Your use of Yahoo! Groups is subject to 
> http://docs.yahoo.com/info/terms/ 
> 
> 
> 

________________________________________________________________________
________________________________________________________________________

Message: 5
Date: Thu, 09 May 2002 05:08:14 -0000
From: "gcmci" 
Subject: hammond organ expression pedal

Does anyone know what kind of light bulb goes in a Hammond expression 
pedal?

Gary Chang

________________________________________________________________________
________________________________________________________________________

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ 

---------------------------------
Do You Yahoo!?
Yahoo! Shopping - Mother's Day is May 12th!

Lightbulbs in old volume pedals

2002-05-10 by Eirikur Hallgrimsson

The lightbulb shines onto a photocell which changes its resistance
according to how much light falls on it.  I think it is in the direction of
more light reducing the resistance.   It's a semiconductor device with the 
light taking the place of the base junction in a transistor.

This has two significant advantages for a volume pedal.  It can't get 
scratchy, like a dirty potentiometer, and it doesn't require any gearing 
or mechanism that would break down over time.  It's probably cheaper, too.

So, the pedal just moves a little shutter that shades the photocell.   On 
one unit I worked on, the shutter was actually a piece of plastic with a 
V-shaped slot in it.  The pedal moved this past the photocell, allowing 
most of the area to be hit by the light at the wide end of the V, and then 
reducing the exposed area very nicely and slowly.   

It's an elegant piece of design, and apparently very reliable.   Putting 
any kind of unsealed pot in a pedal is just asking for dirt to get in.

Obviously light-bulb life is the major limiting factor.

I think that just about any bulb of the right size and voltage would 
probably work, perhaps throwing off the calibration a bit if it were 
significantly brighter or dimmer.   I also expect that the bulb is being 
run on a lower than rated voltage, to get longer life.

If you can't read the legend on the bulb, I would try measuring the 
voltage that is fed to it.   I'd try a bulb that is rated a bit above 
that, maybe half again.   The voltage may read read, high, though, because 
the bulb would normally load it down.   You may have to experiment with a 
couple of bulbs.   They shouldn't be at all expensive.

Eirikur

Vintage Synth Repair

Re: [vintagesynthrepair] Digest Number 217

Re: [vintagesynthrepair] Digest Number 217

Re: [vintagesynthrepair] Digest Number 217

Lightbulbs in old volume pedals

Move to quarantaine