dumb opto -ish kinda question using xmas lights

[Brymus]

If I had to guess, the bulbs in that organ are there as part of the oscillator circuits. Incandescent bulbs, with their varying current-dependent resistance, can be used to keep an oscillator circuit from over-gaining itself into distortion. See "The comprehensive phase shift oscillator thread" for some more discussion on this.

http://www.diystompboxes.com/smfforum/index.php?topic=106566.0

Two guys named Hewlett and Packard founded a somewhat successful company in their garage based on this fact!

And:

I have a few strings of Christmas tree lights in my basement because I've wondered just the same thing. I would guess that an incandescent lamp is yellow enough to match well to an LDR even without the colored filter but what do I know?

Darn thats what I was afraid of,well the guy didnt lie it does use lots of little light bulbs 
I payed less for the whole organ than what the 12" spkr inside is probably worth second hand so no loss at least.

[mac]

> When there is little current the resistance is higher

Resistance *rises* with temperature.

Oops! I was thinking low but wrote high... 
Thank you for noting my mistake.

mac

[PRR]

Xmas lamps for series-string may be 12V.

3V would be no-glow or you have to munch carrots then go in the coal-cellar at midnite to see the glow.

For longest life you would probably peak a "12V" lamp at 10V. It should be easy to get a 10V swing from a 12V supply with an amplifier to boost your small swing.

[GibsonGM]

Xmas lamps for series-string may be 12V.

3V would be no-glow or you have to much carrots then go in the coal-cellar at midnite to see the glow.

For longest life you would probably peak a "12V" lamp at 10V. It should be easy to get a 10V swing from a 12V supply with an amplifier to boost your small swing.

Yeah, that's what I'm finding, Paul.   After reviewing some Univibe info, I'm seeing that one needs a lamp driver to do this (well), which is what I suspected.   
So we return again to "will it make that much of an audible difference in exchange for the complexity/cost/effort?".    I'm thinking NO - technology advanced for a reason.
 
Might re-visit it just to give it an ear-test, but first I need to clear some of my 'experimental prototypes' away, either build or disassemble!!

[Brymus]

You just reminded me of something,not to hijack your thread,sorry
But I recently bought a old Baldwin organ for very cheap cause the guy said it used light bulbs not transistors for power.
I thought cool he must mean tubes...Anyway got it home took it apart and look what I found,are these actually light bulbs used as an electric component or are they small tube diodes?
There are quite a lot of them they are all paralleled to resitors from the way it looks.
Boy was I dissapointed even the power amp uses large Ge transistors,there are a ton of top hat Ge trannies(from General Electric LOL)
And a handful of what look like Si trannies,that have gold pins and look like flying saucers on 3 legs,they must have been top shelf items back then.
BTW the organ works fine in spite of some very old Mallory and Sprague electros.It even has a rotating horn style leslie tone cab on one side.

I am fairly certain after the replies given,the "light bulbs" in question are in fact this:

*High Positive Current Coeffiecient Resistors (HPCCR)*
Notice in the pic above the "bulbs" all parallel a single resistor.just like in the "Sonic Guard" schematic linked in the link below.

Scroll down to "How does Sonic Guard work?"
http://www.jblproservice.com/general_faq.htm

So I am thinking that these are in fact very useful little bulbs,just have to figure out what DIY application they could serve.

[Brymus]

Here is the explanation excerpted from the link above:

A pair of High Positive Current Coeffiecient Resistors (HPCCR) (LP1 and LP2) is connected in series with the high-frequency sections of the crossover network. These HPCCR (a specialized type of light-bulb) are wired in parallel with resistor R1 to form an attenuator. This attenuator matches the higher sensitivity of the high-frequency driver to the lower sensitivity of the low-frequency driver, thus balancing the high-frequency and the low -frequency output of the speaker system. As the input signal rises, more currect passes through LP1 and LP2. This causes the elements in these devices to increase in temperature. As their temperature rises, their resistance increases resulting in a reduction of the signal going into the high-frequency section of the network. When the overpowered condition creases, the elements will cool and normal system operation is restored.

[armdnrdy]

You might want to read through this:

http://www.pykett.org.uk/drkock.htm#ToneGens

It is very probable that these neon lamps are part of glow discharge (neon) oscillators used for voicing circuits.

[Brymus]

You might want to read through this:

http://www.pykett.org.uk/drkock.htm#ToneGens

It is very probable that these neon lamps are part of glow discharge (neon) oscillators used for voicing circuits.

Hmmm,still not sure,that shows the neon bulbs being operated at at tube plate voltages.
Also it states the neon oscillators were used in conjunction with tubes.
The organ I pictured uses 90% or better Ge transistors with a few Si versions as well,also the highest V shown is +/-35V in the Baldwin I have.
So I am not saying they aren't used for oscillators(are neon bulbs) but that I can't find any info in the Bio on Knock that clearly proves they are.
I will take another look inside and see what happens,I should have one of the kids play it while I look inside.
Still a mystery to me...

[armdnrdy]

I just pulled this off of an Organ forum:

http://www.organforum.com/forums/showthread.php?24868-Baldwin-orgasonic-72P-with-long-spring

reply #2

"Some old organs have divider circuits based on neon lamps."


I found this too. Scroll about half way down:

http://www.theatreorgans.com/walnuthill/player4.htm

[Brymus]

I just pulled this off of an Organ forum:

http://www.organforum.com/forums/showthread.php?24868-Baldwin-orgasonic-72P-with-long-spring

reply #2

"Some old organs have divider circuits based on neon lamps."


I found this too. Scroll about half way down:

http://www.theatreorgans.com/walnuthill/player4.htm

Well that answers two questions:
The bulbs are definitely neon,and the arrays are called PC packs.
Thanks for the links.

My 20$ Baldwin sounds real close to his Cohn 640,I wish mine had a power amp that was tube though.
I think the Leslie on mine sounds better,probably cause I hear it live.
But it's the same model a down facing 10" spkr into a two speed rotor.I really want to hack that for my guitar it sounds SO good.
Way better than any digital FX I have heard emulating a Leslie.