Gyrophonic Projector Puzzle

[hossymandias]

Alright guys, I have a puzzle for you.

I recently acquired an unbelievably heavy Allen Organ Gyrophonic Projector rotating speaker. It looks and sounds crazy:

[img:640:480]http://img.canuckaudiomart.com/uploads/ ... intage.jpg[/img]

This is not a picture of mine, but mine looks exactly the same, WITH tweeters. In the back it has a DC motor that rotates the baffle, a chassis-housed power-supply, and a GREAT sounding tube amp.

I have rigged it up to play my guitar through it and I love it, but the problem is it only rotates at one speed.

The power supply is rigged with two relays that are supposed to deliver three different voltages to the dc motor, creating three different speeds. I can get the replays to switch, but the motor only runs when both are "on."

I'm assuming the circuit was designed to give one speed when relay 1 is "on," another speed when relay two is "on," and the fastest when they are both "on." Can anyone diagnose the problem?

I have replaced both capacitors, and I'm planning to replace the selenium recitfier diode and the selenium full-wave rectifier. Do you think this will solve the problem?

I can't figure it out.

I'll attach the schematic I've been looking at.

Thanks for your help!

[Regan]

Cool unit!!
Have you tried the speed adjustment pot?
I find the schematic a little confusing, could just be tired though
I think I would be tempted to gut all that and build a new dc control so it was fully adjustable, even programmable.
Regan

[Tillydog]

Cool!

I think you're right about the relays:

It looks to me like the field coil is permanently energised, with the armature supplied from the rectifier circuit which is supplied with various AC voltages through an autotransformer(!*). I doubt that changing the rectifier will affect anything, but you never know...

AC voltages to armature rectifier:

RL10 & RL11 both 'OFF' (as drawn) - motor is off

RL10 OFF RL11 ON - 16V

RL10 ON RL11 OFF - 27V

RL10 ON RL11 ON - 85V supplied via 15ohm 'Trem Adj.' rheostat (R88)

It appears that there are a number of voltage taps available, so it might be possible that different ones have been selected than shown on the schematic.


(!*) - In case you weren't aware, there is NO isolation from this transformer - everything in your circuit is directly connected to the mains - take care.

[hossymandias]

Thanks for the replies! Here are some pictures. I included some of the power supply innards, although I'm not sure you can see it well.

[hossymandias]

Regan, I have thought of gutting it and starting over too. Actually, my buddy who gave me this one has two more, and he really wants me to figure out how to do a variable speed control that could be housed in a foot pedal. Does anyone know if this would be possible?

Tillydog, I wasn't really holding out much hope for the rectifiers. I suppose it can't hurt to replace those selenium things anyway, I've read they are unreliable. But what would be the problem then? The relays? But the relays MUST be working, because I'm getting a speed when they are both engaged...!?

So confused.

At least it sounds awesome on that one speed, and if anything I can take out the tube amp and re-house it with the Jensens. Anyone know anything about early '60s Jensen Special Designs? Are they nice or commonplace?

[gui_tarzan]

I have that same unit out of an Allen organ I salvaged recently. It's definitely different and very complicated for what it does. The Hammond Leslie is a much simpler design. I've also heard those old Selenium rectifiers put out a poisonous gas when they go bad. Change it to a diode rectifier!

[hossymandias]

gui_tarzan, it certainly isn't very practical is it!? It weighs way too much to ever be worth using on stage. I'm planning on putting it on casters so I can roll it around the basement studio. Otherwise, it'll just be another flat surface to put tools, picks, and pedals.

[JazzGuitarGimp]

Yes, the smoke from a frying selenium rectifier is poisonous. Also, the voltage drop is equal to about 1V per fin, so choose silicon replacement carefully.

[Regan]

It wouldn't be that hard to switch it over with a modern dc controller- use a pulse width speed control on that motor- hell if you know anyone into microcontrollers like Arduino they could build you a killer setup, variable speed, programmable, stops at programmed spots, you name it.
Regan

[hossymandias]

Thanks Regan. I'm looking into the Arduino thing. I couldn't find any projects that deal with a 115v motor though. I also couldn't find any PW speed controls that deal with voltage that high, only 0-5v controls. Do you have any suggestions about where I'd pick one up if the Arduino thing doesn't work out?

Thanks again!

[gui_tarzan]

You could try a rheostat made for 120v applications, like a ceiling fan control. Just don't use a light bulb dimmer, it's not heavy duty enough.

[Regan]

Simplest option maybe a variable speed control for a wood router, not sure if it would work but its worth looking into. You can buy them ready made at Harbour Freight etc, or you can buy kits from lots of electronics outlets. If I was to redo it I would look into pulling that motor and power supply out and going with a lower voltage dc servo and controller. It would be much safer to work with and in the long run a lot more adaptable.
Regan

[hossymandias]

Regan, could I use this:http://www.amazon.com/gp/aw/d/B00CGXJSN ... 268&sr=8-2

Would I need a transistor to amplify the voltage?

I'll be honest, I am lost in this world of motors!

[Regan]

Thats the sort of controller I meant, 40v tops though. I think if I was going that route I would change the motor itself too. Motors are pretty cheap and that controller will handle up to 10A so you should be good to go with most medium size DC motors. You could try your motor at 40v though and see how it goes, it might have enough variation of speed to do the job fine, then all you would need is the controller and a power supply for the motor. Nice controller!
Regan

[hossymandias]

Cool. I am still confused about how the controller would work. Would I still need to supply the voltage to the field coil? Is this AC or DC? Then how to I run power through the controller?