Swell pedal effectiveness on Allen organs

[Guest]

I've recently started working with a 1981 Allen 300 MOS 2 organ.

Is there a way in which the dynamic range of the Swell pedal can be adjusted (i.e. widened)? At present, the pedal makes next to no difference in the level of sound. Also, it works intermittently, sometimes 'opening' and 'closing' without the benefit of a foot to guide it!

[myorgan]

I've recently started working with a 1981 Allen 300 MOS 2 organ.

Is there a way in which the dynamic range of the Swell pedal can be adjusted (i.e. widened)? At present, the pedal makes next to no difference in the level of sound. Also, it works intermittently, sometimes 'opening' and 'closing' without the benefit of a foot to guide it!

Giles,

Welcome to the Forum. I hope this is only the beginning of your participation in the Forum.

While I am not an organ technician, I do have an MOS-2 organ (505B). A Model 300 is probably an MOS-1 organ--unless it is a 305. I'm not sure, but I believe the expression is handled differently between the two generation organs.

From your description, and not knowing the exact model of the organ, it sounds to me like either an expression sensor is developing a flaw, or an electronic component is becoming intermittent. Also, have you made any changes to the organ lately? An example of this would be if you recently replaced an S-100 amplifier. An S-100 amplifier for an MOS-1 is not configured the same as an S-100 amplifier for an MOS-2. The expression circuit is handled differently.

While I anticipate the Allen techs to weigh in on your post, if you could provide as much detailed information as possible (especially recent changes) so they can more accurately respond to your post, that would be helpful.

Best of luck with your organ, and again, welcome to the Forum.

Michael

[Admin]

The Allen expression pedal is optical where the amount of light falling on a LDR (light dependent resistor) controls the level. The amount of light is determined by the position of a mechanical shutter controlled by the shoe.

When the shutter is open the level is at a minimum. When it is closed, the level is its maximum.

If the expression pedal lamp is burned out then, you'll get maximum level all the time. If the lamp is intermittent, the symptoms are as you describe.

[jbird604]

Check the lamp. It pries out easily from the side of the shoe with a slim screwdriver blade. You'll recognize it by the spiral-formed black wire going into a small round gadget in the side of the shoe assembly. It should be a small round bulb with a dot of paint right at the apex, the dot being there to keep the direct light of the filament from going straight to the expression cell. The lamp will not burn when it is out of the shoe, because the metal plate in which it is mounted is the ground return for the electric current. However you can touch the metal outer part of the socket to the metal surface to be sure the lamp is lighting up.

If it is not lighting, you need to replace it. The part number is "57X" but you may have trouble getting that exact lamp. You can surely find a plain #57 automotive dashboard lamp, then put a dot of permanent marker on the apex to help prevent that direct light effect.

There is also a slider resistor underneath the lamp area which adjusts the brightness of the lamp. Increasing or decreasing the brightness can affect the expression range and taper, so you might want to tinker with that. If unsure, just leave it where it is, but it won't hurt to play around with it. Make sure to re-tighten the little set screw when you are finished, as it might lose contact with the resistor coil if it isn't good and tight.

Another place to check is at the RCA jack where the expression is connected to the amplifiers, if yours has amps in the console. If the amps are not in the console, the circuitry is harder to find, so don't worry about it. But if the amps have expression inputs (often marked with an "X" on the cable), pull the plugs out, clean them off by rubbing on a little Vaseline and then wiping it away, then re-insert. This will insure that you have a solid electrical connection. This "Vaseline" routine is actually a smart thing to do with all the plugs and connectors in the organ, if you are inclined to do that.

[Guest]

Thanks for the hints. I didn't have a lot of time this weekend to 'search diligently' at the console, but I did find 'something' attached to the Swell pedal that had a wire attached. Anyway, I lightly cleaned it all off and made sure it all felt secure -- and hey presto, I have an effective Swell mechanism. Now I need to find time to take the back off the console and have a look at exactly what I was messing with.

Again thanks!

Giles

[jbird604]

That's good. There is probably a loose connection somewhere in the lamp circuit. Might have just needed to be pushed it tighter into the hole in the side of the shoe. But if you get time, take off the back and take a good luck at the whole thing. The small set screw on the slider of the resistor below the shoe assembly can be loose, thus making the operation of the lamp intermittent.

Good luck!

[myorgan]

Now I need to find time to take the back off the console and have a look at exactly what I was messing with.

Giles,

That's the story of an organist's life! Sometimes we do what we have to do to get through a service (without an emergency service call), and ask questions later. Thank you for being part of the Forum. I learned even more about the Swell pedal mechanism on my Allens from your thread.

Maybe I'm "all wet" on this, but I wonder if there was/is a current of air carried through your organ that might have dust particles in it. If so, that could have been the issue, from your description. In the building where I work we have positive and negative air flow for the heating/cooling systems, and I regularly find dust bunnies in certain restricted areas of the rooms where I work. One wouldn't think there are that many dust particles in the air in restricted spaces, but who knows? I'm glad you solved your own problem.

I hope you continue participating in the Forum. I've learned much from this thread so far.

Michael