Allen MOS help needed

[AMDguy]

I recently acquired an Allen MOS-1 organ, which I think is a 203c. I don't have any pictures at the moment, but I will try to get over to where it is stored to get some tomorrow. It has a few issues.

1. the capture/combination action is doing bizarre things. Allow me to elaborate; I brought the organ home and plugged it in for a quick run through, and the capture system worked wonderfully; the only anomaly I noted is that the cancel piston would indeed cancel everything, but it would always flip a tab on the great on, I think it was a 1 3/5' but I dont 100% remember. That was Friday. On Saturday, I was back where it was stored to get a little bit of a better lookover (I got it for free, so I just took it, worst case scenario I use it for a VPO project.), and to my surprise, the capture action system had totally stopped functioning. It is still doing the same thing. I have been leaving it unplugged (have to run an extension cord... leaving it plugged in tonight). I will plug it in, and turn it on; immediately upon turning the power switch to "on" it will flip a random assortment of stops in the pedal division; never the great or swell, only pedal. Once it gives this indication of life, everything relating to the capture system is totally dead. no response from anything. I have tried disconnecting the backup batteries, but that makes no difference. I have not yet measured the voltage coming from the power supply, I will do that tomorrow.

2. when playing a large registration (or anything loud), there are some static like noises coming from the speakers. I would assume this is because the speakers (integrated speakers..) surrounds are rotting and need to be replaced, as is common on many Allen speakers, but I suppose it could also be from a failing electrolytic capacitor somewhere. However, I am very inclined to doubt the latter, as when I am not playing anything (or playing something soft, only a few stops), it sounds fantastic.

aside from those two issues, it seems to be in decent working order, and as much as I love the sound from Hauptwerk, I am not at all inclined to rip apart a working organ... I can get used to the sound of an Allen :).

[Admin]

I'm unsure whether your model uses the early sequential capture system or the later DM, dual memory, system, but the first things to check are the capture back-up batteries. They need to be viable even when the organ is plugged-in and powered.

If a stop turns on when the cancel button is pressed there are several possibilities:

• Broken wire between the capture memory and the stop assembly
• Bad chip in the capture memory
• Shorted connector pins on the capture memory
• Bad transistor in the stop assembly.

[myorgan]

IIRC, the combination action on that organ only works if the organ is left plugged in. The backup batteries charge while the organ is off, but plugged in. Once you're working with a charged set of backup batteries, I suspect that will solve some of the problems you're experiencing.

On the MOS-1 and MOS-2 instruments, the discussion of distorted sound is mentioned in the owner's manual. If I also recall correctly, when you use too many stops the computer was unable to process that much information, and the result is a distorted sound. Using all the stops at the same time is also not good practice when registering the organ. At some point, adding more stops doesn't add much more to the sound.

Hope this helps.

Michael

[AMDguy]

Admin, I have the DM system, as I have the key slot (don't have the key) with the A and B memory positions. I will get over there at some point today to see if leaving it plugged in overnight helped with anything.

Michael, I left it plugged in overnight, I will get over there at some point today to see it that makes a difference. The computer not being able to process the information sounds like that might be it... I will also check this out later today.

[myorgan]

... I have the key slot (don't have the key) with the A and B memory positions.

I believe the key was the same for all DM capture actions. They can be cut at most hardware stores if you have an original. If there is a church in your area that has an organ of that vintage, perhaps you could borrow their DM key to copy. I have one you could use as well. I'm just over an hour away from you.

Michael

[AMDguy]

Ok, so I had a chance to go and play it for about 20 minutes, but I unfortunately didn't get any pictures. The capture action is still not working, despite sitting plugged in overnight, but I left it plugged in anyways.

when I turn the organ on, a random assortment of stops in the pedal division will turn on (same as before). Then the capture action is totally dead... almost. I played around with it for a while (the distortion is indeed because of too many stops) and got to like the sound. Then just for kicks, I started playing around with the pistons. Sometimes a piston (the set piston included, it does it too) will turn on a random assortment of stops across the whole organ. Then it is dead again. Give it a few minutes, and a random piston (with the exception of cancel), will do the same thing... rinse and repeat.

[myorgan]

See Admin's post below√√√√√

I'm glad you found a way to reduce the distortion.

Michael

[Admin]

Again, the first thing I'd check is the backup batteries. If they are bad, they won't charge even if the organ is left plugged-in overnight. Bad batteries have been known to cause random problems like you describe. Allen used different battery systems for the DM system over the years, but unless the DM board was replaced at some point, the batteries are likely to be in a cage on the floor of the organ for MOS-1 models. There is also a jumper that needs to be in place on the terminal strip connections of this unit. This jumper might have been removed if the organ was placed in storage.

In later models, the batteries were mounted on the DM board itself. If they have leaked, they've probably damaged the board and it may not be repairable.

My first thought was that a bad DM board was not a likely cause, but if pressing the Set piston causes stops to activate, that would point to a problem with board or the connections to it. (Look for connector pins touching each other.)

The only other assembly that is likely to be related to your problems is the Capture Power Supply. It provides 5 volts to the DM board and the high current pulses to the stop magnets. Bad power to the board can cause your problems and if there is something amiss in the power supply for the pulse power, it could explain the long recovery time after a piston is pressed.

[AMDguy]

It was definitely the batteries... I left it plugged in overnight again, and I just went over to find the capture system working perfectly, aside from every piston except for set turning on the alterable 3' on the great (even the cancel does this).

on a side note, is it possible to add pistons/toe studs to a MOS organ? I know that on the MOS organs, many of the features of the larger organs are there, just not being used. Does this include toe studs/pistons?

[Admin]

Check for broken wire on the alt 3 stop tab.

[AMDguy]

It has been totally crazy in the last week or so, but I finally got a chance to go and play it for 20 minutes or so... I am getting to like the sound more as I play it. I glanced at the serial number/data plate, and it is a MOS-1 123-C.

The capture system is back to doing what it was before...(it has been plugged in since I posted last). When you turn it on, a random assortment of pedal tabs will flip themselves on, and then nothing. I will get over there tomorrow with a multimeter to look into the power supply.

I have replacement batteries on the way and will be installing them soon...