Allen ADC-3100 playing wrong notes in top octave

[RobbieB767]

My recently acquired 27 year old Allen ADC-3100 just started playing wrong notes from the highest E on up. It's very bizzarre. It is not on all voices. At first I thought it was only a Swell division problem but it isn't, and it is only on certain voices. That combined with a Swell stop capture memory action problem and some distortion issues, I think I am bound to have to call an Allen technician to come to the house and get it fixed up. But I have a feeling that is going to cost a pretty penny. Very disheartening. And right before Christmas, of course.

[jbird604]

Robbie,

The wrong notes you are hearing in the top octave -- are they only on very high pitched stops such as 2' and mixtures? If so, what you've become aware of (since you only recently acquired the organ) is that the tone generator system in that series Allen has a definite limitation in the top octave. This applies not only to the smaller ADC models such as yours, but even to the big horizontal-cage and multi-cage ADC organs. The pitches of those note apparently exceed the capability of the system and what you get is a squeal that is nowhere near the correct pitch. Since this only affects the top few notes in the very highest pitched stops (which you would never play by themselves under any kind of normal circumstances) it is rarely noticed and not considered a problem by Allen. I don't know why they didn't just have those stops not play in the top octave, but I suppose that would have added some complexity to the keying system that they wanted to avoid.

Capture issues are often fixable by a careful and diligent user, since they may involve the reed switches on the drawknobs or the contact switches in the pistons themselves. These problems will yield to careful cleaning and adjusting of the parts involved. Of course, it's always possible for problems to develop on the capture memory board itself. Has the battery pack been replaced? If not, it could cause major problems in the future if the battery leaks and damages the board.

Distortion may be due to a faulty speaker but is more often a problem within the ADC amplifier. You can find out by switching the stops that are distorted into another amp channel or by swapping the speakers around. Problems in the ADC amp are often cured by dismantling the amp and cleaning everything inside.

So you may not have to spend a lot of money, but you may need to take time to learn how to fix a few items.

Best wishes and keep up the good work!

[RobbieB767]

Thanks for the reply, John. Regarding the wrong notes- it is only from the high E on up, and was not a problem before I went on vacation. I came home and this problem just occurred. It is not in the fractionals but in many voices including the Violas, Mixture, etc. etc. It wasn't there 2 weeks ago, I swear to you. The high E sounds like a whale fart, and the notes above that sound like some crazy modal scale. It's really freaky.
The capture memory problem is not the whole system, it is somewhat isolated. What happens is if you press the cancel or any of the swell or general pistons, EVERY stop on the swell bank pops out, as well as all of the alterable stops except one coupler, and a couple of tabs on the center panel as well. The Pedal and Great work just fine in that respect. I have received instructions to look for a battery pack possibly leaking or dead and I have yet to even find such a battery pack anywhere inside this thing. I have been shown pictures of what it would look like, and I don't see anything like that in there.
As far as distortion goes, there are some voices that seem only slightly distorted and some that I just don't use because they are grossly distorted.
Successful repairs we have made here at home so far include: replace tone card reader lights with LEDs (works great now) and volume pedals had burnt light bulbs inside rendering them useless (defaulting to full volume), changed the bulbs, and they work fine now.
I have some level of comfort with digging around in there but I don't want to get too in depth and make the situation worse by not knowing what I am doing. But that is where it stands right now. Any further advice is appreciated!

[jbird604]

Your problem with the capture sounds like you could have a defective Capture Supply unit or a problem with the DM3 board itself. I seem to recall that this is what happens when one of the plugs is completely pulled away from the DM3 board, so you might check those plugs to see that they are seated tightly. It's even possible, if someone has changed out the DM3 board at some time, that the plug was put onto the wrong card-edge connector. They are clearly numbered and labeled, so you can check to see if they are matched up properly.

The battery pack you're looking for was originally soldered directly to the DM3 capture memory board, which is a fairly large flat board that will be mounted directly on one of the plywood panels. We were warned many years ago by Allen to remove the batteries and put them in a box in the floor of the console. That may already have been done on your organ.

It is also possible that your organ has been updated with the new DM4 capture memory board which uses no batteries.

You should look around for batteries if you have an original DM3 board because they probably need to be changed.

Check your DM3 or DM4 board to see if one of the connectors is off or loose. It is good maintenance to pull them loose, blow away any dust or debris, then coat the card edge connectors with a very thin film of Vaseline before re-assembling them to the board. Just doing this might actually fix your problem.

Let us know how it goes.

[RobbieB767]

Thank you so much for the information. We will investigate that and get back to you with findings!

[RobbieB767]

It is DM4. No batteries. Clean/coat connectors has been accomplished with no change. The wrong notes problem is only with certain stops, not all. If it would be at all helpful, I could provide a list of good/bad ones. When using Violas II you hear both the right notes along with the wrong notes. It's only affecting high E on up. This is a much more upsetting problem to me than the capture memory, although I want both fixed. General distortion at normal volumes also bothers me. ViolasII IS very fuzzy sounding, and there are several voices I just don't use because they just sound like garbage.
Is it at all possible that insertion of some new tone cards I ordered from Allen might have caused a problem? Coincidental or not, it was when trying those new cards that the wrong notes problem surfaced.

[jbird604]

Robbie,

I can't think of any way that using tone cards could affect the organ. Just a coincidence I'm sure. The tone cards in the 3100 don't really even input voice data as they do in larger models, they just tell the internal synthesizer which voices to shift from the ROM to the RAM for a given playing session. When the organ is turned off, it all goes back to default.

There may be a loose wire somewhere in the capture system causing the stops to all turn on. It would take some diligent troubleshooting to find, but that is what may be required. Of course the DM4 board itself could be defective. You might try to find another Allen of the same vintage (anywhere from the mid-70's to the late 80's) equipped with a DM capture board, then you could try your DM4 in that organ and see if the malfunction goes with the board. It might even still be under warranty.

Your upper octave noises and your audio distortion may in fact both be caused by a problem in the ADC amplifier. We see this quite often in organs of that age. The distortion usually clears up after I completely disassemble the amp, remove the socketed power transistors and clean the legs before re-inserting, clean and lubricate the connectors on the amplifier pc boards, and lubricate the volume controls with WD-40. You could just do the easy part (lube volume pots) and also pull off the plugs and put them back on, and see if that clears it up.

You can post a list of the affected stops if you'd like and I'll see if they happen to all be in the same amp channel.

[RobbieB767]

We tried everything except swapping out the DM4 board because we don't have access to one. We also suspect defect with something else causing the wrong notes and distortion. I know my old Allen speakers are really crappy and may need to be replaced as well. Alterable 1 is not as loud as Alterable 2. Is that on purpose or malfunction? I wish we could fix these problems ourselves but don't see how we would get the boards needed to swap out, etc. I am wondering what the cost might be to get the local Allen tech to come in and get it back on track. An idea what it might cost? I think the keystop felts need to be changed also, we could probably do that if we knew what kind/where to get it and how to properly install it.

[jbird604]

Volume of the Alterable voices is adjusted (along bass, treble, midrange) on the boards in the cage. There should be a cage chart in the back of the console showing which controls affect which groups of stops, and which two sets adjust the alterables. You will need a very thin little screwdriver, not much bigger than a jeweler's screwdriver to adjust the miniature pots on these boards. Be sure not to put much pressure on them as they will bend away from you and might be damaged. I have never damaged one in 25 years of servicing them, but I have seen some damaged by other people.

[RobbieB767]

There is no chart in there anywhere. Nothing.

[RobbieB767]

Today a new problem has developed while the previously described wrong notes issue fixed itelf simultaneously. My mixture and most of the flutes, bassoon, etc. are all messed up now the full length of the keyboard. I think I have a major tone generator problem. I also think this organ is in fact haunted or has gremlins residing within it. Naught else it could be.

[toodles]

It's probably time to call an Allen technician. If you send me a PM, I can copy the voicing chart for you. I'm at work, and won't be able to scan and send until next Monday (the 17th).

Toodles.

[jbird604]

I think you have scratchy intermittent mini-pots on the TG boards. That particular problem with ADC Allens has been thoroughly discussed, so I think you can find some info on the forum if you look around. Briefly, the several tone generator boards have rows of controls marked "B-T-M-G" for each of the six channels (two great/pedal, two swell, two alterable). They are lined up along the edges of the boards and can be accessed through slots in the cage or cage cover. Use a very small slotted screwdriver and don't put excess pressure on the controls. Sweep each one back and forth a few times throughout its range, then return it to about where you found it. Once you have the voicing chart that Toodles has offered, you can see which sets control which voices, then you can tinker with the Bass, Treble, Midrange, and Gain for each channel until you get the balance you want.

- - - Updated - - -

You may also have some speaker issues. Allen speakers of that era have foam surrounds in the midranges, and if they are deteriorated, you can have distortion. The amps can also cause distortion, as I described above. The RCA plugs that go into the amps carry ordinary line-level signals, so you can connect them to some other kind of amp and see if the signal is clean. If the ADC amps are bad, you might be able to salvage them by disassembling and cleaning all the connectors and especially the volume control pots (WD-40 or other cleaner).

[RobbieB767]

Does anyone have information on how the 2 sets of 4 dip switches on the mixer board should be set for 2-channel vs 4-channel operation?

[toodles]

It depends upon the individual organ vintage--Allen changed the audio structure in early 1986, and that changed the boards they used.

Early versions had USRM-2 mixer. For 4-channel operation, all 4 DIP switch positions should be off; for 2-channel operation, DIP switch positions 1 and 3 should be on.

Later versions combined several boards onto one, and had an ADC mixer. This board had 2, 4-position DIP switches. SW1 worked as follows:
Position 1: ON=Grounds unused input on channel 2.
Position 2: OFF=combines channel 1 output with channel 2.
Position 3: ON=grounds unused input on channel 4.
Position 4: OFF=combines channel 3 output with channel 4.

SW2:
Position 1: OFF=combines channel 2 input with channel 1
Position 2: ON=grounds unused input on channel 1
Position 3: OFF=Combines channel 4 input with channel 3
Position 4: ON=Grounds unused input on channel 3.

For the ADC mixer, in addition there are 4 jumper positions. When installed:
LK1 is for Mono reverb
LK2 is for Stereo reverb
LK3 is for 1 expression shoe (the Swell)
LK4 is for 2 expression shoes (Swell and Great/Pedal)