Allen Organ 632-D won't power up

[Thomas28]

I just recently got an Allen 632-D organ. I can't get it to power up by using the On/Off switch. When I plug it in, I hear the relay in the power module click. All of the unswitched outlets have power, but none of the switched have power. All the fuses, that I can locate, are good. Any idea what the problem could be?
Thanks,
Thomas

[John Vanderlee]

My first shot would be to check the contacts on the the relay you hear clicking. Sometimes they get burned and don't make. Unplug everything FIRST! of course.

John

[jbird604]

Aha! i see your thread now, Thomas! Glad you were able to get it posted here. Maybe now you'll get some good help. I'll try to offer some suggestions later today if I get a chance to consult the manual.

[jbird604]

Allen used a variety of methods for switching AC over the years. You probably have one in which the 27 volts is always on, and the power switch sends it to the relay inside the AC distribution box so it can turn on the rest of the receptacles. The relay could well be defective, and you can probably get a very nearly identical one from one of the many electronics distributors on the internet.

Before doing that, you should carefully trace all the wiring inside the AC distribution box to make sure it's not something else that is breaking the circuit, such as some kind of surge protection device. I once opened one up and found a big round orange thing which I assume was a "varistor" or something that had gone up in smoke and caused the organ not to power up.

If you want to, you can simply plug all the AC cords that are now in switched receptacles into an ordinary power strip and use the switch on the power strip to turn on the organ. Leave the cords that are in un-switched receptacles where they are and leave the main organ power cord plugged up, in case one of the cords goes to the memory battery charging unit. If your organ happens to have had the original DM or DM-2 board replaced with a DM-3 or DM-4, the charging unit does not need to be left on all the time, so you could safely transfer all the power cords to a new power strip and just abandon the AC distribution box.

[Thomas28]

Thank you both for your suggestions. John, I ended up taking your advice and took the easy way out and simply plugged all the AC cords into a power strip. It powered up!!! Yeah!!!! I intend to investigate it more and eventually repair it. My next task is to hook the speakers up to the amplifiers. My first attempt did not produce any sound. It is not as straight forward as when I hooked up my 600D. Are there any schematics available that show how to hook up the speakers to the amplifiers or does anyone know how to hook up the speakers?
Thanks,
Thomas

[jbird604]

If the amps are in an amp rack, you should have the four coax audio wires running from the console to the screw-on input of each amplifier. You should also have a brown power-signal cable with 2, 3, or 4 conductors in it that wires from a terminal in the floor of the console to a matching terminal strip on the amp rack. This cable carries the 12 volts to operate the relay on the amp rack that powers up the amps whenever the organ is turned on. And of course the amp rack itself must be plugged into a live 120 volt outlet.

The speakers can be connected directly to the two-place terminal strips on the amps themselves. In many racks there are a bank of relays to which the speakers may have been connected in the original installation, if there were antiphonal speakers. But it's perfectly ok, even preferable, to connect them straight to the amp terminals and leave the relays out of the circuit, as they can be problematic anyway.

There would've been four HC-12 speakers connected to the four primary amps, and probably a fifth speaker, normally an HC-20, which is an HC-12 with no mid or tweeter drivers, for the optional bass channel.

If you hook it all up and get no sound, you would need to go through the standard trouble-shooting process, which always begins with checking all the power supply voltages. I'd also have a close look to make sure everything is connected up correctly, as an organ of that age may have been tinkered with by someone trying to customize it or play it through a sound system or who knows what.

At least you have a two-computer system with two identical sets of boards, so if you can get just one of the systems working it will serve as a test bed so you can test the other set of boards.

MOS-1 organs are nearly bullet-proof, so you will probably find that once it's all hooked up properly and all the voltages are set correctly it will play. You may need to go through the basic maintenance procedure that we have described many times in various threads. In brief, every single point in that organ where electricity must pass across a removable connector of any kind, be it a card-edge that goes into a socket or a terminal strip that screws down, you need to take it loose, wipe on the thinnest possible film of Vaseline and then wipe it off cleanly before re-assembling the connection. All pots and switches should be "exercised" by turning or flipping back and forth a few times. Stop tab leaf switches need to be cleaned. Key contacts may need cleaning and/or adjusting.

That's a wonderful model with tremendous features and sound. I hope you're able to restore it to its full glory.

[Thomas28]

Hi John,
Thank you for the wealth of information that you have given to me!! There are 5 amps + another cabinet with the reverb and swell ped en chamade connections. I connected two speakers to the great amp and swell amp. I still did not get a sound. I tested the connection from the organ to the amp with a tone generator and the connection was solid (i.e. the tone from the generator came through the speaker). Also, I tested the voltage coming out of the 905-0058- I - the +5 is reading +10. I tried to adjust it but it won't adjust any lower than 9. The +27 is reading about 4 volts and the card reader voltage will only go up to 4. Again, all the fuses are good. Could this power supply be the problem? Would it cause no sound? The capture system works well and the amplifiers do have power that switches on when the organ has power and off when it does not. One thing more ...if the power supply is the problem, I have a chance to get a 905-0086 for a reasonable price. Would it work in place of the 905-0058?
Thanks,
Thomas

[jbird604]

ARE YOU SURE you were measuring all these voltages WITH REFERENCE TO SYSTEM GROUND? That is, you clipped the black probe of your volt meter to one of the several black ground wire terminals on the far right of the power supply fanning strip, then measured the -27, +5, and -5 by touching the red probe to their terminal? It occurs to me that you might be reading 10 volts on the 5 volt supplies if you are putting the red on +5 and the black on -5. That is not the measurement you are looking for, if that's what you are doing. And the -27 would read something crazy if the other probe is not on the system ground for that measurement too. So be sure you are measuring it right.

That power supply not working would certainly keep the organ from making any sound. That is the primary MOS supply, and the three crucial output voltages, which are -27, +5, and -5, must be present and must be very close to correct before the MOS system can work. So if it really is bad you need to get a new one or get that one fixed.

No other power supply will substitute exactly for it either. The 905-0086 isn't even close. It's a capture action supply, a completely different unit with different voltages coming out.

You must have the three main voltages plus the card reader voltage in order to operate that organ. And the voltages need to be arranged on the terminal strip in the same order so the fanning strip can be simply transferred to the new supply. So don't waste your money on buying something that won't work for you.

It is usually possible to repair those supplies. In fact, they are made up of rather ordinary parts. You might even find a local tech who could fix it for you. It is also possible to repair it by wiring in a set of standard modern-day "switching" power supply modules. This is of course not a job for a non-tech. But it is possible, and probably at a far lower cost than having Allen build you a new one.

Sometimes I see on ebay all the parts from a MOS organ being sold individually when someone guts a console to use for MIDI. You could keep your eyes and ears open for one to come along. There are some variations on that model power supply that would work in a pinch. So if you see one that has the same first seven numbers but a different "dash number" at the end, it might be close enough. You can post it here and I'll let you know.

Your best bet, barring the discovery of an identical supply, is probably to get a real Allen tech. That might even turn out to be a cheaper path than trying to figure out how to fix it yourself. The organ is certainly worth saving.

[Thomas28]

Hi John,
Again, thank you for your help. You were correct about how I was testing the voltage. When I went back and retested the +5, the way you said, it was reading +5. I reversed the wires, on the Volt-ohm meter, and tested the -5 - again it read correctly. When I tested the -27 it did not read correctly and turning the adjustment made no change. There is a television/electronic repair shop in town that I may check with to see 1) if they can repair it and 2) what it will cost. What does the sw ped en chamade ff stop do? Is it just for the trumpet stop or will it work on other reed stops on the swell?
Thanks,
Thomas

[jbird604]

That clears it up then. The -27 volt supply is the most vital of all, and is the power that actually runs the MOS chips on the big generator board. So without -27 there is nothing at all coming out of the system. Hopefully your TV tech can fix it, as it is a simple circuit. Probably has a failed diode or capacitor in the filter circuit on that supply. Worst case, he can get you a generic switching supply to wire into the unit to replace the old circuits.

I'm attaching a PDF of the schematic for his benefit.

The en chamade tab simply operated a relay on the amp rack that connected an extra speaker to the swell computer's main channel. This would give an instant volume boost to all the stops in that channel, which includes the trumpet and any card reader stops you might have loaded on the swell. So you could get a very effective Festival Trumpet.

In order for the en chamade to work, you would have to be sure the en chamade relay is connected and you would need to connect a very loud and highly efficient speaker to the output of that relay. Allen built a special speaker for this purpose called the HE-1 (later version is HE-2). But in some installations, an ordinary P.A. horn was used. Any kind of speaker that is exceptionally loud will work, as long as it can handle the power necessary.

[Thomas28]

John,
Last night I removed the power supply and today I will take it to the electronics store to see if they can repair it. Thank you so very much for including the schematics for the power supply and so generously sharing your vast knowledge. I will keep you posted.
Thomas

[Thomas28]

Update......I took the power supply to a local electronics shop and they repaired it. I was able to reconnect it, turned on the power and got sound. The next time I turned it on, a day later, I got static from the Great and Choir manuals. The Swell and pedal appear unaffected. I got out my volt-ohm meter and started checking voltages. When I checked the -27, right, unswitched, the static went away immediately. If I disconnect the volt-ohm meter the static comes back immediately. Does this mean that the power supply is still faulty?
Thomas

[jbird604]

Hmmm.... Well, does the -27 check at precisely -27? Are the screw terminals snug? Any loose wires or poor solder joints at the fanning strip?

I can't imagine that the very high impedance of the meter would have any measurable effect on the output of the power supply, so I tend to think it's more likely something mechanical at that connection point.

Also possible that the MOS board on the great/choir system is overly sensitive to voltage variations. You can try swapping the two MOS boards and see if the problem goes to the swell/pedal system.

A cheap fix would be to install a 10K resistor from the -27 terminal on the power supply to the ground, simulating the presence of the meter. I have no idea why this is happening, but that would be a quick and easy fix, if necessary.

[Admin]

What does the static sound like? Is it a crackling, cutting in and out sound or is it more like a high-pitched buzz, whine, or hash?

If it's more like the latter, I'm thinking that there is an oscillation on the power supply leads and it's the capacitance of the meter leads that cause it to stop when connected to the supply. As jbird604 points out, the resistance of the meter is miniscule compared to the rest of the load, but the capacitance of the leads could easily damp out some parasitic oscillation. Make sure all screw connections are tight, especially grounds.

[Thomas28]

I will recheck the connections at the power supply. The sound is crackling. Thanks.... I will keep you posted.