Allen 632 mos 1 great and choir not working suddenly!

[dw154515]

I have been on this form a bit in the last few months with an MOS-1 632 instrument that I acquired for our church.

http://www.organforum.com/forums/sho...is-Allen-organ

I've reinstalled, ran new RG59, new 14 gauge speaker wire to all speakers, installed HLabs units in it and got everything working and it has been GREAT for the last couple months!

I had just finished the postlude after the service and was ready to head home when suddenly the Great and Choir divisions quite producing sound. Obviously the great and choir manuals share the same computer in this organ so that means it's not an individual manual that's causing the problem, I'm assuming. The problem must be associated with the signal chain somewhere - Computer, DAC, HLabs units, etc.

Unfortunately, I had to bolt out of there and get back home to start teaching my students and didn't have time to do any diagnosing. One thing I can think of for sure to check (and hopefully this is the issue) is to check and see if the HLabs units are still powered on, and working. If the reverb unit and TWG are both powered on and functioning, what would be the next thing to look at?

I may end up just calling the "local" Allen repairman on this one.

Thank you all for the wonderful advice and help you've given to me along the way - it's been invaluable!

Best,

[jbird604]

Drew,

Troubleshooting always begins with power supplies, and since the 632 has two completely separate MOS systems within the console, there are separate power supplies for each system. Check with a meter to see that both supplies are putting out the required voltages -- plus and minus 5, minus 27, and the unregulated +12 (which can be up to 14 or 15 volts in some organs). If a voltage is missing, check the associated fuse. If it's not the fuse, you will probably need a service call.

If power supplies are OK, the next step is to test audio. You can pull the RCA plugs out of the jacks at the DAC boards, touch the tips, and get a hum from the associated speaker. If you don't, the trouble is downstream from there. Could be the amplifier mutes, since each mute relay serves the two channels of each MOS system. You can unplug the mutes from the amplifiers to test this theory, but be aware that there will be a loud turn-on and turn-off pop with the mutes removed.

If audio is OK, I'd next check the DAC board by swapping the DACs between the two MOS systems. If the Gt/Ch now plays and the Sw/Ped is dead, you've found the bad board. If the DAC is OK, I'd go on to swap the MOS boards themselves. Be very careful with the MOS board as it is quite susceptible to static discharge damage. Just be sure to ground yourself to a large metal object or the organ ground before touching the MOS board. (Always be sure the organ is switched off before removing or inserting any board!)

If the MOS is OK, you could swap other boards, such as the clock board, between the two systems. Since you have two of every board in the organ, you should be able to find the problem by swapping boards around. Once you know which part is bad, you'll have to begin the search for a replacement, or else pay your local tech to send it off to Allen for exchange.

Good luck!

[jbird604]

BTW, I see on your website that you are from Pine Bluff. I think we've met sometime. My name is John Birdsong and I used to do a lot of piano tuning and other instrument maintenance in Pine Bluff. I believe I either tuned your piano or at a church where you played. Your name sounded familiar when I saw your signature and then I looked at your site. Glad to see that you've taken your music so far!

[dw154515]

Hey Mr. Birdsong!

Yes, you tuned 2 or 3 pianos for me! An old Kimball (?) in my old church, my old upright and I believe my grandmothers Kohler & Campbell spinnet.

I've since moved to Indianapolis to attend Butler University and am wrapping up my M.M. in Composition. I took up residence here and am now the organist at a local Lutheran church. What a small world!

I found this Allen on Craigslist for $800! The move across town was quite an undertaking but well worth it. The upgrade from the old toaster was GREAT! I also couldn't just let it hit the scrap pile. I live on the southside of Indy, so I'm only able to get up to the church (downtown) once a week for service. It will be Sunday morning before I can get up there again - so I was fishing for suggestions before time came.

Thank you for all the help, I greatly appreciate it. I will keep you posted.