Allen 123C Digital Computer organ help...horridly out of tune, thoughts?

[NYCFarmboy]

what would cause a Allen digital organ to be out of tune?

I have a Allen 123C digital organ I rarely use, plugged it and now its horridly out of tune....its odd...* *on specific notes spread out thru the keyboards, for instance low B plays the same (nearly) as tenor C, but other notes seem to play normally.

any thoughts on this?

[NYCFarmboy]

another clue:

the Gedeckt 8' flutes on both the swell and great are not out of tune at any time

along with the Octav 4'.* but the flute 4's are out of tune.

seems to be no ryhyme or reason..some stops are out of tune, others are not.

16' reed on the swell is in tune, but all 8' reeds (and 4' ) are out of tune.

also none of the pedal stops seem to be out of tune,

the transposer seems to be working just fine,

thoughts?

[jbird604]

Farmboy,

What you have just described is that the "Main" channel is malfunctioning, but the "Flute" channel is good. The fact that all pedal stops are OK confirms this, as all pedal stops are produced in the flute channel. Also, the 16' stops on the manuals are also generated in the flute channel even if they are reeds.

According to my Allen organ troubleshooting guide, out-of-tune notes can almost always be attributed to a MOS board failure. That is pretty bad news, as it will run you several hundred dollars to get an exchange board from Allen, and you'll have to go through one of their authorized dealers or technicians. A well-equipped and properly trained Allen technician will bring out his "kit" which will have a full set of the boards, and he or she will swap the boards one at a time until it's determined that the MOS board (or perhaps the KBA board or even the RM board, whichare also involved in the pitch function) is indeed the problem.

Another thing or two that a proper technician will check -- the power supply voltage, particularly the negative 27 volt output, should be checked and should be within a half volt of -27. The supply should also be tested to make sure there is no "AC on the DC" which would indicate a failed filter capacitor. The MOS board will misbehave badly if the -27 is way off spec, and also if there is AC on the DC. Either problem can be solved less expensively than replacing the MOS board.

One other possibility, and this is a best-case scenario -- I recently had a MOS-1 organ like that with one channel acting up and it turned out to be nothing but the card-edge connection where the MOS board plugs in. The connector was either dirty or a bit corroded. Cleaning it up and re-seating the board fixed the problem at a very small cost to the owner. Indeed, if the card-edge connectors and plugs on this organ have not been cleaned in the past few years that should be done as a matter of good maintenance.

So, do you do your own service? Or do you have a good, dependable, honest Allen tech nearby? If you don't know anyone, look at www.mitatechs.com and click the button to search by state or zip code.

BTW -- nice new pic.

Good luck.

John B

[NYCFarmboy]

thanks so much for that information!!!!!!