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Topics - FYG71

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Electronic Organs / Musicom organ system
« on: July 27, 2020, 02:34:28 PM »
I have a Norwich organ which dates from 1990 and uses the Musicom system.  The tone generation side of the organ has expired (not a problem as I want to use an external tone source) but the capture system remains intact and workable.  The organ is 2 manual and I would like to add a third manual with 8 stops (for which I have matching drawstops ready to go and compatible keyboards) My questions are:
1.  There appears to be space on the capture boards to accommodate the extra 8 stops, so should it be as simple as wiring them in?  The boards with Darlington transistors appear to have selector switches at the bottom to ‘channel’ the system.
2.  The Musicom system uses 8x8 matrix for scanning keys and pedals.  It is possible to add midi to the existing system easily or is it best to bypass with a stand-alone encoder?

Thanks in anticipation

Electronic Organs / Ahlborn H5 voice issue
« on: April 05, 2016, 05:54:28 PM »
I recently acquired an Ahlborn H5 one manual organ (1994 vintage) which has a curious fault.  Although a one manual organ, the stop voices are drawn from 3 chips and circuits from the digital processor board.  The stops from chip 1 all speak without issue.  Those from chip 2 all speak with harmonic distortion and those from chip 3 are barely inaudible.  I have completed a factory re-set but this hasn't cured the problem.  I also checked the on-board battery for leakage (a common problem apparently, which destroys the processor board) but this is intact. 

The distorted stops and those which are silent also behave in this way when heard through the external outputs and headphones and so I think the problem lies in the processor board rather than in the power amplifier side. 

Has anyone experienced this issue before who might be able to give some advice?  I have a copy of the schematic and some electronics experience in terms of replacing components.  It seems a shame to not try to fix this instrument as the rest is in good order.

I did have to replace the main capacitors on the power board as one had shorted out and also noted that the mains plug wiring had a very loose earth connection!  All fixed now.

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