Organ Building > Organ building and maintenance

Johannus Opus 230


Andrew Griffiths:
I have a Johannus Opus 230 with a fault. A Makin engineer looked at it for 250 but said it would be too expensive for him to spend any more time on it. Here's the problem: On the Swell the whole octave below middle C not sounding on any stops. When stop 34 (Celeste), 41 (Tierce) or 42 (Sesquialter) is put on there is a cipher at the pitch of G# below middle C. The blank octave transfers to the great when Swell to Great stop is used. Above and below the blank ocatave the Swell works correctly, as does the whole of the Great and the Pedal.
Could I get a circuit diagram, or could someone identify where the fault may be?

David Pinnegar:
From I see that it's an analogue instrument.

First thing to consider might be whether a mouse has run amok inside?

The service manual circuit diagrams are available from

It's a start to ascertain whether the manuals are a 61x1 set of connexions or a 8x8 matrix.

I wonder if possibly the people at Makins who knew about analogue instruments might possibly have retired?

The transfer to the Great is interesting. I've just given away to a friend a set of two Johannus manuals with another pair destined for him to make up a four manual portable beast. These have a separate set of contacts on the great duplicating the swell contacts - so the Great has both Great and Swell contacts and there will be a switch to toggle between one and the other. I'd think the most likely explanation for your troubles might be a rodent nesting under the manuals or somewhere in the wiring.

Best wishes

David P

 I think the Johannus you mention may used a TMS keying Ic to generate the different footages. there may be one per octave, so it could be the circuitry around the ic that might be faulty. [ or possibly the ic itself ].
the cipher may be a bit more complex to find, it is possible that some of the stops an non 16 / 8 / 4 / 2 footages may use a different keying ic [ but still use a TMS keying ic. ].
regards Peter B


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