Help with electronic diagnostic

[pedropol]

Hello and happy new year!

I'm trying to understand my Gulbransen Rialto K and solve "easy" problem first as I'm not an experimented electronic technician. Today problem is that C# does not play in the pedals. In fact, it plays with 8' stops but it doesn't with 16' stops. I haven't found similar problems with C# on the accompaniment or solo keyboards. This made me think that the C# generator card is not concerned, nevertheless I had a visual check just in case I see a component burnt. The problem occurs with both C# on the pedal keyboard with the same symptoms. I've cleaned the contacts for the pedals just in case of coincidence but the problem remains. According to Jan Girodot's technical book (see schematic below), I understand that C#1 can be played by a 16' or 8' stop. So I conclude it's not a mechanical problem.



How can I diagnose what's happening there?

Thanks
--
Pierre Métras

[VaPipeorgantuner]

If the bottom C# key plays the 8' pitches but not the 16' pitches, my first suspect would be the keying circuitry...check for a fault by comparing a key that does work (plays the 16' pitches)...trace the circuit path for the 16' pitch on a known good key. The Rialto K has 2 sets of generators, and if both sets produce a 16' pitch than the keying circuit is still a good possible culprit. does the same pitch play on the keyboard? if so, you can mostly eliminate generator as being bad. Check the solder joint on the affected key...a weak joint could also affect the note not playing.

Rick in VA

[pedropol]

My solution

Just for future knowledge, as my previous posts were deleted by the forum server crash, the problem disappeared after removing and replacing the cards in the rack. It could be oxydation on the contacts or their misalignment after moving the organ, the root cause is not really understood. But the lessons is that I'll have to check the electronic cards contacts whenever I get them out of the rack and replacing them.

Now I've created another problem as the C# channel keys are dimmer than the C channel ones, on all keyboards. Probably a similar card misalignment... But that's another story.
--
Pierre