Rodgers C-505, range of dead keys in swell...

[AllenKitchen]

I guested on a casual worship service in a church with a C-505; these folks have a praise band and a rather nice grand piano from which most of their worship music comes. But they also still have a C-505 and use it weekly as well.

While getting used to the organ, I found that c'' thru e'' (five keys in a row), then f#'' on up to bflat'' (another five in a row) on the upper manual are completely unresponsive - except for that f'' right in the middle. No matter what registration, nothing sounded on those keys. The f'' sounds appropriately on all stops, as do all the other keys on that manual.

I poked around "under the hood" for a while (and, by the way, moved several burned-out tilt-tab lamps, swapping good ones in from the unused generals like MIDI, bass and melody couplers) - found the ribbon connectors from the manuals. Just for kicks, I swapped them - and found that the lower manual sounded all notes without error when plugged into the upper manual's connector. So I'm pretty confident that the issue is in the upper manual or its ribbon cable.

Time (and a desire not to bust something) kept me from tearing further into it. So I haven't looked at the keyboard guts in any depth. The fact that several keys in a row don't sound suggests that there is something wrong with a multiplexing circuit - but that one that DOES sound, right in the middle, is a puzzle.

Anyone care to share any insight as to how the keyboard sends work on that organ? Is it toast, or might I be able to jury-rig a fix?

Thanks for any responses..

..Allen

[arie v]

Allen,

I think so far your diagnosis is correct. If the Great keyboard works the Swell when you plug the connector into that slot on the I/O board, then the electronics are fine.

Looking at the schematics for the organ, they do not show the switching/matrix for the keyboards, so I would assume that it is just the switch and the diode on the keyboard. Matrixing if your description is correct, would be done in octaves. My guess is any one of the following,

1) bad connector on ribbon cable
2) connector poorly plugged in on the keyboard end
3) someone spilled something on the keyboard, and it found it's way onto the circuit board, corroding traces
4) connector on keyboard not soldered properly.

If someone did spill something on the keyboards, and I have seen this more than once, you may need to get a new keyboard circuit board, or better yet a new keyboard - if Rodgers still has them.

AV

[AllenKitchen]

Thanks very much! I'm going to make another speculation here, based on a very significant bit of info from you: "matrixing ... would be done in octaves." If that's the case, then there are TWO notes in that octave - the f'' and b'' - that are sounding; those are respectively at the tops of their half-octaves. That doesn't give me a whole lot to go on but it does suggest to me that there's something funky in the whole matrixing element for that particular octave as opposed to a) the individual keys or b) the ribbon connector.

Seems like the whole electronics cage has to come out before I can pull the keyboard. So I don't really know if it's going to be a very easy task then to test things once it's pulled apart.

But I'll "ping" this out to the forum - if anyone else reads this thread: anybody know of a C-505 that's otherwise problematic but which has a salvageable working keyboard? And, of course, any more feedback would be greatly appreciated.

Blessings..

..Allen

[arie v]

Hi,

According to the service manual, the cable from the keyboards to the Main I/O board is a flexible mylar cable (not ribbon cable), and at the keyboard end to disconnect (and then to connect) you have to release the lock by lifting the release mechanism the full height. This is basically called a locking zero force connector. These are easy to mess up, and once messed up, are garbage.

To disassemble keyboards from console
1) disconnect keyboard and piston cables from Main I/O board
2) remove 2 screws from bottom of key desk, which attach key desk to key cheeks
3) remove screws from back side of key cheeks (inside console)
4) slide keyboard assembly forward and out of console

Hope this helps

AV

[AllenKitchen]

Helps VERY much. That will save me at least an hour of trying to find this out on my own while not damaging anything!

While I was inside it last time, I found the piston cables and also found the mylar cables and their pseudo-ZIF sockets on the motherboard end. (Guess that's obvious, 'cause I talked about swapping manual cables.)

I will post an update if I obtain any more interesting info once I get the keyboard out - and again, I am deeply appreciative that you took the time to help.

Blessings..

..Allen