Troubleshooting a Themodist
By Craig Brougher
David Blake was wondering how he could troubleshoot his Triumphodist Brinsmead Themodist. Said it seems to play with expression off, but when the Themodist is on, it doesn't work. That isn't too hard to figure out. We'll do it.
By the way, before we get into this, I have a question. There is no such thing as a Themodist with only one theme nipple to the bass theme port and nothing to the treble. Are you sure you aren't looking at the sustain pedal, instead? Your hammer rail is probably split and operated by two mechanical levers instead of two soft pedal pneumatic/valve sets, but I'll ask you anyway. I want you to locate each element of an expressive player piano for me, and tell me where they are, and what they look like. The elements are:
1) Motor governor,
2) sustain pedal pneumatic and valve,
3) soft pedal mechanism (type),
4) Themodist system (separate bass & treble, or all in one box type of thing),
5) stack cutout (type and location). Anyway, now, back to the troubleshooting.
The Themodist sits between the pumps and the stack in the supply line. There will be two sections of it: one for bass, and the other for treble. There may be two pouches inside which shunt around the Themodist when not in use, or (more likely) a sliding pallet valve, operated by an external pneumatic and its valve. If the player doesn't play on Themodist, first locate the device that contains it. The pump vacuum passes through it on the way to the stack. Remove it (you may find it attached to the underside of the keybed). Get a vacuum supply to test it, put a gauge and a 5/32" leak tube on the output(s) by drilling a rubber cork and inserting these things into them, and then test the device.
Start with knotted rubber tubing on each of the theme nipples going to the stack. If there are theme valves needed to drive these, then remove the theme valves too. Put them all on the bench. You have it all right there in front of you. As you open the tubes which normally led to the tracker bar, you see the gauge jump up to something close to the pump supply pressure. When you close a nipple, it drops down to a _preset_ amount. If the preset amount is too low, there is a way to change it. You may have a spring regulator (in-line knife valve or starvation valve of some kind) on the device that can be adjusted. If the spring is too weak you can adjust it, but first, just pull open the moveable leaf by hand and see if that doesn't do the trick. Somebody can pump while you do that, before you remove the Themodist.
If this isn't the problem, I suspect that either a hole or port got covered by mistake during the rebuild, or you have some other very simple problem. A Themodist is simplicity itself.
You won't have any trouble finding it. So as you look, keep us posted. Who knows, maybe somebody on this page has seen one of these things and can guide you right to the problem. But otherwise, we've got you covered! No sweat.
Craig B. |
(Message sent Wed 18 Sep 1996, 12:55:37 GMT, from time zone GMT.) |
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