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Post by birkie on Mar 10, 2017 14:19:39 GMT
Hi all, I took the top plate off our 1940 CF-2-H16 the other day, and found some corrosion by the foam rubber gromit where the refrigerant and power lines go into the top of the cabinet: goo.gl/photos/Gh849EMmAypvgJCN8The copper surface is roughened, but it doesn't look like there is any severe pitting that threatens the integrity of the lines at the moment. This reminds me of the foam rubber corrosion that affects later model Hammond organs; after a few decades the decaying foam rubber eats through a protective enamel layer of the wires, then dissolves the copper and causes an open circuit (I think these are tiny 40AWG wires). I removed some of the foam rubber, but left it mostly intact as I'll be moving soon and want to make sure the refrigerant lines are held securely in place for the move. In the meantime, I'm trying to think of a suitable replacement... |
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Post by ckfan on Mar 10, 2017 14:25:27 GMT
Wow, thank you for sharing that. I have never seen that happen before. I'm glad you caught it before they got ate up too bad. When I rewired my flat top I had no corrosion like that. In fact, even though the body was in rough shape the lines were squeaky clean. I wonder what chemical reactions are taking place there?
Oh, and I love Hammond organs. Just something about the rich sound that they make.
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Post by birkie on Mar 13, 2017 1:46:55 GMT
Interesting that yours had no evidence of corrosion at all. Did you keep the rubber seal, or replace it? If so, what did you replace it with?
I'm not sure of the chemistry - so many copper salts are blue or green! One thing I do note is that the foam rubber was not homogenous at all. It varied in density, and had a few white fibrous masses inside of it; the quality of the rubber was suspicious. Who knows, it could have just been a bad batch.
I too love the sound of Hammond organs. On the inside, they are fascinating - it's really neat to see how they created an electromechanical system that more-or-less parallels how real organs synthesize sounds by mixing together harmonically related pure tones.
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Post by ckfan on Mar 13, 2017 15:04:30 GMT
I kept the rubber seal but I had to cut it open to get new wiring through it and into the top section. My rubber was relatively flexible and looked to be the same consistency throughout. I didn't see any white fibrous material in the middle of it.
I honestly don't know how they work but I do know that I love the sound the Hammonds make. Don't they use some sort of spinning disk setup to vary the tones that they generate?
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Post by birkie on Mar 13, 2017 17:59:19 GMT
My foam rubber seal was mostly hardened, it seems to have been inferior material for whatever reason. Oh well, just something to check out for those with flat tops!
Re: Hammonds - yes, they have something like 96 spinning "tone wheels" with varying numbers of "teeth" that each induce a nearly pure sine wave in a nearby pickup coil (just like an individual pipe in an organ produces an almost pure tone). Each key on the keyboard has something like 7-9 contacts; each contact has a tiny wire leading to a different tone wheel representing an even or odd harmonic of the base frequency of a given key. The drawbars allow the user to selectively attenuate or accentuate particular harmonics (similar to the stops of a real organ). Fourier series mathematics shows that this allows the Hammond to roughly approximate almost any waveform. The synchronous AC motor (Hammond's secret sauce) and physical gearing made sure everything stayed exactly in tune.
Anyway, hundreds of tiny fragile wires and corrosive foam rubber do not make a happy combination! At least the corrosion my flat top will be much easier to deal with
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Post by ckfan on Mar 13, 2017 18:03:05 GMT
Yeah, your lines should be easy to clean up and protect.
I had no idea that those organs were so complex. Thank you for shedding some light on them!
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Post by blackhorse on Aug 9, 2017 17:49:05 GMT
Maybe PVC? Some rubber/plastic with chlorine in it?
I'm very careful to only use wiring from known sources for my re-wires; there's wire out there that the conductors turn green and greasy after some years. I've also seen foam tubing insulation that does that to the tubing.
Probably from the same fine people who brought us toxic drywall.....
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Post by elec573 on Aug 10, 2017 4:35:10 GMT
Not to be nasty but it looks a lot like what my copper wast lines had on them before I had them replaced? My house had all copper
lines in it even for the wast lines . I guess back then copper was cheap .
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