On 4/23/2009 10:12 AM spake thus:

Anyway, here's a shot of the pedal's guts, with some labels to help
clarify.

http://i151.photobucket.com/albums/s...y/P4231021.jpg

1. Spring and Linkage. This is pressed downward when the pedal is
depressed.
2. Brass Linkage/Contact. This moves to the right via linkage 1 when
the pedal is depressed.
3. Copper Contact. This moves to the right and toward the graphite
contact on the left end of the Carbon Pile when the pedal is
depressed.
4. Carbon Pile. This is a long ceramic tube filled with ~100 graphite
discs and a graphite contact on either end.
5. Bypass Contact. When the pedal is fully depressed, the Brass
Linkage touches this contact and bypasses the Carbon Pile.

Now - here's what I didn't mention previously... I got this thing in
pieces at a garage sale, along with the sewing machine. The previous
owner had dropped the pedal, cracking the bakelite and spilling its
innards all over. He assured me nothing was missing, and when I
fiddled with it, it all seemed to fit into place (as shown). BUT, I'm
not 100% sure I'm not missing something, and I'm also not 100% sure I
have it assembled correctly. The Copper Contact was as shown (nearly
straight) when I got it - it doesn't make contact with the Carbon Pile
until the Brass Linkage is nearly touching the Bypass Contact. Also,
the slot where the Copper Contact and Brass Linkage tie together is
held together very tenuously - I'm afraid it's going to fall apart
every time I fully-depress the pedal.

So what I could use here is an evaluation of the parts and placements
- do I have everything? Is it all in the right place? I can't figure
any other way to set it up. Any other thoughts?

Pretty clear how it works now; as someone described up-thread, the pile
of carbon discs gets compressed, reducing their resistance. So obviously
this happens when the spring on the left (3) pushes on the metal stud at
the left end of the ceramic tube.

So apparently the problem is either that the carbon discs aren't making
enough contact with each other inside the tube, or are contaminated, or
that there's not enough pressure being exerted on the left end of the
tube by that spring. Which could mean that either it's not put together
correctly, that there's a part missing (though I can't see where), or
that something needs bending or some other adjustment to work correctly.


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