Hot Rod Mic - More Details

[elliott@xxxxxxxxxxxxxxxxxxxxxxxx]

Harpers,

Here are some updated details on the Hot-Rod/Crystal Balls mic.
I have checked this information and re-checked it at least 5 times.
So, all of this info should be correct.

THE POT
-------
It is 5 Meg, and much to my surprise, it seems to be a linear taper.
As I said before, I've put several volumes on Astatics and Shures, and
I've always used audio taper; however, I've never used a capacitor.
Also, one minor note about the markings on the pot.  It had a 'C' w/a
circle around it (like the copyright symbol) and 'B5M'.  I left out the
'B' in my previous post.  (Does anybody know if that signifies linear taper?) 
Also, when playing thru the mic, w/the volume on the bottom, turning
the volume knob from the right to the left (counter-clockwise) will turn
up the volume.  With a linear pot is shouldn't matter if you wire it up
the other way around, but with an audio taper pot (w/o the capacitor at
least) it would matter.  With all the audio taper pots I've used in
the past, it has worked the same way (counter-clockwise to turn up
the volume).  

The CAPACITOR 
-------------
OK.  I measured the capacitor, and it is .15 ufd  (AKA 150 pfd) ceramic cap. 


The SCHEMATIC
-------------
The schematic I entered earlier was correct.  The element is connected to the
two outside leads of the pot, and the capacitor is connected between the
center lead of the pot and the outside lead of the pot that is connected to
the positive side of the element.  Here is the schematic again....

                             Capacitor (.15 ufd)
                               | |
             ------------------| |--- 
           /  \          \     | |  |
           |  |          /          |
 Element-> |  |      Pot \          |
           |  |    5 Meg / <--------------  to hot lead           
           |  |          \                  on the connector 
           |  |          /           
           \ /___________\           
                    |
                   ---
                    -
                 ground

Here is another representation of the same thing.  This is a drawing looking
down at the bottom of the pot (so the pot is bottom side up w/the shaft
pointing down.

              Positive
              Lead of 
      Frame   Connector 
      Ground      |         Capacitor
            \     |/--()--/
             \    |     /
      ---------O__O__O----------
      |       /       \        |
      |      /  CB5M   \       |
      |      \  (pot)  /       |
      |       \_______/        |
      |                        |
    Negative              Positive
    Lead of               Lead of 
    Mic Element           Mic Element
 
And here's one last attempt to describe it.  Here are the connections:
 Far left lead of the pot: frame ground AND mic element ground
   Center lead of the pot: positive lead of connector for the amp cord AND
                           one leg of the capacitor
Far right lead of the pot: positive lead of mic element AND the other leg of
                           the cap

Assembly Details
----------------
The volume (pot) shaft comes through the shell of the mic where you would
screw the mic to a stand.  There ALMOST isn't enough room for a fullsize
pot there.  It is VERY, VERY close... in other words, you may run into problems
if you try to put a full size pot there.  If possible, try to get a mini-pot.
Just didn't want to mis-lead anyone into thinking that this isn't tricky.
Before you start drilling holes in your favorite vintage JT-30, try to
make sure it will fit first.  Or, if possible, experiment on a mic that isn't
as important to you.


That's about all I can think of to tell you (and then some) about this mic.
If I left something out or screw something up, let me know.

Elliott New