The Zener is a 13v. However it will work with a 12v which is easier to find.
The actual voltage is not critical as long as it will calibrate. You can add
a 1N4000 diode in series with the Zener if you need a little more voltage.
I removed R2 (180 ohm) and the zener and replaced them with a 7812 when I
installed the RotorEZ interface. It provides a little better regulation. You
can also add a 1N4000 on the ground side of the 7812 and it will raise the
voltage to about 13.2v.
Another advantage: the 7812 will provide sufficient current to support a
couple of LED's for the meter light if your dial light burns out.
73s de Jim
> -----Original Message-----
> From: email@example.com
> [mailto:firstname.lastname@example.org]On Behalf Of Todd Coulter
> Sent: Thursday, January 26, 2012 6:52 PM
> To: TowerTalk@contesting.com
> Subject: [TowerTalk] Ham II Control Box
> I am trying to replace the zener diode in a Ham II control box,
> but I am not sure exactly what it is. The markings on it are
> "13VR". Can anyone tell me what this crosses to (Specs?) so
> that I can hopefully run to the local Radio Shack and pick up a
> replacement diode. Thanks.
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