HW-101 mica cap voltage ratings

[Keith Rowland]

Jim:  You should be perfectly safe using 500-volt micas anywhere except
in the transmitter plate circuit, where the plate RF bypass cap (if it's
a mica; I don't remember) should be at least 1000-volts.  I don't recall
what Heath used as a plate blocking cap, but remember it has to
withstand at least the final plate voltage, and high RF voltages as
well, so I personally would use a high-voltage doorknob cap here, or a
ceramic transmitting-type cap, such as the 5000-v or better units that
RF Parts and other companies sell.

73,

Keith



Jim Glover wrote:

> Hi, Heath enthusiasts!
>
> At a hamfest last year, I pleased myself by finding an HW-101
> (the transceiver I learned the ropes on back in '76) for $100.
> It worked OK at first... a little bit of flaky behavior, but
> not too bad.  It's steadily developed new problems, though.
> I successfully traced one of them to a bad pot, but haven't
> been able to find all the problems.
>
> Someone from another list I belong to suggested that I look
> at resistors, especially high-value ones, which may have
> crept up in resistance over the years, and at (here's the
> point of this post) mica caps.  Lately, this thing has
> developed some symptoms which could be explained if some
> of the mica caps were going bad, and so I'd like to try
> replacing the mica caps.  The thing is, I can find values
> for the capacitance of the mica caps in the circuit, but
> not the voltage ratings.  I have an HW-101 owner's manual,
> which has both a circuit diagram, and a parts list, but
> both giving only the capacitance ratings, but not the
> voltage ratings.
>
> Can anyone tell me how to find out, or guess accurately,
> about the voltage ratings of the mica caps, so that I can
> get replacements?
>
> Thanks!
> --Jim  WB5UDE
>
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