As others have said, it's a protective 'fuse' for the receiver in the
TR-3/4 series transceivers.
It's a worthwhile addition because again, the TR-3/4 series is an
EXCELLENT 'SSB Transceiver for _Mobile_ operation'. It's marginal for
other uses, but for it's design goal, terrific!
Mobile use is WHY the bulb is necessary. You won't have an 18-wheeler
carrying a 2 kW CB transmitter pull up next to your home shack, but....
Even a 200 W transmitter with it's vertical antenna only a few feet
away from yours can fry an input transformer.. I have seen the bulb in
a TR-4 show a good glow with another nearby 200 W transmitter on a
different antenna and band.
The #12 bulb is identical to the #47 bulb electrically, just with
shorter leads. They are readily available from the on-line bulb
dealers, and shouldn't be replaced with a piece of wire, especially if
operated mobile.
Obviously an open bulb or even corrosion on the leads can severely
impact receiver sensitivity, second only to that %%#%$ 'TCVR/RCVR' slide
switch on the left side!
73, Garey - K4OAH
St Charles, IL
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Neil M Califano wrote:
What is this???:
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