I made a similar mod to my 229B tuner. However, instead of using
doorknob caps I replaced the originals with 6KV 470pF Y5P ceramics.
These capacitors are physically larger than the originals, having a
thicker dielectric for increased breakdown voltage and larger plate
surface area for increased current carrying capacity. The drift problem
was nearly completely, but not entirely, mitigated. Complete
disassembly of the tuner was unnecessary, since I was able to work in
the tight space around the switch with small forceps.
Now, I'm considering using the doorknob caps. Would appreciate any
suggestions about disassembly of the tuner for easier installation of
the doorknob caps.
73,
Jack K1VT
> I few months back, I modified my TT 238 tuner by changing out the disc
> ceramic
> caps with surplus Soviet military doorknob caps, which dramatically
> improves
> the power handling capability on 160 and 80 meters. Heating used to
> cause the
> SWR to 'drift', even at 100 Watts in some situations on 160. The mod
> worked
> well, and if anyone is interested, I have all the details and pictures
> on my
> website at www.n6ie.com.
>
> 73,
> Ron N6IE
> www.N6IE.com
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