SB-220 Bandswitch

[Multi-Volti Devices]

Original part number was 63-562.
>switch seems to have been a bit marginal, as contacts have tendency to
>overheat

While it's true that the switch wafer is small compared to those found on
some LARGER commercial or OLD homebrew (probably built from commercial
surplus equipment) amps,

The only ones I ever saw that showed problems were either 1) manually
'hotswitched', or 2) contacts vaporized due to probable parasitic
oscillation (see Rich Measures AG6K QST references).

The original power specification for the SB-220 was based on the old 'legal
limit' of 1 kW cw INPUT power, 2 kW PEP (2-tone SSB).

When the legal limit (hey, we all know people who ran whatever the amps were
cabable of before the change!) was changed to 1500 W output, the assumed
'common law' SB-220 power spec changed to whatever the 3-500Z's would do
with their glassy selves pushed to the limit, I think the diversity of
component failures increased.

A litte off seubject, and FYI, I think the current rating on the 54-237
plate xfmr is only 500 mA ICAS/250 mA CCS, but I'd have to dig to be sure.
That's why Peter Dahl has so many beefy (filet mignon I guess, looking at
the prices) replacements available.

I'm looking for someone to make a replacement rear wafer (-562) available at
an affordable price, but that's another one of those 'someday, some year'
projects.

Murray

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