[Central-Electronics] 10B and 20A BC-458 VFO issues

[k7fm]

Hi Jim:

A friend of mine restores old Tektronix oscilloscopes.  Tektronix had
factory retrofits for all selenium rectifiers because of the likelihood that
they would fail, filling the room with acrid smoke.  They are a failure
waiting to happen.

You can solder to aluminum.  Usually a torch is used along with aluminum
solder.  After the aluminum is heated, it must be scraped with a stainless
steel brush.  Doing that the solder will flow nicely.

In the aircraft, up to 14 volts was placed on the tube filaments with no
concern.

DC on the filament is very helpful in the ARC-5.  The cathode of the 1626 is
above ground and tends to him modulate when ac is used.

I built a solid state heterodyne vfo out of a basket case BC-221.  It is a
jewel.

73,  Colin  K7FM