A quick overview of the 1978-era SB221 amplifier brought back to life in May 2016 after being on a shelf for more than a decade.
Details about the project are at:
va7st.ca/2016/0...
Work done to this amplifier included:
- replaced filter caps (with 330uf 470V)
- new 2016-design Harbach RM-221 meter board
- new soft-start inrush current board Harbach SS-220
- new high-flow fan blade
- new AG6K parasitic suppression kit (incl. 10-ohm "glitch" resistor in place of RFC-2 on B+ line)
- lots of rewiring to fix many issues found inside
- directly grounded grids
On the front panel, you'll see a small toggle switch. That's a standby switch with a red LED beside it (lights up when keying line is on), and an ALC adjustment knob.
Previous owner changed the old 110V T/R and bias relay to a 12VDC relay, so no soft-key mod needed for modern transceivers -- my FT-2000 keys the 14.5VDC line very nicely.
The amplifier will be used in CW and RTTY contesting (some SSB work, too), and DX chasing at VA7ST.
If you like radios and ham radio contesting, check out the Zone Zero podcast at zone.va7st.ca.
8 сен 2024
