Amateur Radio Related Articles
Additional info and articles.
- Category: Amateur Radio Related Articles
Heathkit SB200 Linear recapping/ power supply rebuild
Many of the old vacuum tube radios and amplifiers can be brought back to useful service by replacing the
components that go bad with time, such as electrolytic capacitors and the old "paper/foil" types with the
more reliable modern repacements. Once that is done, a full power test can be done to ensure that the
unit has been brought back to full functionality. Amps like this this can be an ecconomical way get some power to compenstae for the poor band condtions.
Be aware, though, the "oldies" need either modification or adaption of the keying system to work with a modern rig interface. The voltage present at the SB200 keyer will "smoke" the internal driver transistor on that nice new radio.
In the picture below, it can be seen that the new capacitors are only a fraction of the size of the originals,
but actually have a slightly higher voltage rating and current handing capability! The diodes were also replaced with better rated types for good measure . The bleeder network/bias resistors were all still in good shape so they were left alone.
If you do aquire a unit like this, I highly reccomend that you check the caps , diodes and resistors before doing a slow first time power up with a variac at minimum. Better yet, just replace them, because a sudden catastopic failure could possibly destroy the power transformer... and that is a much, much more expensive proposition...