Discussion in 'Amateur Radio Amplifiers' started by KD4JBL, Jun 10, 2021.
My Heath Kit SB 200 working.
When I key radio I get a loud chatting sound from amp.
Maybe low voltage power supply capacitor is leaky.
Or using an amp that doesn't have a soft-key modification and trying to key it with a rig that doesn't have an isolated relay internally so the rig cannot pull -120V to ground and is ready to blow something up.
Good point Steve!!!! Many people burn out the switching transistors in their radios with SB220 and SB200 amps!
Need the softkey kit from Harbach.
I would suggest the softkey unit to protect whatever rig you connect to the amp anyway, but at least you may narrow down the possible causes with this simple test:
Take the amp's 'key' lead out of the rig, and short the ends of that cable to key the amp and see if it still chatters. If so, then the problem is elsewhere. You can also check the voltage across the amp's 'key' terminals and see if it is at/near specs. (-120 VDC)