The following modification details and pictures are of the QSK modification W2NO installed into his Amertiron AL1200 RF Amplifier.
One Jennings Vacuum relay was used for RF output and two high speed RSD-12V micro-reed relays were used for RF in and BIAS switching. The two RF relays were mounted together on a new fabricated "L" bracket mounted in the location where the original T/R relay board was removed next to the chassis SO-239 RF connectors. The BIAS relay is mounted above the amplifier's EBC board on a standoff using a piece of perf board.
A +24VDC external self-contained type computer power supply was added under the HV power supply capacitor bank to speed up the 12v coil on the Jennings relay. A 75 ohm resistor was added in series with the Jennings relay coil to limit the coil current to 150ma. This will insure the Jennings vacuum relay will switch fast enough, and boy does it ever. The two RSD-12V micro-reed relays and the SEQ-QSK sequencer are powered from the amplifier's +12VDC internal power supply.
The SEQ-QSK sequencer is programmed to 3ms timing steps. This provides no SWR bumps or hot-switching when keying the RF amplifier.
The original amplifier's bias cube relay was really loud, so it was also changed to a quiet reed relay capable of 200v a 1A switching. Now there is 100% total silence when all relays inside the amplifier switchover.
All finished and works like a DREAM! Here are the final assembled pictures:
For additional information on how the RF and BIAS relays, and the SEQ-QSK are wired together, reference the Henry 2K-4 QSK web site for a wiring example. Your wiring installation may vary, so adjust accordingly to the Ameritron AL1200 schematic.
For more information about this Ameritron AL1200 QSK modification, email your questions or comments direct to Dan W2NO via his http://qrz.com email address