The Control Board

On my previous amplifier projects, especially the solid-state ones, most design and build effort was taken up by the control and protection circuitry. However, this is considerably simplified these days by the availability of pre-designed control boards that just need to be assembled. I tracked down two products.

The first is from available from WD7S Productions.

The WD7S triode control card

This is a super design and works in partnership with a really smart LED-based display card. I would absolutely recommend this for a desk-bound design, but there is no room for such a display here I'm afraid! Next year's project maybe! Incidentally, you can virtually buy a complete kit to make an amplifier from WD7S and there are some super completed project photos to be found in the gallery on WD7S's web site if you need inspiration. Take a look at the end of this article for other 6m amplifier designs that can be found on the web.

G3SEK's Triode control board kit

Nearer, to home, Ian G3SEK has been selling a triode control card as a kit of parts for several years and I decided to try this for the first time. This design has the following features according to Ian's sales material:

• Simple wiring to one compact PC board
• Protects your triodes, and help them deliver a high-quality signal
• Easy to build � detailed 'how-to' instructions in 38-page User Manual
• Highest RFI immunity � high-level CMOS logic, extensive RF filtering, ground-plane shielding
• Designed for 'key-down forever' reliability
• Compact � only 5.7 x 3.3in (145 x 84mm) 
  Tried and tested � over 200 in use world-wide, with many different tubes!

and includes:

• Cathode bias supply:  adjustable 3-30V, precision regulated up to 2.5A or more
• Grid and anode current metering, with meter protection
• Status output to four LEDs
• Relay TX/RX switching
• Warm-up timer � also controls your High Voltage supply
• Grid current and HT monitored � protects sensitive grids from overdrive
• Anode current monitored for surge protection � also controls mains to your HT supply
• 12/24V DC supply for external relays.

Further information on the board can be found G3SEK's web site.

• An unpopulated board board can be bought from here.

• A kit can be bought from Down East Microwave in the USA.

Completed Control Board

And, boy, does its use simplify the design! I decided to use Ian's board for my amplifier.