Corsair II Display Problem & Fix

From the Ten-Tec Reflector November 5, 2006

Two weeks ago during the CQ WW DX contest I suddenly lost my display on the Corsair II. The internal keyer also ceased functioning as well (the keyer and display are controlled by the same processor). Turning the Corsair off and then on again resulted in a blank display (except for the decimal point). In all other ways the Corsair II worked correctly. Turning the Corsair II off for 20 minutes or more brought the display back to life… for a while. I did notice that it took up to 10 seconds or more from the time the Corsair II was turned on till the display initialized itself. Before its initial malfunction the display always initialized with a second or less.

An investigation of the display circuit pointed to three suspects… U10 the display processor, the 4.05 MHz crystal, and C6 a small electrolytic capacitor that provides a reset pulse on power on. As the frequency display was stable and accurate until the freeze I didn't think the crystal was an issue. The processor was still a suspect but it made sense to check the capacitor first. I removed C6 (connected to pin 28 of U10) and upon testing it I obtained very erratic capacitive readings. I replaced C6 with a known good 2.2uf/50 vdc electrolytic.

The Corsair II's display now initializes correctly and shows the operating frequency in about one half a second from power on. Since this repair there have been no further display lock up incidents.

Perhaps this may be of value to other Corsair II owners. If your display is initializing more than a few seconds after power on this capacitor is probably changing values and that is a good precursor to the problem I just experienced.

73,

Jerry, KG6TT