RA17 page 8

The 100KHz unit (3rd IF) is the largest of all the removable units, forming the complete left side of the chassis and containing the 100KHz amplifier stages (V14 & V16), the 100KHz rear panel buffer amplifier (V17), AGC and detector circuitry (V18 & V21) and BFO (V19) as well as the Crystal Filter module and the 100KHz Filter module. This huge unit was already partially refurbished when replacing a burned out resistor and investigating the AGC circuit operation. The spindle can be removed for easy access to the tag-boards, see below.

100KHz Tag-Boards complete with only the buffer amplifier remaining . . . (far right)

It is easy to overlook those capacitors and resistors hiding away within the metal cans. The two filter units are no exception, there being a couple of resistors within the 100KHz unit which can be reached with minimum disturbance. However those within the Crystal filter are not so easy to reach. I decided to leave them since experience was already showing that only those resistors carrying significant current were likely to be out of spec. The BFO was not forgotten and proved a fiddly little beast to work on.