Bionic Chicken's post is exactly correct as to the modification. If you have an early model Mark III made prior to Feb 1977, than the stock capacitor (C66) will be 20 uf @450 volts. The discharge time of this cap caused the receiver's speaker output to remain on for several milliseconds when the transmitter was keyed up and the resulting feedback caused the unit to "ping" or squeal. In Feb '77 the FCC made Browning eliminate the "ping" so C66 was changed to a 2 uf @ 450Volts for late model Mark IIIs. Several Eagles that I worked on had C66 removed and a 3 position switch installed on the receiver's rear skirt, which allowed either a 2 uf, 20 uf, or 40 uf cap to be switched in to change the length of the ping. As BC said, exceeding 40 uf is really tough on some of the components, and is not recommended.
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