[R-390] Audio Sub-chassis Break-in relay mod

[gary.biasini at shaw.ca]

On a Teledyne Systems audio sub-chassis on an R-390A of mine there are some
mods of unknown purpose.  I am attaching a schematic of the mods and 2
pictures - I don't know what the Motorola part is (a transistor?) so it is
shown as a circle on the schematic.  Essentially, the original connections
to the coil of the break-in relay K601 (terminals 1 and 7) are removed and
parts as noted on the attached schematic are added to each side.

 

Does someone recognize this modification or can you reverse engineer the
purpose?

 

Thank you for considering this.

 

Gary

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