[Amps] Drake L7 issue

Paul Christensen w9ac at arrl.net
Fri Sep 26 21:42:12 EDT 2014


> "The L7 schematic http://www.qsl.net/ea4bb/EA4BB/Old_Radios_files/L7.pdf
shows the connection to be two lines only (2 lines and ground).  The
120V fans are connected across one of two primaries of the filament
transformer but there is *no* connection to Neutral and the only ground
connection is the chassis of the power supply (and via the power supply
cable to the RF chassis)."

By 1979, I thought all amp manufacturers knew not to use ground as a 
current-carrying conductor.  Same issue with the Alpha 70/77 series and some 
Henry amps.  The fix for the Alpha 70/77 is to use a 4-wire cord and cut one 
jumper on the male Cinch-Jones power connector.  It doesn’t even require 
getting into the amp.  To correctly convert the L7 may take a bit more work, 
but it looks manageable.   Or, live with it knowing that limitation.

Paul, W9AC




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