Description
''Simplex'' brand mica capacitors were Australian made, and used in many different makes of Australian domestic radios in the 1940's,1950's, and early 1960's.
They were not used in radio receivers made in North America, the UK, or Europe.
''Simplex'' mica capacitors used in my 1958 HMV valve radio ranged in value from 10 picofarads to 460 picofarads (or more) with four 100 picofarad capacitors used inside the two IF transformer cans on top of the chassis. (Two inside each can).
According to AI : ''Simplex mica capacitors were not as 'reliable' as mica capacitors made in America or the UK'', but so far, I've only heard that from AI. (It may or may not be true)
Most radio restorers usually recommend to ''leave the mica capacitors alone'' and just change the electrolytic and paper (wax) capacitors.....unless your vintage valve radio experiences ''silver mica disease'', which manifests itself as a sudden burst of noise or crackling in a radio that seemed to be working okay.
If the faulty mica capacitor is located inside an IF transformer, replacing one of those will require an RF and IF re-alignment of the receiver
In 1949, Ducon Condenser Ltd. wholly acquired Simplex Products Pty Ltd of Sydney, but the mica capacitors continued to be produced under the Simplex name. Ducon continued manufacturing standard capacitors as well as electrolytics under the Ducon name.
By the mid 1970's, Ducon capacitors were no longer being manufactured, and Simplex mica capacitors had long since disappeared.