[BC] Dud 4CX20,000 ?

[Sid Schweiger]

Don Roden writes:  "I've been asked to look into the possibility of reviving an old 25K that has been sitting at the studio (air conditioned ) for over twenty years to be available as an EMERGENCY transmitter .... not a standby.

"The MS-15 exciter and the famous ( infamous ? ) eight combined IPAs will be replaced with a 300watt solid state transmitter.

"As I understand it, the FM25 had a clunky control system and was prone to come up in different states than intended ... ie: plate off sometimes turned off the filament too  ( a service bulletin was issued ).

"I am considering changing the control system out in favor of a simple plug-in relay control ladder using more modern 3 phase loss protection and plug-in time delays."

I took care of one of these beasts for ten years.  I never encountered any problems with the control ladder, but I did replace the IPA with Harris' recommended solid-state replacement and the MX-15 exciter with a Digit CD.  I also had to replace the plastic-link IPA drive control (a royal PIA, but quite necessary and rewarding in the end).

Best advice I can give is to beg, borrow or purloin a copy of the FM-25K Service Supplement.  If nothing else, you'll learn a lot...but you'll also have a ready reference to most of the service bulletins for that rig in one place.  I'm not sure Harris has it online, but there are plenty of copies floating around.

Sid Schweiger / IT Manager, Entercom New England