[BC] Dud 4CX20,000 ?

[Rob Landry]

On Sun, 5 Feb 2012, donroden at hiwaay.net wrote:

> 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.

Depending on your TPO you may need something closer to 500 watts, but that 
is definitely the way to go.

> 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 ran an FM-25K at WCRB from 1985 to 1997, and then moved it to Cape Cod 
as a backup for WFCC. I don't recall a lot of problems with the control 
logic; mstly it was the IPA that gave us fits.

Even the IPA was pretty reliable for the first ten years; after that it 
got very squirrely.

> 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.

Assuming the transmitter is in reasonably good shape, I would defer that 
for the moment, replace the IPA and see how well the transmitter works.

Rob