[BC] Dud 4CX20,000 ?

[donroden at hiwaay.net]

Quoting Milton Holladay <miltron at att.net>:

> You need to specify the letter suffix, which I would guess to be C, as
> the 35 uses a D, but, for all I know, might be A or B........(been ~20
> years since I worked on a 25)
> M

The correct designation in the book is a 8990 ( 20,000A )
the A / B / C / E   are all 10v at 140A filaments.

the D version is a 9015 ( 20,000D ) and is rated 7.5v at 145A filament.

Unless there are things drastically different between the A, B, C, and E
versions, I believe all would work... maybe some better ( ?? )

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.

Anyone who has fought this dragon is welcome
to offer suggestions ( consolations ).

Don R

ps...
and yes, for a few more $K I could probably find a nice Z5 or similar.