dave wrote:

On 08/23/2013 05:33 PM, Shaun wrote:


"Michael A. Terrell" wrote in message

I built a two meter repeater on 146.01/61 MHz for my school's ham
radio club. One of the TV stations I worked at was an empty building
before I laid out the equipment room, installed the transmitter and
processing racks. That was a 1952 model TTU-25B UHF TV transmitter on
Ch. 58 that was built by RCA. Parts were no longer available from RCA,
since they were out of the broadcast business. That only made the job
slightly harder, since there had been no new final tubes made for about
20 years, and no company had managed to rebuild one that could put out
anywhere near the rated power. Nice water cooled stainless steel jugs
with 7 KVDC across the coolant. Twin 1000A 1.5V filaments that had to
be balanced by stretching copper bussbars used as variable resistors.


Didn't Comark (division of Thomson Multimedia) service RCA customers
well into the 1990s? When I went to IOT school in 1995 they still sold
RCA renewal parts. Comark bought RCA (including the rights to Nipper).
Now they are both part of Thales, a French defense contractor.


They still sold some custom uncased silver mica caps that were used
as coupling capacitors for the 4CX250 drivers, but not much else. The
custom made final tubes were made by their transmitting tube division,
and when RCA shut it down, they destroyed all the design and assembly
information. One of the old RCA Transmitting Tube manuals had a
simplified schematic, and the data sheets for the 12.5 & 25 KW UHF water
cooled power tetrodes. The transmitters were considered obsolete and
EOL, so parts that were designed strictly for that model were NLA. That
custom Mica cap was used in some RCA FM transmitters that used the same
basic chassis as the aural stage of the TTU-1 and TTU-25 series TV
transmitters. Why keep making parts for a transmitter that was
considered too low power for new builds? The two final tubes were
designed for that one series of transmitters.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.