[Amps] 3CX1500D7

[dajs at accnorwalk.com]

The development of a new power amp tube always creates a lot of interest and
excitement in the ham community. It's too bad Eimac
pulled the info from their website. Their development and marketing people might
benefit from the discussions about the new tube.

The actual spec sheet is still available. Just go to the Amp Archives for March
16 "3CX1500D7 Spec Sheet" The compressed file is 1.24 mb and consists of 4 gif's.


IMO, this tube will have limited appeal for the ham market. The
type acceptance process discourages new amplifier dessigns. As for retrofits,
how many hams are willing to cut the sheet metal in their commercial amps to
install the air socket, required chimney, and blower? The TL-922 has its 3-500z's
in series and
would require an additional 5 volt transformer. Finally, the plate voltage available
in most 3-500Z amps run from about 2700 to 3300 volts which as Eimac has already
said is low for good
performance of the new tube.

As far as instant on is concerned, it's not that big of an
advantage. Two of my four amps (all Eimac powered) have at least 3 minute wait
times. How many hams really turn the amp on and off between QSO's? Planning
ahead takes care of the wait requirement.

Page 4 of the 3CX1500D7 spec sheet states "This tube is designed for commercial
service, with no more than one normal off/on filament cycle per day." I wonder
if the warranty will be
voided if the amp does not have filament soft-start circuit.

Eimac should be commended for the effort to develop new tube designs. Unfortunately,
economics dictate high volume sales and raise the question of whether the 3CX1200A
series will soon be
discontined.

Dennis W0JX  



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