>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.
>
? Perhaps there was an error in the anode-cathode (feedback)-C ? It
doesn't make sense that the 3cx1500D7 would have 4-times as much
feedback-C as a 3cx1500A7.
>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.
? Good points, Dennis. The rub with jacking up the anode-supply
potential is that most Ham-amp bandswitches are not going to be very
happy with a >3500vdc anode PS.
>
>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?
? I turn the amp on when needed to communicate. With instant-on tubes,
warmup is c. 1-second.
>Planning ahead takes care of the wait requirement.
>
? I've seen 80m West-Coast to Europe openings into that were over within
3-minutes after I turned on my transceiver.
>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.
>
? It is hardly good engineering practice to build an amplifier without
step-start.
>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.
>
? With the 3cx1200Z7 now svailable, why settle for the obsolete _A7
version?
cheerz, Dennis
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