Mark - See below ...
Mark Nace wrote:
I have saved up a few mundane questions for the Drake folks. Instead of separate emails, I will just ask them all in one: 1. The early AC-3 power supply had some sort of choke filter for the +650 volt section, right after a bridge rectifier looks like. My buddy has one of these actually. can someone explain it briefly, and tell why it was changed out (cost perhaps)?
Cost was a factor I'm sure, also shipping weight, but essentially with the larger filter caps the ripple was more than adequate for the FINAL Plate supply.
2. In the TR-3, does anyone know why it was designed to require going back and forth from SSB to Xcw to transmit and receive CW? I got out one of my TR-3's and re-discovered this, and after looking at the manual, found it was true. Pretty inconvenient, and probably pretty hard on the switch over time.
It was designed as a SSB transceiver, primarily for mobile use, and CW was only included as an afterthought.
3. When putting new diodes in an AC-3 or AC-4, is it recommended to add speed-up caps and equalizing resistors across the diodes?
No. Modern diodes are consistent enough that these "equalizing" components are no longer required. Some will argue with this, but no new designs (roughly the last 20 years) have them.
4. When working across a band on TR-3's or TR-4's, I usually just peak the Rf tune, but wonder how far one should go before re-dipping again in the same band.
ALWAYS ALWAYS ALWAYS dip the Final plate current _LAST_ , and with any change in frequency. The very thing that made Sweep tubes so popular, high perveance or high plate currents at low voltages, makes them very sensitive to off resonance operation. Again, ALWAYS dip the Plate current last, and every time.
Thanks for listening, and thanks for all the good advice over the years.
73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs <www.k4oah.com
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