On Jul 18, 8:30*pm, "Antonio Vernucci" wrote:
I have the ART-13's 1950s descendant, the Collins 618S (ARC-38). This
has the same dynamotor behavior as the ART-13 - it runs continuously
when in CW mode. This is quite normal; when in AM mode the dynamotor
runs *only* in xmit mode. In the 618S B+ voltages for the xmit and
modulator
are generated by the dynamotor, B+ (and B-) for the rest of the system
is derived from the 115V 400 Hz supply. On my 618S I run the filaments
from a filtered 27.5V DC supply, the dynamotor from raw DC. This is
accomplished by minor rewiring of the 416W-1 power supply; it's
probably easier on an ART-13.

John VK3XAO



- to instead have the dynamotor running only during xmit

Evidently they selected the second one.

As to the power supply, I preferred to build a power supply fully replacing the
dynamotor which is too noisy. Anyway feeding the dynamotor with raw (unfiltered)
DC seems to me a good idea if one wants to use the dynamotor without a battery.

73

Tony I0JX

Understand your desire not to have dynamotor noise nearby. The 618S
dynamotor is rather smooth and quiet, to me at least. When installed
in Boeing 707's, the dynamotor power supply 416W-1 was replaced by a
208V 3-phase 400 Hz input power supply, the 416W-3. More reliable than
416W-1. DC input to the dynamotor is ~ 20A @ 27.5V DC from a 27.5V
750W supply - no batteries in the system.

John VK3XAO