On Jul 16, 4:48*am, "Antonio Vernucci" wrote:
Mine has the same behavior, and the technical manual says that it's the way it
works so no problem.

Furthermore it seems rather logical as in A.M. mode the H.T.s are only
required when the mike paddle is depressed... The dynamotor speed settle time
is acceptable in this mode but try to figure out the dynamotor being turned on
and off at the keying speed in CW!

Hope this helps,

Thierry
--

Thanks for information. OK for CW, though for AM it gives me a strange feeling
to hear the dynamotor starting every time I push the microphone PTT. In the
BC-191 / BC 375 the dynamotor instead runs continuously, either CW or AM.

I have built an AC power supply for my ART-13 and I must now adapt its control
logic to that of the ART-13, which is not immediate to understand because the
schematic diagram is not easy to read (so many relays ...) and the service
manual describes things using a rather odd sentence structure, difficult to
follow. I do not succeed to get the antenna relay energized in any way, so I
fear I'll have quite a hard time in the near future to have it in working order.

73

Tony I0JX
Rome, Italy

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

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

Yes, looking to the schematic diagram, I see a relay that interrupts high
voltage (+1250VDC) on the modulator tubes plate circuit when one runs CW. So
having the dynamotor continuously running is no problem, because the modulator
tubes would draw no current anyway.

When in AM instead, there would in principle be two alternatives:

- to have the dynamotor running continuosly. But they should then have a relay
which removes plate voltage from the modulator tubes during receive, so as to
avoid a useless power consumption from the battery. Such arrangement could cause
high voltage spikes in the relay and/or modulation transformer

- 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

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