(per request)

On an ARC-5 Power Supply:

First- there are three "flavors" of transmitters commonly
lumped under the name "ARC-5"
The first is the Navy ATA, second is the Army SCR-274N
and last is the Navy AN/ARC-5.
The rear connectors and wiring for the ATA and SCR-274N
rigs are identical. The AN/ARC-5 connector is
physically different and the wiring is also somewhat different.
If your transmitter is black wrinkle painted and
has a big RF choke next to the tank coil, it's
AN/ARC-5. If it's black and has not such coil,
but has an anchor in yellow paint on the back skirt,
it's an ATA. If it's silver, it's a later SCR-274N.
If it's black, has no RF Choke and has a "BC-4xx"
number on the back skirt, it's SCR-274N.

Transmitter Plug Pin-out:
(Note: If yours has an octal socket or anything
other then the 7-pin Mica connector,
then it's a modification and all bets are off.)

For AN/ARC-5-
There are seven pins. The pin in the center is
pin #7. Locate the pin that is grounded
to the chassis. This is pin #4.
Count the others *clockwise* around accordingly.

1. No Connection
2. +200VDC for the Osc. (needs to be right for stability).
3. Keying Relay (ground to key).
4. Ground.
5. A+ 24-28 VDC.
6. PA Screen Voltage (use 20K 5W dropping res. from B+).
7. PA Plate B+ Voltage +550VDC

For ATA/ARA and SCR-274N:
There are seven pins.
The pin in the center is pin #7.
Locate the pin that is grounded
to the chassis. This is pin #1.
Count the others *clockwise* around accordingly.

1. Ground
2. Test point for PA grid current.
3. +200VDC for the Osc. (needs to be right for stability).
4. PA Screen Voltage (use 20K 5W dropping res. from B+).
5. Keying Relay (ground to key).
6. A+ 24 VDC.
7. PA Plate B+ Voltage +550VDC.

The best way to get power to the rig is the way the
original engineers intended. I don't mean a dynamotor-
I mean a good, solid 550 VDC source and a divider.
Both the AN/ARC-5 and SCR-274N units derive their voltages
using a voltage divider network. We'll draw a divider that
matches the one used in the original power supply.
I very much recommend it.

Primary power should be 24-28 VDC at about 2.5 amps for relay
and filiments and B+ of 500-600 VDC at about 200 MA.
We will assume the designer's specs of
550 VDC B+ and 26 VDC filiment.
Get a pencil and a piece of paper. Follow along:

Place a dot on your paper and call that point "A".

Draw a line right to point "B".
From point "B", draw a line down and

connect a 20 K-ohm, 5 watt resistor here.
Call the other end of this resistor point "C".

Draw a line right from point "B" to point "D".

From "D", draw a line downward
and connect a 15 K-ohm, 10 watt resistor.
Call the other end of this resistor point "E".

From point "E", connect a 100 K-ohm 1 watt resistor to ground.

Draw a line right from point "D" to point "F".
Draw a line right from point "E" to point "H".

+550 VDC in at point "A".
+550 VDC out to PA plates at point "F".
+270 VDC out to PA screens at point "C".
+200 VDC out to Oscillator at point "H".

Bypass all outputs with about .01 ufd to ground.

If you wish to regulate the screens for AM,
connect an 0D3 VR tube with a .5 ufd at 300VDC
cap across it between point "C" and ground.
This will bring the screen down to 150 volts.

If you use this network, and use correct antenna
matching, you will be able to properly load and
tune your command set transmitter to rated output.

Voltages lower then 550 VDC will work just fine
with the same network. Voltages much higher will
cause MO drift and increase chirp.

GL OM DE Dave AB5S

Thats handy info Dave. Thanks.

Dan/W4NTI

"David Stinson" wrote in message
...
(per request)

On an ARC-5 Power Supply:

First- there are three "flavors" of transmitters commonly
lumped under the name "ARC-5"
The first is the Navy ATA, second is the Army SCR-274N
and last is the Navy AN/ARC-5.
The rear connectors and wiring for the ATA and SCR-274N
rigs are identical. The AN/ARC-5 connector is
physically different and the wiring is also somewhat different.
If your transmitter is black wrinkle painted and
has a big RF choke next to the tank coil, it's
AN/ARC-5. If it's black and has not such coil,
but has an anchor in yellow paint on the back skirt,
it's an ATA. If it's silver, it's a later SCR-274N.
If it's black, has no RF Choke and has a "BC-4xx"
number on the back skirt, it's SCR-274N.

Transmitter Plug Pin-out:
(Note: If yours has an octal socket or anything
other then the 7-pin Mica connector,
then it's a modification and all bets are off.)

For AN/ARC-5-
There are seven pins. The pin in the center is
pin #7. Locate the pin that is grounded
to the chassis. This is pin #4.
Count the others *clockwise* around accordingly.

1. No Connection
2. +200VDC for the Osc. (needs to be right for stability).
3. Keying Relay (ground to key).
4. Ground.
5. A+ 24-28 VDC.
6. PA Screen Voltage (use 20K 5W dropping res. from B+).
7. PA Plate B+ Voltage +550VDC

For ATA/ARA and SCR-274N:
There are seven pins.
The pin in the center is pin #7.
Locate the pin that is grounded
to the chassis. This is pin #1.
Count the others *clockwise* around accordingly.

1. Ground
2. Test point for PA grid current.
3. +200VDC for the Osc. (needs to be right for stability).
4. PA Screen Voltage (use 20K 5W dropping res. from B+).
5. Keying Relay (ground to key).
6. A+ 24 VDC.
7. PA Plate B+ Voltage +550VDC.

The best way to get power to the rig is the way the
original engineers intended. I don't mean a dynamotor-
I mean a good, solid 550 VDC source and a divider.
Both the AN/ARC-5 and SCR-274N units derive their voltages
using a voltage divider network. We'll draw a divider that
matches the one used in the original power supply.
I very much recommend it.

Primary power should be 24-28 VDC at about 2.5 amps for relay
and filiments and B+ of 500-600 VDC at about 200 MA.
We will assume the designer's specs of
550 VDC B+ and 26 VDC filiment.
Get a pencil and a piece of paper. Follow along:

Place a dot on your paper and call that point "A".

Draw a line right to point "B".
From point "B", draw a line down and

connect a 20 K-ohm, 5 watt resistor here.
Call the other end of this resistor point "C".

Draw a line right from point "B" to point "D".

From "D", draw a line downward
and connect a 15 K-ohm, 10 watt resistor.
Call the other end of this resistor point "E".

From point "E", connect a 100 K-ohm 1 watt resistor to ground.

Draw a line right from point "D" to point "F".
Draw a line right from point "E" to point "H".

+550 VDC in at point "A".
+550 VDC out to PA plates at point "F".
+270 VDC out to PA screens at point "C".
+200 VDC out to Oscillator at point "H".

Bypass all outputs with about .01 ufd to ground.

If you wish to regulate the screens for AM,
connect an 0D3 VR tube with a .5 ufd at 300VDC
cap across it between point "C" and ground.
This will bring the screen down to 150 volts.

If you use this network, and use correct antenna
matching, you will be able to properly load and
tune your command set transmitter to rated output.

Voltages lower then 550 VDC will work just fine
with the same network. Voltages much higher will
cause MO drift and increase chirp.

GL OM DE Dave AB5S

Thats handy info Dave. Thanks.

Dan/W4NTI

"David Stinson" wrote in message
...
(per request)

On an ARC-5 Power Supply:

First- there are three "flavors" of transmitters commonly
lumped under the name "ARC-5"
The first is the Navy ATA, second is the Army SCR-274N
and last is the Navy AN/ARC-5.
The rear connectors and wiring for the ATA and SCR-274N
rigs are identical. The AN/ARC-5 connector is
physically different and the wiring is also somewhat different.
If your transmitter is black wrinkle painted and
has a big RF choke next to the tank coil, it's
AN/ARC-5. If it's black and has not such coil,
but has an anchor in yellow paint on the back skirt,
it's an ATA. If it's silver, it's a later SCR-274N.
If it's black, has no RF Choke and has a "BC-4xx"
number on the back skirt, it's SCR-274N.

Transmitter Plug Pin-out:
(Note: If yours has an octal socket or anything
other then the 7-pin Mica connector,
then it's a modification and all bets are off.)

For AN/ARC-5-
There are seven pins. The pin in the center is
pin #7. Locate the pin that is grounded
to the chassis. This is pin #4.
Count the others *clockwise* around accordingly.

1. No Connection
2. +200VDC for the Osc. (needs to be right for stability).
3. Keying Relay (ground to key).
4. Ground.
5. A+ 24-28 VDC.
6. PA Screen Voltage (use 20K 5W dropping res. from B+).
7. PA Plate B+ Voltage +550VDC

For ATA/ARA and SCR-274N:
There are seven pins.
The pin in the center is pin #7.
Locate the pin that is grounded
to the chassis. This is pin #1.
Count the others *clockwise* around accordingly.

1. Ground
2. Test point for PA grid current.
3. +200VDC for the Osc. (needs to be right for stability).
4. PA Screen Voltage (use 20K 5W dropping res. from B+).
5. Keying Relay (ground to key).
6. A+ 24 VDC.
7. PA Plate B+ Voltage +550VDC.

The best way to get power to the rig is the way the
original engineers intended. I don't mean a dynamotor-
I mean a good, solid 550 VDC source and a divider.
Both the AN/ARC-5 and SCR-274N units derive their voltages
using a voltage divider network. We'll draw a divider that
matches the one used in the original power supply.
I very much recommend it.

Primary power should be 24-28 VDC at about 2.5 amps for relay
and filiments and B+ of 500-600 VDC at about 200 MA.
We will assume the designer's specs of
550 VDC B+ and 26 VDC filiment.
Get a pencil and a piece of paper. Follow along:

Place a dot on your paper and call that point "A".

Draw a line right to point "B".
From point "B", draw a line down and

connect a 20 K-ohm, 5 watt resistor here.
Call the other end of this resistor point "C".

Draw a line right from point "B" to point "D".

From "D", draw a line downward
and connect a 15 K-ohm, 10 watt resistor.
Call the other end of this resistor point "E".

From point "E", connect a 100 K-ohm 1 watt resistor to ground.

Draw a line right from point "D" to point "F".
Draw a line right from point "E" to point "H".

+550 VDC in at point "A".
+550 VDC out to PA plates at point "F".
+270 VDC out to PA screens at point "C".
+200 VDC out to Oscillator at point "H".

Bypass all outputs with about .01 ufd to ground.

If you wish to regulate the screens for AM,
connect an 0D3 VR tube with a .5 ufd at 300VDC
cap across it between point "C" and ground.
This will bring the screen down to 150 volts.

If you use this network, and use correct antenna
matching, you will be able to properly load and
tune your command set transmitter to rated output.

Voltages lower then 550 VDC will work just fine
with the same network. Voltages much higher will
cause MO drift and increase chirp.

GL OM DE Dave AB5S