ART-13 Power Supply Confusion

[W7SOE]

I am building the cable from the PS to the Art-13.

Pin 9 is the positive side of the PA meter.

Pin 5 is ground

Pin 2 is the negative side of the PA meter

The low side of the HV power supply runs through a 13.4 ohm resistor.  Pin 2 connects to "low side" of the resistor (towards the xfmr) and pin 9 to the other side.

It looks like that side of the resistor (connected to pin 9) is also connected to ground, so the HV supply is connected to ground through the 13.4 ohm resistor. 

So pins 9 and 5 (ground) should be connected together.

Is it reasonable to connect these together in the connector?  (Plug U7)

Is this all correct?

Thanks

Rich

[W3RSW]

Don't have a schematic but this sounds similar to other military gear with an elevated ground in order to get a somewhat small bias voltage, e.g. the floating B- line in the BC 348 series, the multitapped resistor in many old receivers, such as Hammarlund SP200's etc.

Look at the pinouts and trace the wiring carefully and it may become apparent.

Anyone?

[WU2D]

Rich,

Yes, pins 5 and 9 tied together at the connector. Here is my guess - The drop across the resistor provides a few volts of protective bias for the 811's and it is part of the metering circuit. - 811's only work Class-B self bias at 1000 - 1250VDC, so the extra few volts of negative bias allows the unit to use 1500 VDC on the plates.

Can't ever have too many schematics, so here are more. 

Mike WU2D

[N2DTS]

I have run 811a,s at 1500 volts with no bias, does not seem to cause any problems, its not like the resting plate current is real high at 1500 volts, its only something like 10 ma higher.
Not sure why people worry about the bias...
More resting current gives less distortion, no?

Brett
N2DTS

[W7SOE]

I think I have it all worked out.  I have the cable to the ART-13 all built and installed, I may finish this yet...

Thanks all for the help.

BTW, I ran 811's modulating 813s in my old rig at over 1500V with no bias.....

Rich

[WU2D]

Rich,

811 class-B wives tales and ICAS stuff... Yes 811's can take whatever we throw. I actually am using the original dusty trusty Navy 811's in the transmitter when I got it. I bought 811A spares but never had to use them!

How is the supply coming along? Got 28VDC up?

And I have to admit that I never replaced my original connections to the side power pins with a real connector. I horseassed some jack sockets and heatshrink and strain relieved the whole mess and have not had to touch it since 1992. I was going to get around to finding a plug...

Mike WU2D

[KB2WIG]

Finding  the U7 (I think that it) is easy....

finding the ~ $50 is the hard part

beware your power supply connections


klc

[W7SOE]

Finding  the U7 (I think that it) is easy....

finding the ~ $50 is the hard part

beware your power supply connections


klc

Yes, that WAS a tough purchase....

Rich

[WA2TTP Steve]

I was lucky, my ART-13 came with the U7 connector with about a 2' cable coming out of it. I broke it out to a terminal strip and extended it about 12' to the power supply rack. Also had the remote control connector and box with it. Haven't hooked that up as yet. No need at this point.

I run my HV about 1200 volts. I'm nervious about going higher with the small mod iron. What do others run?

Steve
WA2TTP

[WU2D]

The small iron rule does not seem to apply with the "magic" transformer in the ART-13. I try not to go much above 1500V on AM or 2000V on CW.

Mike WU2D

[WA2TTP Steve]

Thanks Mike,

My supply tops out at about 2k, I'll make 1.5kv my high limit.

Steve