Hih Steve,
Mike had a good suggestion, here's another possibility that you could
try with what you've already got installed --
Put a bypass cap across the HV relay terminals, maybe a hefty one of 0.1
(@1kv or more), with a resistor in series with it (the cap), maybe 25 to 100
ohms. It depends a bit on the inductance that's in the HV ckt, you might
have to try a few values. Swamping the spike upon opening is the objective.
73
Al, W8UT
New Bern, NC
www.boatanchors.org
www.hammalund.info
----- Original Message -----
From: "Steve Berg" <wa9...@tbc.net>
To: "Mail List - Drake Gear Drake Gear" <drakelist@zerobeat.net>
Sent: Thursday, December 10, 2009 1:17 PM
Subject: Re: [Drakelist] AC4 Power Supply Modification
I may have asked this her before, but I thought I would post it anyway.
One of the oldest radios in my modest collection is a Gonset G-76
transceiver. I bought it used from AES in 1965, but was too poor as a
starving high school student to afford the companion power supply, so I
cobbled one together in breadboard fashion, and used it for years. But,
the voltages were never quite right. Now, Gonset power supplies are
virtually unobtainable, but I noted that the Drake power supplies had the
right voltages for my relic and bought one. I plan to get the Heathkit
Shoppe update for it. But, here is my dilemma. The G-76 requires that
the power supply disconnect the 650 volt DC line from the rig during
receive, and ground the line going to the radio. I used to use a surplus
ceramic 12 volt relay to do this, but that one has vanished somewhere in
the past 40+ years. I have tried to use normal power relays, but their
contacts are seemingly set up for breaking lower voltage DC, or are self
quenching when breaking AC. I have had some rather spectacular arcs in a
few relays when trying to use them for this application. Where might I
find a 12 volt AC coil power relay that will reliably open a 650 volt DC
circuit, and ground the far side that is going to the radio? Normally
this would be a simple SPDT relay.
Also, I want to make any modifications as reversible as possible as I do
not want to modify it so much that it would not be usable with a Drake rig
in the future.
Help?
Steve WA9JML
_______________________________________________
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist
_______________________________________________
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist
