I can vouch for Mike's suggestion to series contacts. I used a DPDT with series contacts to create a HV SPDT and it worked well.
Dennis AE6C On Thu, Dec 10, 2009 at 1:02 PM, Al Parker <anc...@ec.rr.com> wrote: > 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 >
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