I key my rigs in the primary, by way of low voltage relays. I use step start, a 110 volt timer relay bypasses a resistor after about 1/2 second. The resistor is picked to give about half plate voltage at the end of about 1/2 second.
I use many 12kv 1 amp diodes, two per power supply transformer tap, and even though I have a lot of capacitance in the power supplies, I never blew out a diode. The rigs all have protection circuits for screens and loss of bias. The grids have protection bias, plus grid leak bias. Screens always get an overload relay, manually reset, adjustable set point to just a little over normal current. I need protection circuits, brain burnout WILL have me trying to tune something up without an antenna selected, the exciter turned on, etc. I sometimes don't use the equipment for long periods, like summer, and/or I use one rig most, and would completely forget where to set things if I did not make a chart that mounts on the front panels. I also mark meter faces with grid current and so on, because after 6 months, I forget just what the grid current is supposed to be on a pair of 813 tubes, or 812 triodes. The charts include grid tuning positions for each band, plate tuning, loading, etc, so when I change bands, I can position things spot on before putting the power on. The meters and controls are labeled as what they are for, I would forget that also. Brett N2DTS > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Geoff/W5OMR > Sent: Tuesday, November 25, 2003 2:58 PM > To: [email protected] > Subject: [AMRadio] keying B+ > > > How do other people go about keying B+ in their rigs? > > What I do, as it was setup in my rig, back in 1986, > is that on the rear apron of the RF deck, is a tap for > bias voltage. When sufficient drive is applied, the > current from there to ground closes a contactor > relay that closes at about the same grid current > required by the 250TH's (45mA per, for a pair > for a total of 90mA - and I run around 125mA > to make sure the tubes are plenty cut-off for Class > C) and when drive is applied, the relay closes > and primary voltage (adjusted by a variac) is > applied to the plate transformers. > > What's another way? a relay to make/break the > center-tap to ground connection in the primary > of the plate transformers? > > 73 = Best Regards, > -Geoff/W5OMR > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio
