I was hoping this might be the case... thanks Gary your help and comments are very much appreciated. Michael - NZ4D
On Mon, Jan 23, 2012 at 10:16 PM, Garey Barrell <[email protected]> wrote: > Michael - > > The open circuit voltage is about -65, and the current is less than a mA. > No need for any protection. > > If you're feeling adventurous, you can lick your finger and key the > transceiver by putting it across the key. > > The TO was around when many (most?) transmitters were cathode keyed, with > hundreds of volts and full PA current! > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line > and TR-4/C Service Supplement CDs > <www.k4oah.com> > > > > Michael A. Kelly wrote: >> >> Howdy everyone, >> >> I have a Hallicrafter's TO Keyer that I am using with a TR-4CW. >> According to the Hallicrafters manual there is a section that reads: >> >> "The mercury-wetted relay contact rating is 5 amperes maximum, or 500 >> volts maximum, the product not to exceed 250 volt-amperes with contact >> protection. For example, the maximum allowable voltage with a >> 5-ampere load is 50 volts (5A X 50 V =250 VA); the maximum allowable >> current with a 500-volt supply is 0.5 ampere (500V x 0.5A = 250 VA). >> >> Except for very light loads (under 2 MA and 50 V), the relay must be >> provided with a contact protection network consisting of a capacitor >> and resistor in series. The network prevents possible arcing which >> would eventually destroy the contacts." >> >> Anyone want to venture what the approximate current load would/should >> be when the rig is keyed, or what is the open circuit load voltage at >> the keying points? >> >> They give the example using the chart after measuring the voltage at >> 150V and the current at 50 MA would generate needing a protection >> network consisting of a 0.001 uF capacitor (limiting capacity) in >> series with a 750 ohm resistor. >> >> Surely folks have already done the checking using a TO Keyer with a >> TR-4anything and can tell me what is a good guess for capacitance and >> resistance needed? >> >> Thanks, >> >> Michael NZ4D >> > _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
