Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Rob -
You don't mention anything about "keying" the transmitter. You have to "key" the Push-To-Talk (PTT) of the microphone to switch it to transmit to see the idling plate current. You should hear the relay click when it closes.
If the final tubes have plate voltage, screen voltage and filament voltage, and the cathodes are returned to the negative pole of those supplies, they WILL draw plate current! The grid voltage is the only thing that keeps them from drawing AMPS of current in the presence of the other voltages.
There are two RF chokes in series between the +650VDC supply and the plate caps of the tubes. There is a 15 ohm, 1W resistor in series with each of the final tube cathodes to another RF choke, through the meter shunt resistor, and then through a relay contact to ground.
73, Garey - K4OAH Atlanta Drake B & C-Line Service CDs <http://www.k4oah.com> R. Ton wrote:
"R. Ton" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- I'm finally digging into a TR-4C I bought used some time ago. It "worked fine" when it was shipped here, but I haven't been able to get any power out of the transmitter. It at least oscillates -- I can hear it on a receiver in the same room. Starting at the beginning... The manual says to adjust the bias on the AC-4 so that the plate meter reads .1 amp. This is with the sideband switch counter-clockwise and the xmtr gain all the way down. The meter seems to read about .025 in receive and goes up just a little when the rig is switched to CW. Adjusting the bias has no effect on the plate meter, but it does indeed adjust the bias voltage. Setting it to -60 volts is no problem, but I'm unable to get any "real" plate current no matter what I do. Any ideas? I haven't done anything to the radio since I got it except spray the switches with Deoxit D5 and replace R45 (2 ohms -- plate meter shunt resistor!!). This resistor was fried in half. What am I in for? Many thanks in advance! 73, Rob (KFØRT) ---------------------------------------------------------------------- Submissions: drakelist@www.zerobeat.net Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ----------------------------------------------------------------------
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