"R. Ton" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Thanks to all (!!) -- more coming when I get a chance (life is getting in the way of fun right now).
So far, I've had the chance to change out the relay -- the ONE spare part I had on hand. No difference. The rig does go into transmit when switched to CW mode (no key plugged in). Both relays respond and the receiver mutes. I just noticed this AM that the .025 plate current reading I get is there even with the power off. Meter moves about a needle's width when put into transmit and the S-meter reads about 7-8 in transmit -- may be another clue? And thanks for the hollow-state theory Garey. It's been a REALLY long time since I've worked on any tube gear, but it's slowly coming back to me. :) I'll be digging some more in a bit here and will report back. I'll also see if I can catch the technical net this afternoon. 7.238 @ 2000Z, right? Thanks again everyone! 73, Rob (KFØRT) > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Garey Barrell > Sent: Sunday, April 16, 2006 8:41 AM > To: Drakelist > Subject: Re: [drakelist] TR-4C transmitter troubleshooting > > > > Garey Barrell <[EMAIL PROTECTED]> made an utterance to the > drakelist gang > ---------------------------------------------------------------------- > Hi Kevin - > > Expertise is just experience clouded by memory! :-) > > I don't think I've ever come across a PAIR of finals that "lit up", but > wouldn't draw at least a couple hundred mA if they had the DC potentials > applied to them. In fact, I can only remember one tube that was "open", > but lit. I still think it had a broken weld inside it!! :-) > > But then I've been wrong before. A favorite med school phrase, "when > you hear hoof beats, think horses, not zebras" comes to mind! > > Hopefully Rob will get it fixed in spite of my help and let us know the > truth!! > > 73, Garey - K4OAH > Atlanta > > Drake B & C-Line Service CDs > <http://www.k4oah.com> > > > > kbgluxford wrote: > > > > kbgluxford <[EMAIL PROTECTED]> made an utterance to the drakelist > > gang > > ---------------------------------------------------------------------- > > I certainly don't have Garey's expertise or long experience, but I did > > have a similar problem on one of my TX4 transmitters recently. I > > changed out the PA tubes and the problem disappeared. > > > > 73 > > Kevin > > VK3DAP / ZL2DAP > > > > Garey Barrell wrote: > >> > >> 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 > ---------------------------------------------------------------------- > ---------------------------------------------------------------------- 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 ----------------------------------------------------------------------
