RE: [drakelist] TR-4C transmitter troubleshooting
R. Ton [EMAIL PROTECTED] made an utterance to the drakelist gang -- Hi Garey- Well, maybe wrapping up this chapter in the TR-4C saga. I received a matched set of Sylvania NOS finals today (these are from a private party and NOT the tubes I ordered from Antique). Plugged them in, and we're cookin' now. Bias set up per book just fine and after tuning the old gal up, I'm showing a little over 200 watts into a dummy load on my cheap and cheesy MFJ wattmeter on 20 meters. Plate meter on the rig indicating about 520ma. Anyway, wanted to thank everyone here for the help! I learned a bit and had some fun in the process. I'll no doubt be back. In fact, I'll report back when I get the set of tubes from Antique. Time for some fun... :) Many thanks, again. 73, Rob (KFØRT) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Garey Barrell Sent: Sunday, April 16, 2006 9:09 PM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang -- Rob - Certainly looks like tubes Have you tried turning down the bias (towards 0 volts)? I can't think of anything else to try. Let us know what happens! 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 -- Garey- It's sure looking like the tubes, odd as that seems. Here are the readings I'm getting (measured at the tube socket): Pin 1 - 255VDC RX, 247VDC TX Pin 2 - -58 VDC Pin 3 - 155VDC RX, 0VDC TX Pin 4, 5 - Filaments (good - tubes light, get hot, RX works) Pin 6 - -58 VDC (Same as pin 2) Pin 7 - 255VDC RX, 247VDC TX (Same as pin 1) Pin 8 - Ground Plate cap - 748VDC (+/- 1VDC, all 3) Definately agree that all three tubes would have to be open to draw no current, but there doesn't seem to be another explanation. It sure seems odd. Almost impossible, even. You would think that opening the meter shunt resistor would actually protect the tubes -- they were obviously drawing plenty of current when the resistor blew. Not knowing the history of this rig though, it's hard to say. I pulled the tubes -- nothing obvious to be seen there. The above readings were taken after I put the tubes back in. Wish like heck I had a spare set to try, but I now have a set on order. (BTW -- I've never dealt with Antique Electronic Supply - tubesandmore.com before, but if anyone's interested, they have 6JB6A's on 'sale' for $14.60 apiece until 5/14 and claim they'll match them for $1.25 apiece.) A tube sale??? So... unless someone sees something wierd with the voltage readings, I guess I'm waiting on tubes. Oh... also checked the meter switch on the load control -- it ohms out fine. The factory selected resistor (R13) in this rig is 39 ohms. Many thanks again! 73, Rob (KFØRT) -Original Message- From: Garey Barrell [mailto:[EMAIL PROTECTED] Sent: Sunday, April 16, 2006 4:45 PM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Rob - I find it hard to believe that ALL three tubes are totally dead, assuming the filaments are lit! First, have you measured the screen voltage on the tubes? Each tube should have about 250VDC on the screen pin via a 68 ohm, 1W resistor. Where are you measuring the plate voltage? Measure at the plate cap of each tube. Again, if there is 750 VDC on the plate cap, 250 VDC on the screen, 0 VDC on the grid and 0 VDC at the cathode, each one of those tubes would draw over an amp of cathode current. To control this current, you apply a negative voltage to the grid, and typically ~ -55 VDC should limit that current to ~ 30 mA. IF these conditions are met at the tube pins, then the only remaining answer is three completely open tubes, which I still find hard to comprehend. The three tubes are in parallel, so if any one of them is even slightly good, you should see plate current! If the cathode PINS are at 0 VDC in transmit, then the RFC, meter shunt and relay contact are OK. There are two RF chokes in series between the HV feedthrough under the chassis and the plate caps of all three tubes. 73, Garey - K4OAH Atlanta Drake B C-Line Service CDs http://www.k4oah.com R. Ton wrote: Great idea, Garey... With my meter set as low as it'll go, I'm showing about 0.3 mV across the shunt resistor in transmit. This thing isn't drawing any current at all! In receive, I'm getting a cathode voltage of about 155V and a plate voltage of about 754V. The 754V plate
RE: [drakelist] TR-4C transmitter troubleshooting
R. Ton [EMAIL PROTECTED] made an utterance to the drakelist gang -- Alan, Not much. It swings from 255V in receive to 247V transmit. I should have some NOS tubes on Thursday, so will know more then. Thanks! 73, Rob (KFØRT) -Original Message- From: ALAN CHANDLER [mailto:[EMAIL PROTECTED] Sent: Monday, April 17, 2006 6:56 PM To: R. Ton Subject: Re: [drakelist] TR-4C transmitter troubleshooting Rob, Does the grid 1 voltage change when you go from receive to transmit? Alan - Original Message - From: R. Ton [EMAIL PROTECTED] To: ALAN CHANDLER [EMAIL PROTECTED] Sent: Sunday, April 16, 2006 5:58 PM Subject: RE: [drakelist] TR-4C transmitter troubleshooting Hi Alan, Thanks for the message. It looks like I can adjust the AC-4's bias output from -43 to -76 volts. The schematic shows -60. I'm not seeing any cathode current anywhere within the bias range of the supply. Pretty strange... 73, Rob (KFØRT) -Original Message- From: ALAN CHANDLER [mailto:[EMAIL PROTECTED] Sent: Sunday, April 16, 2006 6:45 PM To: R. Ton Subject: Re: [drakelist] TR-4C transmitter troubleshooting Hi Rob, Is the grid 1 voltage at -58 in transmit. This sounds negative enough to bias the tubes past cutoff, i.e. no current. Has the bias pot in the power supply been adjusted? Most of the tubes that I remember need around -35 volts to draw the proper idle current. 73, Alan - K6RFK - Original Message - From: R. Ton [EMAIL PROTECTED] To: [EMAIL PROTECTED] Cc: Drakelist drakelist@www.zerobeat.net Sent: Sunday, April 16, 2006 5:05 PM Subject: RE: [drakelist] TR-4C transmitter troubleshooting R. Ton [EMAIL PROTECTED] made an utterance to the drakelist gang -- Garey- It's sure looking like the tubes, odd as that seems. Here are the readings I'm getting (measured at the tube socket): Pin 1 - 255VDC RX, 247VDC TX Pin 2 - -58 VDC Pin 3 - 155VDC RX, 0VDC TX Pin 4, 5 - Filaments (good - tubes light, get hot, RX works) Pin 6 - -58 VDC (Same as pin 2) Pin 7 - 255VDC RX, 247VDC TX (Same as pin 1) Pin 8 - Ground Plate cap - 748VDC (+/- 1VDC, all 3) Definately agree that all three tubes would have to be open to draw no current, but there doesn't seem to be another explanation. It sure seems odd. Almost impossible, even. You would think that opening the meter shunt resistor would actually protect the tubes -- they were obviously drawing plenty of current when the resistor blew. Not knowing the history of this rig though, it's hard to say. I pulled the tubes -- nothing obvious to be seen there. The above readings were taken after I put the tubes back in. Wish like heck I had a spare set to try, but I now have a set on order. (BTW -- I've never dealt with Antique Electronic Supply - tubesandmore.com before, but if anyone's interested, they have 6JB6A's on 'sale' for $14.60 apiece until 5/14 and claim they'll match them for $1.25 apiece.) A tube sale??? So... unless someone sees something wierd with the voltage readings, I guess I'm waiting on tubes. Oh... also checked the meter switch on the load control -- it ohms out fine. The factory selected resistor (R13) in this rig is 39 ohms. Many thanks again! 73, Rob (KFØRT) -Original Message- From: Garey Barrell [mailto:[EMAIL PROTECTED] Sent: Sunday, April 16, 2006 4:45 PM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Rob - I find it hard to believe that ALL three tubes are totally dead, assuming the filaments are lit! First, have you measured the screen voltage on the tubes? Each tube should have about 250VDC on the screen pin via a 68 ohm, 1W resistor. Where are you measuring the plate voltage? Measure at the plate cap of each tube. Again, if there is 750 VDC on the plate cap, 250 VDC on the screen, 0 VDC on the grid and 0 VDC at the cathode, each one of those tubes would draw over an amp of cathode current. To control this current, you apply a negative voltage to the grid, and typically ~ -55 VDC should limit that current to ~ 30 mA. IF these conditions are met at the tube pins, then the only remaining answer is three completely open tubes, which I still find hard to comprehend. The three tubes are in parallel, so if any one of them is even slightly good, you should see plate current! If the cathode PINS are at 0 VDC in transmit, then the RFC, meter shunt and relay contact are OK. There are two RF
RE: [drakelist] TR-4C transmitter troubleshooting
[EMAIL PROTECTED] made an utterance to the drakelist gang -- For what it's worth, I had lightning blow out 3 6JB6 tubes one time in a TR-4. I does happen. Lee w0vt Definately agree that all three tubes would have to be open to draw no current, but there doesn't seem to be another explanation. It sure seems odd. Almost impossible, even. You would think that opening the meter shunt resistor would actually protect the tubes -- they were obviously drawing plenty of current when the resistor blew. Not knowing the history of this rig th -- 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 --
Re: [drakelist] TR-4C transmitter troubleshooting
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 -- -- 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 --
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 --
RE: [drakelist] TR-4C transmitter troubleshooting
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
Re: [drakelist] TR-4C transmitter troubleshooting
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang -- Rob - OK, a little more information. When the 2 ohm meter shunt resistor opens up, the Final cathode current is routed through a slide switch mounted up on the LOAD capacitor shaft, (activated by pushing in the LOAD control,) a series resistor that is selected at test, (mounted on the slide switch terminals,) of typically ~200 ohms, and the plate meter. It wouldn't take much current to damage that resistor and/or meter with the shunt resistor open. Or if the slide switch contacts are not closing properly in the out position of the LOAD control. Perhaps your finals are drawing idle current, it's just not showing on the meter!? Measure the voltage drop across the meter shunt resistor. 100 mA should read 200 mV. By the way, if you're not used to working on tube gear, keep in mind that 650V (OR 250v) BITES! An AC-4 bleeds down pretty quickly when turned off, but only your meter knows for sure before you stick your fingers in there! 73, Garey - K4OAH Atlanta Drake B C-Line Service CDs http://www.k4oah.com R. Ton wrote: 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
RE: [drakelist] TR-4C transmitter troubleshooting
R. Ton [EMAIL PROTECTED] made an utterance to the drakelist gang -- Great idea, Garey... With my meter set as low as it'll go, I'm showing about 0.3 mV across the shunt resistor in transmit. This thing isn't drawing any current at all! In receive, I'm getting a cathode voltage of about 155V and a plate voltage of about 754V. The 754V plate reading is the same as my AC-4 under no load. In transmit, there is no change in plate voltage, but the cathode voltage goes to zero. According to the schematic, the cathodes are grounded via the T/R relay, the 2 ohm shunt resistor, an RF choke and a 15 ohm resistor (one 15 ohm resistor for each tube). Even through the 15 ohm resistor, I'm showing 0V on the cathode in transmit. Wierd. This would sure seem to indicate that the finals aren't conducting at all. Still, very weak on my tube theory here -- could a grid condition cause this? I'm showing a good -60V on pins 2 and 6. I was also thinking that a 1 watt, 2 ohm resistor should be able to handle about 700ma without cooking. When I got the rig, this resistor was burned in half. Maybe it's time to pull the tubes and see if anything is rattling around inside? :( Is my thinking halfway straight? :) Hoping like heck the plate current meter isn't shot -- I have a feeling those are hard to get. Thanks again everyone! 73, Rob (KFØRT) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Garey Barrell Sent: Sunday, April 16, 2006 9:57 AM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang -- Rob - OK, a little more information. When the 2 ohm meter shunt resistor opens up, the Final cathode current is routed through a slide switch mounted up on the LOAD capacitor shaft, (activated by pushing in the LOAD control,) a series resistor that is selected at test, (mounted on the slide switch terminals,) of typically ~200 ohms, and the plate meter. It wouldn't take much current to damage that resistor and/or meter with the shunt resistor open. Or if the slide switch contacts are not closing properly in the out position of the LOAD control. Perhaps your finals are drawing idle current, it's just not showing on the meter!? Measure the voltage drop across the meter shunt resistor. 100 mA should read 200 mV. By the way, if you're not used to working on tube gear, keep in mind that 650V (OR 250v) BITES! An AC-4 bleeds down pretty quickly when turned off, but only your meter knows for sure before you stick your fingers in there! 73, Garey - K4OAH Atlanta Drake B C-Line Service CDs http://www.k4oah.com R. Ton wrote: 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
RE: [drakelist] TR-4C transmitter troubleshooting
R. Ton [EMAIL PROTECTED] made an utterance to the drakelist gang -- Looks like it's good, Mark. I sprayed it with Deoxit when I did the other contacts and it ohms out good. 73, Rob (KFØRT) -Original Message- From: MNACE [mailto:[EMAIL PROTECTED] Sent: Sunday, April 16, 2006 5:17 PM To: R. Ton; [EMAIL PROTECTED] Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting I had a TR4-C that had a very dirty slide switch that Garey talks about (the one that switches between plate current and power out). I actually (very very carefully) took it apart, cleaned the contacts, re-assembled, sprayed with deoxit, and all the meter problems went away. The other option would be to replace with a new slide switch 73, Mark N5KAE - Original Message - From: R. Ton [EMAIL PROTECTED] To: [EMAIL PROTECTED] Cc: Drakelist drakelist@www.zerobeat.net Sent: Sunday, April 16, 2006 4:14 PM Subject: RE: [drakelist] TR-4C transmitter troubleshooting R. Ton [EMAIL PROTECTED] made an utterance to the drakelist gang -- Great idea, Garey... With my meter set as low as it'll go, I'm showing about 0.3 mV across the shunt resistor in transmit. This thing isn't drawing any current at all! In receive, I'm getting a cathode voltage of about 155V and a plate voltage of about 754V. The 754V plate reading is the same as my AC-4 under no load. In transmit, there is no change in plate voltage, but the cathode voltage goes to zero. According to the schematic, the cathodes are grounded via the T/R relay, the 2 ohm shunt resistor, an RF choke and a 15 ohm resistor (one 15 ohm resistor for each tube). Even through the 15 ohm resistor, I'm showing 0V on the cathode in transmit. Wierd. This would sure seem to indicate that the finals aren't conducting at all. Still, very weak on my tube theory here -- could a grid condition cause this? I'm showing a good -60V on pins 2 and 6. I was also thinking that a 1 watt, 2 ohm resistor should be able to handle about 700ma without cooking. When I got the rig, this resistor was burned in half. Maybe it's time to pull the tubes and see if anything is rattling around inside? :( Is my thinking halfway straight? :) Hoping like heck the plate current meter isn't shot -- I have a feeling those are hard to get. Thanks again everyone! 73, Rob (KFØRT) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Garey Barrell Sent: Sunday, April 16, 2006 9:57 AM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang -- Rob - OK, a little more information. When the 2 ohm meter shunt resistor opens up, the Final cathode current is routed through a slide switch mounted up on the LOAD capacitor shaft, (activated by pushing in the LOAD control,) a series resistor that is selected at test, (mounted on the slide switch terminals,) of typically ~200 ohms, and the plate meter. It wouldn't take much current to damage that resistor and/or meter with the shunt resistor open. Or if the slide switch contacts are not closing properly in the out position of the LOAD control. Perhaps your finals are drawing idle current, it's just not showing on the meter!? Measure the voltage drop across the meter shunt resistor. 100 mA should read 200 mV. By the way, if you're not used to working on tube gear, keep in mind that 650V (OR 250v) BITES! An AC-4 bleeds down pretty quickly when turned off, but only your meter knows for sure before you stick your fingers in there! 73, Garey - K4OAH Atlanta Drake B C-Line Service CDs http://www.k4oah.com R. Ton wrote: 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
RE: [drakelist] TR-4C transmitter troubleshooting
R. Ton [EMAIL PROTECTED] made an utterance to the drakelist gang -- Garey- It's sure looking like the tubes, odd as that seems. Here are the readings I'm getting (measured at the tube socket): Pin 1 - 255VDC RX, 247VDC TX Pin 2 - -58 VDC Pin 3 - 155VDC RX, 0VDC TX Pin 4, 5 - Filaments (good - tubes light, get hot, RX works) Pin 6 - -58 VDC (Same as pin 2) Pin 7 - 255VDC RX, 247VDC TX (Same as pin 1) Pin 8 - Ground Plate cap - 748VDC (+/- 1VDC, all 3) Definately agree that all three tubes would have to be open to draw no current, but there doesn't seem to be another explanation. It sure seems odd. Almost impossible, even. You would think that opening the meter shunt resistor would actually protect the tubes -- they were obviously drawing plenty of current when the resistor blew. Not knowing the history of this rig though, it's hard to say. I pulled the tubes -- nothing obvious to be seen there. The above readings were taken after I put the tubes back in. Wish like heck I had a spare set to try, but I now have a set on order. (BTW -- I've never dealt with Antique Electronic Supply - tubesandmore.com before, but if anyone's interested, they have 6JB6A's on 'sale' for $14.60 apiece until 5/14 and claim they'll match them for $1.25 apiece.) A tube sale??? So... unless someone sees something wierd with the voltage readings, I guess I'm waiting on tubes. Oh... also checked the meter switch on the load control -- it ohms out fine. The factory selected resistor (R13) in this rig is 39 ohms. Many thanks again! 73, Rob (KFØRT) -Original Message- From: Garey Barrell [mailto:[EMAIL PROTECTED] Sent: Sunday, April 16, 2006 4:45 PM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Rob - I find it hard to believe that ALL three tubes are totally dead, assuming the filaments are lit! First, have you measured the screen voltage on the tubes? Each tube should have about 250VDC on the screen pin via a 68 ohm, 1W resistor. Where are you measuring the plate voltage? Measure at the plate cap of each tube. Again, if there is 750 VDC on the plate cap, 250 VDC on the screen, 0 VDC on the grid and 0 VDC at the cathode, each one of those tubes would draw over an amp of cathode current. To control this current, you apply a negative voltage to the grid, and typically ~ -55 VDC should limit that current to ~ 30 mA. IF these conditions are met at the tube pins, then the only remaining answer is three completely open tubes, which I still find hard to comprehend. The three tubes are in parallel, so if any one of them is even slightly good, you should see plate current! If the cathode PINS are at 0 VDC in transmit, then the RFC, meter shunt and relay contact are OK. There are two RF chokes in series between the HV feedthrough under the chassis and the plate caps of all three tubes. 73, Garey - K4OAH Atlanta Drake B C-Line Service CDs http://www.k4oah.com R. Ton wrote: Great idea, Garey... With my meter set as low as it'll go, I'm showing about 0.3 mV across the shunt resistor in transmit. This thing isn't drawing any current at all! In receive, I'm getting a cathode voltage of about 155V and a plate voltage of about 754V. The 754V plate reading is the same as my AC-4 under no load. In transmit, there is no change in plate voltage, but the cathode voltage goes to zero. According to the schematic, the cathodes are grounded via the T/R relay, the 2 ohm shunt resistor, an RF choke and a 15 ohm resistor (one 15 ohm resistor for each tube). Even through the 15 ohm resistor, I'm showing 0V on the cathode in transmit. Wierd. This would sure seem to indicate that the finals aren't conducting at all. Still, very weak on my tube theory here -- could a grid condition cause this? I'm showing a good -60V on pins 2 and 6. I was also thinking that a 1 watt, 2 ohm resistor should be able to handle about 700ma without cooking. When I got the rig, this resistor was burned in half. Maybe it's time to pull the tubes and see if anything is rattling around inside? :( Is my thinking halfway straight? :) Hoping like heck the plate current meter isn't shot -- I have a feeling those are hard to get. Thanks again everyone! 73, Rob (KFØRT) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Garey Barrell Sent: Sunday, April 16, 2006 9:57 AM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang -- Rob - OK, a little more information. When the 2 ohm meter shunt resistor opens up, the Final cathode current is routed through a slide switch mounted up
Re: [drakelist] TR-4C transmitter troubleshooting
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang -- Rob - Certainly looks like tubes Have you tried turning down the bias (towards 0 volts)? I can't think of anything else to try. Let us know what happens! 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 -- Garey- It's sure looking like the tubes, odd as that seems. Here are the readings I'm getting (measured at the tube socket): Pin 1 - 255VDC RX, 247VDC TX Pin 2 - -58 VDC Pin 3 - 155VDC RX, 0VDC TX Pin 4, 5 - Filaments (good - tubes light, get hot, RX works) Pin 6 - -58 VDC (Same as pin 2) Pin 7 - 255VDC RX, 247VDC TX (Same as pin 1) Pin 8 - Ground Plate cap - 748VDC (+/- 1VDC, all 3) Definately agree that all three tubes would have to be open to draw no current, but there doesn't seem to be another explanation. It sure seems odd. Almost impossible, even. You would think that opening the meter shunt resistor would actually protect the tubes -- they were obviously drawing plenty of current when the resistor blew. Not knowing the history of this rig though, it's hard to say. I pulled the tubes -- nothing obvious to be seen there. The above readings were taken after I put the tubes back in. Wish like heck I had a spare set to try, but I now have a set on order. (BTW -- I've never dealt with Antique Electronic Supply - tubesandmore.com before, but if anyone's interested, they have 6JB6A's on 'sale' for $14.60 apiece until 5/14 and claim they'll match them for $1.25 apiece.) A tube sale??? So... unless someone sees something wierd with the voltage readings, I guess I'm waiting on tubes. Oh... also checked the meter switch on the load control -- it ohms out fine. The factory selected resistor (R13) in this rig is 39 ohms. Many thanks again! 73, Rob (KFØRT) -Original Message- From: Garey Barrell [mailto:[EMAIL PROTECTED] Sent: Sunday, April 16, 2006 4:45 PM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Rob - I find it hard to believe that ALL three tubes are totally dead, assuming the filaments are lit! First, have you measured the screen voltage on the tubes? Each tube should have about 250VDC on the screen pin via a 68 ohm, 1W resistor. Where are you measuring the plate voltage? Measure at the plate cap of each tube. Again, if there is 750 VDC on the plate cap, 250 VDC on the screen, 0 VDC on the grid and 0 VDC at the cathode, each one of those tubes would draw over an amp of cathode current. To control this current, you apply a negative voltage to the grid, and typically ~ -55 VDC should limit that current to ~ 30 mA. IF these conditions are met at the tube pins, then the only remaining answer is three completely open tubes, which I still find hard to comprehend. The three tubes are in parallel, so if any one of them is even slightly good, you should see plate current! If the cathode PINS are at 0 VDC in transmit, then the RFC, meter shunt and relay contact are OK. There are two RF chokes in series between the HV feedthrough under the chassis and the plate caps of all three tubes. 73, Garey - K4OAH Atlanta Drake B C-Line Service CDs http://www.k4oah.com R. Ton wrote: Great idea, Garey... With my meter set as low as it'll go, I'm showing about 0.3 mV across the shunt resistor in transmit. This thing isn't drawing any current at all! In receive, I'm getting a cathode voltage of about 155V and a plate voltage of about 754V. The 754V plate reading is the same as my AC-4 under no load. In transmit, there is no change in plate voltage, but the cathode voltage goes to zero. According to the schematic, the cathodes are grounded via the T/R relay, the 2 ohm shunt resistor, an RF choke and a 15 ohm resistor (one 15 ohm resistor for each tube). Even through the 15 ohm resistor, I'm showing 0V on the cathode in transmit. Wierd. This would sure seem to indicate that the finals aren't conducting at all. Still, very weak on my tube theory here -- could a grid condition cause this? I'm showing a good -60V on pins 2 and 6. I was also thinking that a 1 watt, 2 ohm resistor should be able to handle about 700ma without cooking. When I got the rig, this resistor was burned in half. Maybe it's time to pull the tubes and see if anything is rattling around inside? :( Is my thinking halfway straight? :) Hoping like heck the plate current meter isn't shot -- I have a feeling those are hard to get. Thanks again everyone! 73, Rob (KFØRT) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Garey Barrell Sent: Sunday, April 16, 2006 9:57 AM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Garey
Re: [drakelist] TR-4C transmitter troubleshooting
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang -- Rob - Certainly looks like tubes Have you tried turning down the bias (towards 0 volts)? I can't think of anything else to try. Let us know what happens! 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 -- Garey- It's sure looking like the tubes, odd as that seems. Here are the readings I'm getting (measured at the tube socket): Pin 1 - 255VDC RX, 247VDC TX Pin 2 - -58 VDC Pin 3 - 155VDC RX, 0VDC TX Pin 4, 5 - Filaments (good - tubes light, get hot, RX works) Pin 6 - -58 VDC (Same as pin 2) Pin 7 - 255VDC RX, 247VDC TX (Same as pin 1) Pin 8 - Ground Plate cap - 748VDC (+/- 1VDC, all 3) Definately agree that all three tubes would have to be open to draw no current, but there doesn't seem to be another explanation. It sure seems odd. Almost impossible, even. You would think that opening the meter shunt resistor would actually protect the tubes -- they were obviously drawing plenty of current when the resistor blew. Not knowing the history of this rig though, it's hard to say. I pulled the tubes -- nothing obvious to be seen there. The above readings were taken after I put the tubes back in. Wish like heck I had a spare set to try, but I now have a set on order. (BTW -- I've never dealt with Antique Electronic Supply - tubesandmore.com before, but if anyone's interested, they have 6JB6A's on 'sale' for $14.60 apiece until 5/14 and claim they'll match them for $1.25 apiece.) A tube sale??? So... unless someone sees something wierd with the voltage readings, I guess I'm waiting on tubes. Oh... also checked the meter switch on the load control -- it ohms out fine. The factory selected resistor (R13) in this rig is 39 ohms. Many thanks again! 73, Rob (KFØRT) -Original Message- From: Garey Barrell [mailto:[EMAIL PROTECTED] Sent: Sunday, April 16, 2006 4:45 PM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Rob - I find it hard to believe that ALL three tubes are totally dead, assuming the filaments are lit! First, have you measured the screen voltage on the tubes? Each tube should have about 250VDC on the screen pin via a 68 ohm, 1W resistor. Where are you measuring the plate voltage? Measure at the plate cap of each tube. Again, if there is 750 VDC on the plate cap, 250 VDC on the screen, 0 VDC on the grid and 0 VDC at the cathode, each one of those tubes would draw over an amp of cathode current. To control this current, you apply a negative voltage to the grid, and typically ~ -55 VDC should limit that current to ~ 30 mA. IF these conditions are met at the tube pins, then the only remaining answer is three completely open tubes, which I still find hard to comprehend. The three tubes are in parallel, so if any one of them is even slightly good, you should see plate current! If the cathode PINS are at 0 VDC in transmit, then the RFC, meter shunt and relay contact are OK. There are two RF chokes in series between the HV feedthrough under the chassis and the plate caps of all three tubes. 73, Garey - K4OAH Atlanta Drake B C-Line Service CDs http://www.k4oah.com R. Ton wrote: Great idea, Garey... With my meter set as low as it'll go, I'm showing about 0.3 mV across the shunt resistor in transmit. This thing isn't drawing any current at all! In receive, I'm getting a cathode voltage of about 155V and a plate voltage of about 754V. The 754V plate reading is the same as my AC-4 under no load. In transmit, there is no change in plate voltage, but the cathode voltage goes to zero. According to the schematic, the cathodes are grounded via the T/R relay, the 2 ohm shunt resistor, an RF choke and a 15 ohm resistor (one 15 ohm resistor for each tube). Even through the 15 ohm resistor, I'm showing 0V on the cathode in transmit. Wierd. This would sure seem to indicate that the finals aren't conducting at all. Still, very weak on my tube theory here -- could a grid condition cause this? I'm showing a good -60V on pins 2 and 6. I was also thinking that a 1 watt, 2 ohm resistor should be able to handle about 700ma without cooking. When I got the rig, this resistor was burned in half. Maybe it's time to pull the tubes and see if anything is rattling around inside? :( Is my thinking halfway straight? :) Hoping like heck the plate current meter isn't shot -- I have a feeling those are hard to get. Thanks again everyone! 73, Rob (KFØRT) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Garey Barrell Sent: Sunday, April 16, 2006 9:57 AM To: R. Ton Cc: Drakelist Subject: Re: [drakelist] TR-4C transmitter troubleshooting Garey
[drakelist] TR-4C transmitter troubleshooting
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 --
Re: [drakelist] TR-4C transmitter troubleshooting
MNACE [EMAIL PROTECTED] made an utterance to the drakelist gang -- Have you replaced the T/R relay with a known good one? Mark N5KAE - Original Message - From: R. Ton [EMAIL PROTECTED] To: Drakelist drakelist@www.zerobeat.net Sent: Saturday, April 15, 2006 7:22 PM Subject: [drakelist] TR-4C transmitter troubleshooting 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 --
Re: [drakelist] TR-4C transmitter troubleshooting
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 --
