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TR-4C transmit
All,
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I recently picked up a TR-4C and power supply. I rebuilt the PS and was able to get the TR-4C cleaned up and working properly. I know this is a SSB rig but also has a CW option. I have good output around 200 watts. I see myself on the RBN site. The problem is that no one answers my CQ or when I respond to a CQ I never get an answer.
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Yesterday I found a POTA station on a known frequency, say 14.050? I tuned into a SDR in Virginia and I could hear my transmission. The transmission was at 14.0493 I repeated this trial several time and my transmit is always lower that the receive frequency.
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That explains why I don't get a response. So what is the fix or workaround. This rig has great reception so there has to be something I am missing.
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Dean/ N2TNN |
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Re: T-4XC Final Cathode Resistors
I have an extensive collection of parts that I¡¯ve owned, off and on, since the 1980s (it¡¯s a long story). In this stockpile, I have lots of resistors, including some carbon comps that go back as far as 70 years old.? Most but not all of the CC resistors have drifted out of tolerance and I have enough good ones to throw them out as I go through them.? I¡¯m curious, though, if I could get them back into tolerance by baking them. It¡¯s easy enough to do and I¡¯ve heard hearsay that it could work but have any of you tried it? I¡¯m more interested in trying this with 1 W and larger resistors. I have more than enough 1/2 W and smaller.? 73, Steve Wedge, W1ES Time flies like an arrow. Fruit flies like a banana. Sent from for iOS On Sun, Feb 9, 2025 at 00:41, Jim VE7RF via groups.io <jim.thom@...> wrote:
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Re: Drake TR-7 - Noisy transmitter
Jim,
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Thanks for the clarification. What you described (better) is what I took away from reading the Drake manual. The process was so quirky, it raised a flag in my head. Poking screwdrivers through connectors and shorting stuff out, indeed!
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I used an Audacity session running on the PC and got it to generate an 800 Hz tone, which I zero-beated to. Near enough!
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Regards,
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Mark, G4FPH.
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Re: T-4XC Final Cathode Resistors
In the T-4XC I worked on there's a separate 3.3ohm resistor for the current metering.
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Thanks for the info. on resistors; early in my working life ( mil comms) it was drilled into me that carbon film ones were fragile and to be avoided so I've always stuck with MOF and never questioned it. Always something new to learn.
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73, Steve G8GSQ |
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Re: AC-4 Power Supply 10K Bias Trimmer Replacement
You can find about of the same make and size and move the insides to the old enclosure.? I have done this with several different pots.? Steve Wedge, W1ES Time flies like an arrow. Fruit flies like a banana. Sent from for iOS On Sat, Feb 8, 2025 at 20:07, Joe W7BWA via groups.io <W7BWA@...> wrote:
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Re: AC-4 Power Supply 10K Bias Trimmer Replacement
¿ªÔÆÌåÓýA bit late to this thread.? Drake seem to use a lot of the CTS 450 series pots.? I would guess the pot in the AC4 is a CTS 450 series.? You could get one of these from Mouser and swap out the wafer.? ??? Just be careful not to break any of the tabs securing the wafer when you take the pots apart, replace the wafer on the short shaft pot and put it back together.73 Stan KM4HQE On 2/8/25 19:07, Joe W7BWA via
groups.io wrote:
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Re: Changes/alterations in early (S/N~18,300) R-4C IF
Kinda nice how spell-checker changes ¡°pentagrid¡± to ¡°pentagram¡±!
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Gary W0DVN On Feb 8, 2025, at 5:08?PM, Jim Shorney via groups.io <jimNU0C@...> wrote: |
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Re: Changes/alterations in early (S/N~18,300) R-4C IF
Gary, try putting the original screen resistor back and swap out tubes. It sounds like someone was chasing their tail over a gassy tube.? Steve Wedge, W1ES Time flies like an arrow. Fruit flies like a banana. Sent from for iOS On Sat, Feb 8, 2025 at 17:00, Gary Follett via groups.io <xntrick1948@...> wrote:
I am helping a fellow with his dead R-4C. I found the original problem, a puncture in one of the coax cables' |
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Good audio - T4XC and R4C
On 12m this morning, I received a good SSB audio report from MN.? I've had other good SSB audio reports.? I'm using a Shure 444.? My CW and SSB reception sound great as well.. maybe better sounding than my K4?? ? Could it be that the absence of SRD,digitization, (etc)? and the presence of RF engineers on the T4XC/R4C design team were contributors?? 50-year-old radios.? Very cool. 73 Jay W6CJ |
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Changes/alterations in early (S/N~18,300) R-4C IF
I am helping a fellow with his dead R-4C. I found the original problem, a puncture in one of the coax cables'
insulation pressing against the 12 volt line, pulling it to ground. Fortunately, this radio had been updated to a 7812 voltage regulator, which self-limited preventing its destruction. However, someone had made other changes, among them the addition of a potentiometer in place of the 820 Ohm series resistor in the S meter zero circuit. It was poorly done and the pot was dangling in the air. I tried to revert back to schematic original, by putting in the 820 ohm fixed resistor where it belongs, but now I cannot zero the S meter. I determined a few things. First, there was a 6BE6 in place of V5 (6BA6). Replacing this with a known-good 6BA6 improved the zero but not completely. I then determined that the screen resistor on V2 (6HS6) had been changed from 100K to 10K. This causes this end of the S meter bridge to draw too much current in a no-signal condition and this is the reason for the offset in the S meter (~S8). Now I could just kludge in the pot again, but do a better job. I know it will zero with this change. I would like to know, first, if there is a good driving reason for there to be a change in the screen resistor value for V2 and also for the use of a pentagram converter tube (6BE6) in place of the pentode amplifier 6BA6 at V5. Bob probably knows¡ Gary W0DVN |
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T-4XC Bandswitch positions
T-4XC Band switch waver positions? On the T-4XC I purchased, the waver band switch is in the wrong positions. crystal positions are fixed, the others may be wrong too! After tuning only a small display on the meter. Can someone help me and take photos of all waver positions, for example for 40m. hm ?. . .? |
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Re: T-4XC Final Cathode Resistors
One watt is enough. Modern carbon film will do fine, they do not drift. Metal film will also do fine. I think Garry used to recommend oxide coated film. Since the drop is part of the measurement of "plate" current (actually cathode current) the value is of some importance.
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Old fashioned carbon composition resistors were never better than 5% because the heat of soldering them could cause that much drift. On 2/8/2025 6:24 AM, Craig W8CS via groups.io wrote:
After updating my AC-4, I fired up the T-4XC and am dealing with all of the little usual issues after being dormant for a quarter century. --
Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
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Re: T-4XC Final Cathode Resistors
Carbon film will run at red heat without damage. I spent some of my wasted youth working for a resistor manufacturer. We made established reliability metal film and mil spec carbon film resistors.
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Otherwise I agree. There are oxide coated composition resistors which work well for this sort of application. There are very few virtues to old type carbon composition resistors. They were very widely used for a couple of generations because they were cheap to make. Laser trimming of carbon and metal film has reduced production costs to the point where they are now quite cheap. On 2/8/2025 9:58 AM, Steve G8GSQ via groups.io wrote:
In general I'd say use metal film for everything. In this case, maybe consider carbon film and don't overdo the power rating. If the resistor burns out it might just save the tube; metal film can usually take a lot of overload. --
Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
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Re: T-4XC Final Cathode Resistors
In general I'd say use metal film for everything. In this case, maybe consider carbon film and don't overdo the power rating. If the resistor burns out it might just save the tube; metal film can usually take a lot of overload.
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The T4 I've just been working on had run just fine for years with 18ohm (2W metal film) resistors until operator error took them and the tubes out.
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I think the exact value isn't critical. 2 x 33R 0.5W is a simple option.
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Steve G8GSQ |
Jim Shorney
Jay W6CJ
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