Re: TR-4 Decreased Sensitivity on High Bands
Gary,
This morning, as I tuned up (into a dummy load) across all bands and I noticed that the XMTR GAIN seems to saturate at about the same point for all bands.? I seem to recall that a few weeks ago (before I started touching up the alignment points), I could get a LOT more gain out of the lower bands.
The only component work I've done is to replace the cap across the PA neutralizing cap and have that so I can minimize the spurious oscillations with the appropriate power peak at the valley (dip) of the plate tuning cap rotation.? I also replaced the cathode resistors with new 15R 1W metal film caps as the originals were out of spec and were not well-matched.
Maybe I've botched the alignment(s) and, perhaps, I need to revisit those.? Disappointing as I'd hoped to make things better and apparently that's not the case but I don't yet know what I might have done wrong (yes, I did use the designated dummy load when tweaking the injection couplers which I know is essential to getting those correct).
Thanks again,
Barry - N4BUQ
From: "Gary Follett via groups.io" <xntrick1948@...>
One test I have found to be useful is to plot output power on a given band versus position of the TX gain pot on the different bands. If you find that ?the saturation point of output (the point at which increasing the gain position produces no increase in output) versus position of the pot does not change as you go up in bands, then likely you have an alignment issue or a drive issue before the final mixer, because these earlier stages should produce more output than needed on the low bands to make up for poorer efficiency on the higher bands. In other words, you should be able to drive the heck out of the radio on 80 meters well before the saturation point of the TX gain pot.? Receiver gain issues track TX gain issues religiously. If TX gain is weak, receiver gain will be weak too. Gary W0DVN On Apr 28, 2025, at 7:44?PM, Ham Radio via groups.io <bernard.murphy@...> wrote:
Steve: I assume you meant AGC. ? I have a TR-4 that has the same issue. ? Fine on TX but low on RX. ? See attached file.
--
73, Bernie. VE3FWF
Real?radios glow in the dark
<TR-4-tubes-sensitivity.xls>
|
Re: R7 parent board pin out
Thanks....? I missed your answer about board compatibility. Sorry, I don't mean to be a pest.
Thanks for all your help.
73, Dan (W3DF)
One again, yes. The two boards are interchangeable. However as I have already stated you will want to change all the small electrolytics from the output of the TDA2002 to the output of the rectifier/voltage multiplier. See attached photo of mine. That is not a gray cap in the front left. It was the same color as the others before it saw several years of continuous service. While you are at it you might want to put a 10uF from pin 1 of the LM317 to ground. It is recommended on the data sheets to improve ripple rejection and I have learned over the years that it is wise to follow such recommendations.
You may want to consider running the R7 from external DC. It will take a lot of heat out of the box.
On Mon, 28 Apr 2025 23:38:24 -0400
"Daniel W3DF via " <danflan49=[email protected]> wrote:
> And a newer version power supply board.? My R7 has the older one.? Will the
> new one work in an older R7?
> I don't want to destroy anything by trying to use this newer PS board.
--
73
-Jim
NU0C
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DRAKE USERS NET 7.238 MHZ.
Evan, K9SQG was our NCS for the Sunday Users net. There were 22 people checking into the net, and the users were using the following radios:?
?
A line: ?1
B line: ?1
C line: ?3
TR-4: ?4
TR-5: ?1
TR-7: ?5
Others: ?7
?
Next week's NCS will be Ron, WB4HFN.?
?
73'S,
Mark, WB0IQK
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Re: TR-4 Decreased Sensitivity on High Bands
Both, actually.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Apr 28, 2025 at 22:32, n4buq < n4buq@...> wrote:
Which relay did you clean?
Barry - N4BUQ
The one I¡¯m working on goes intermittent all bands but 15 and 10 are both weak, transmit and receive.?
Cleaned the relay but long term that hasn¡¯t helped. Replaced 4 dodgy tubes.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Apr 28, 2025 at 20:44, Ham Radio via groups.io <
bernard.murphy@...> wrote:
Steve: I assume you meant AGC. ? I have a TR-4 that has the same issue. ? Fine on TX but low on RX. ? See attached file.
--
73, Bernie. VE3FWF
Real?radios glow in the dark
|
Re: R7 parent board pin out
One again, yes. The two boards are interchangeable. However as I have already stated you will want to change all the small electrolytics from the output of the TDA2002 to the output of the rectifier/voltage multiplier. See attached photo of mine. That is not a gray cap in the front left. It was the same color as the others before it saw several years of continuous service. While you are at it you might want to put a 10uF from pin 1 of the LM317 to ground. It is recommended on the data sheets to improve ripple rejection and I have learned over the years that it is wise to follow such recommendations. You may want to consider running the R7 from external DC. It will take a lot of heat out of the box. On Mon, 28 Apr 2025 23:38:24 -0400 "Daniel W3DF via groups.io" <danflan49@...> wrote: And a newer version power supply board. My R7 has the older one. Will the
new one work in an older R7?
I don't want to destroy anything by trying to use this newer PS board. -- 73 -Jim NU0C
|
Re: R7 parent board pin out
Many thanks for the info Jim.? I have a spare Regulator Board, which currently does not work in my R7....? And a newer version power supply board.? My R7 has the older one.? Will the new one work in an older R7?? I don't want to destroy?anything by trying to use this newer PS board.
BTW, today I replaced the regulator board's 4700 uf cap and now my voltages are closer to correct.? Over 12v? out of the regulator board and 10.3v on the 10V rail on the PS board.? I think this R7 has had PS problems in it's past.? Four of the pins on the regulator board have been very hot because the molex connector has turned brown there.
Thanks again for your help.
73, Dan (W3DF)
On Mon, 28 Apr 2025 00:58:03 -0400
"Daniel W3DF via " <danflan49=[email protected]> wrote:
> Yes... I replaced the 220 uf on both the regulator board and the power
> supply board today.? I am also going to replace the 4700 uf capacitor.
> Changing the 220s did not change any of the voltages... still 11.8v instead
> of 13.8v and 11v instead of 10v.? The caps run warm, especially the 220 uf
> on the power supply board, it gets a little hot. I cannot get the voltages
> right with the adjustment pots.? I checked the resistors on the regulator
> board and they are OK and I think the pot is OK too.? I turn it fully
> clockwise to get 11.8v.? Does line voltage affect this much?? I'm running
> it on 115vac? Since I cannot get the power supply board out I cannot get to
> the resistors.
The 220uF on the PS board will run warm because it is essentially filtering square wave ripple from the mutltivibrator oscillator. That's why I recommend a high quality 105C cap. Harder to find in axial, but possible. I would use a 35V part.
It almost sounds like something is drawing too much current. Do you have a scope? If so, check for excessive ripple at the output of the bridge rectifier. The variable regulators on both boards are bog standard 723 circuits which are mature technology. Barring component value drift you should be able to dial in the voltages with no trouble. As has been said, check your Molex connectors thoroughly. Unplug the Power Supply board and see if you can adjust the Regulator to spec. You can also try running the rig from external DC and see if you can net the +10v.
> Are the old and new version power supply boards plug-in compatible?
Yes.
> The R7 works fine the way it is, but there is one strange problem... on the
> BC band switch positions I hear this randomly wandering heterodyne on
> several spots on the dial that interferes with weaker BC signals.
> Sometimes it will wander off to another frequency.
That could be spurs from the 23 KHz multivibrator oscillator on the PS board. Usually they are about 23 KHz apart and will wander a bit.
I am attaching the PS board BOM per your request. I did notice one thing I had not seen before. My R7A has the late version board so I had not looked at the early board much. There is an added capacitor on the schematic that is not present on the TR7 version of this board, C1919. It is shown as a 1000uF from the primary center tap of the transformer to ground. It is NOT listed on the BOM on shown in the pictorial. Which makes me want to open up another R7 so see what is there. If you do have that capacitor it should he replaced as well by the same logic as C1908, as it has been worked hard. If you don't have it, don't worry about it at this point. It is either a late addition or an artifact of a part that was removed from the build. We don't know which at this point and TR7 boards seem to work fine without it.
It is also worth noting that the PS board has two independent ground circuits which connect to the parent board. You have one ground for +10/+5, and another for the +24/-5. Check both.
--
73
-Jim
NU0C
|
Re: TR-4 Decreased Sensitivity on High Bands
The list I shared was with the dummy load connected.
I got the rig a few years ago and, aside from fixing a bad Zener diode in the PTO, I didn't do very much with it so I don't know how well it used to work.
I went through more of the alignment that is covered in basically the transmitter sections and getting T7, T8, T9, and T10 adjusted a bit better seemed to help 10M.? I haven't had time to do very much on-the-air testing with it but, noise-wise, I don't have to increase the audio gain as much as before for 10M so I think that's improvement.? I'm not sure, but I think I'm getting more power out but I haven't hooked up the MN-2000to get some better watts-out readings.? I hope to get some time with it tomorrow for that.
Okay on the saturation point.? That makes sense.
Oh, and, I slipped the PTO gear a bit and now I can get the moveable window closer to the center when using the calibrator.? That was annoying me...
Thanks again, Barry - N4BUQ
I assume your table of AGC voltages is with no antenna connected?
The calibrator should come in at ~S8 or so on 10 meters so you are pretty far down. It seems your receiver has more baseline noise on the lower bands, so the AGC voltage is responding to this exactly as it should. It is not unexpected that a receiver lacking high frequency gain would show less AGC response on the higher bands. Has the radio always been this way or did it once work for you and then fail? Bad tubes can certainly account for a radio¡¯s loss of TX drive and ?RX sensitivity. I would check this out before any alignment, or other efforts are undertaken. The commonality of the performance in both RX and TX does, however, indicate an alignment issue. Alignments (and drift thereof) are more critical as the operating frequency goes up (in older radios). Thus the previous stages that are common to all bands need to produce more drive than needed for the lower bands in order to have enough drive for the higher bands (in both TX and RX). One test I have found to be useful is to plot output power on a given band versus position of the TX gain pot on the different bands. If you find that ?the saturation point of output (the point at which increasing the gain position produces no increase in output) versus position of the pot does not change as you go up in bands, then likely you have an alignment issue or a drive issue before the final mixer, because these earlier stages should produce more output than needed on the low bands to make up for poorer efficiency on the higher bands. In other words, you should be able to drive the heck out of the radio on 80 meters well before the saturation point of the TX gain pot.? Receiver gain issues track TX gain issues religiously. If TX gain is weak, receiver gain will be weak too. Gary W0DVN On Apr 28, 2025, at 7:44?PM, Ham Radio via groups.io <bernard.murphy@...> wrote:
Steve: I assume you meant AGC. ? I have a TR-4 that has the same issue. ? Fine on TX but low on RX. ? See attached file.
--
73, Bernie. VE3FWF
Real?radios glow in the dark
<TR-4-tubes-sensitivity.xls>
|
Re: TR-4 Decreased Sensitivity on High Bands
Which relay did you clean?
Barry - N4BUQ
The one I¡¯m working on goes intermittent all bands but 15 and 10 are both weak, transmit and receive.?
Cleaned the relay but long term that hasn¡¯t helped. Replaced 4 dodgy tubes.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Apr 28, 2025 at 20:44, Ham Radio via groups.io <bernard.murphy@...> wrote:
Steve: I assume you meant AGC. ? I have a TR-4 that has the same issue. ? Fine on TX but low on RX. ? See attached file.
--
73, Bernie. VE3FWF
Real?radios glow in the dark
|
Re: TR-4 Decreased Sensitivity on High Bands
The one I¡¯m working on goes intermittent all bands but 15 and 10 are both weak, transmit and receive.?
Cleaned the relay but long term that hasn¡¯t helped. Replaced 4 dodgy tubes.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Apr 28, 2025 at 20:44, Ham Radio via groups.io < bernard.murphy@...> wrote:
Steve: I assume you meant AGC. ? I have a TR-4 that has the same issue. ? Fine on TX but low on RX. ? See attached file.
--
73, Bernie. VE3FWF
Real?radios glow in the dark
|
Re: R7 parent board pin out
On Mon, 28 Apr 2025 00:58:03 -0400 "Daniel W3DF via groups.io" <danflan49@...> wrote: Yes... I replaced the 220 uf on both the regulator board and the power
supply board today. I am also going to replace the 4700 uf capacitor.
Changing the 220s did not change any of the voltages... still 11.8v instead
of 13.8v and 11v instead of 10v. The caps run warm, especially the 220 uf
on the power supply board, it gets a little hot. I cannot get the voltages
right with the adjustment pots. I checked the resistors on the regulator
board and they are OK and I think the pot is OK too. I turn it fully
clockwise to get 11.8v. Does line voltage affect this much? I'm running
it on 115vac Since I cannot get the power supply board out I cannot get to
the resistors. The 220uF on the PS board will run warm because it is essentially filtering square wave ripple from the mutltivibrator oscillator. That's why I recommend a high quality 105C cap. Harder to find in axial, but possible. I would use a 35V part. It almost sounds like something is drawing too much current. Do you have a scope? If so, check for excessive ripple at the output of the bridge rectifier. The variable regulators on both boards are bog standard 723 circuits which are mature technology. Barring component value drift you should be able to dial in the voltages with no trouble. As has been said, check your Molex connectors thoroughly. Unplug the Power Supply board and see if you can adjust the Regulator to spec. You can also try running the rig from external DC and see if you can net the +10v. Are the old and new version power supply boards plug-in compatible? Yes. The R7 works fine the way it is, but there is one strange problem... on the
BC band switch positions I hear this randomly wandering heterodyne on
several spots on the dial that interferes with weaker BC signals.
Sometimes it will wander off to another frequency. That could be spurs from the 23 KHz multivibrator oscillator on the PS board. Usually they are about 23 KHz apart and will wander a bit. I am attaching the PS board BOM per your request. I did notice one thing I had not seen before. My R7A has the late version board so I had not looked at the early board much. There is an added capacitor on the schematic that is not present on the TR7 version of this board, C1919. It is shown as a 1000uF from the primary center tap of the transformer to ground. It is NOT listed on the BOM on shown in the pictorial. Which makes me want to open up another R7 so see what is there. If you do have that capacitor it should he replaced as well by the same logic as C1908, as it has been worked hard. If you don't have it, don't worry about it at this point. It is either a late addition or an artifact of a part that was removed from the build. We don't know which at this point and TR7 boards seem to work fine without it. It is also worth noting that the PS board has two independent ground circuits which connect to the parent board. You have one ground for +10/+5, and another for the +24/-5. Check both. -- 73 -Jim NU0C
|
Re: TR-4 Decreased Sensitivity on High Bands
I assume your table of AGC voltages is with no antenna connected?
The calibrator should come in at ~S8 or so on 10 meters so you are pretty far down.
It seems your receiver has more baseline noise on the lower bands, so the AGC voltage is responding to this exactly as it should. It is not unexpected that a receiver lacking high frequency gain would show less AGC response on the higher bands.
Has the radio always been this way or did it once work for you and then fail? Bad tubes can certainly account for a radio¡¯s loss of TX drive and ?RX sensitivity. I would check this out before any alignment, or other efforts are undertaken.
The commonality of the performance in both RX and TX does, however, indicate an alignment issue. Alignments (and drift thereof) are more critical as the operating frequency goes up (in older radios). Thus the previous stages that are common to all bands need to produce more drive than needed for the lower bands in order to have enough drive for the higher bands (in both TX and RX).
One test I have found to be useful is to plot output power on a given band versus position of the TX gain pot on the different bands. If you find that ?the saturation point of output (the point at which increasing the gain position produces no increase in output) versus position of the pot does not change as you go up in bands, then likely you have an alignment issue or a drive issue before the final mixer, because these earlier stages should produce more output than needed on the low bands to make up for poorer efficiency on the higher bands. In other words, you should be able to drive the heck out of the radio on 80 meters well before the saturation point of the TX gain pot.?
Receiver gain issues track TX gain issues religiously. If TX gain is weak, receiver gain will be weak too.
Gary
W0DVN
toggle quoted message
Show quoted text
On Apr 28, 2025, at 7:44?PM, Ham Radio via groups.io <bernard.murphy@...> wrote:
Steve: I assume you meant AGC. ? I have a TR-4 that has the same issue. ? Fine on TX but low on RX. ? See attached file.
--
73, Bernie. VE3FWF
Real?radios glow in the dark
<TR-4-tubes-sensitivity.xls>
|
Re: Pairing 2-NT with 2-B -- sidetone connection?
Craig,
I usually do listen to my transmitted signal as my sidetone.? My homebrew T/R switchbox switches the antenna from RX to TX and grounds the receiver antenna input.? Works well, especially with my homebrew transmitters.? But I thought I'd try the 2-NT's built-in sidetone just to see how it does.?
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Re: R7 12 vdc regulator board
My solution is to run my R7/A from an external power supply. My regulator board is in good shape but I have a 20 Amp variable Astron right there, so why not? The two-pin Foster connector can be found online. On Mon, 28 Apr 2025 10:26:42 -0700 "Paul W5NTQ via groups.io" <paulnkatz@...> wrote: For those who have had the unfortunate experience with your R7 12 VDC regulator board, you know what I mean.? If your board does burn up, just replace with IC regulator in place of power transistor on the heat sink on the back of the receiver. -- 73 -Jim NU0C
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FWIW I have not had a real need for any of the N7NB mods. The PBT is much more effective than an audio filter. What will help is a good outboard DSP. My favorite is the ClearSpeech base but I also use a JPS NIR-12 which sill slice signals to within an inch of their lives. But they are an augment to the PBT, not a replacement. I'm not a big CW man so QSK has never been attractive to me. To each his own. Fan controllers are sexy but IMO the temperature stability inside the radio will likely be less compromised unless you put a temperature sensor on the PTO. On Mon, 28 Apr 2025 04:48:39 -0700 "Craig W8CS via groups.io" <craig_severson@...> wrote: Curious if anyone has done any of these mods ( /g/DRAKE-RADIO/files/TR-7/TR7%20Visible%20modification.pdf ) to their TR-7 as suggested by Scott/N7NB?
Dug out the "Family Affair" ( ) book the other day and saw the list of mods, same as the article that Jim S posted.
The audio filter sounds like a no-brainer as I find myself engaging PBT just to tone down the harsh highs.
Would love to add true QSK as well although looks challenging.
--
Craig/W8CS
Greenville, SC -- 73 -Jim NU0C
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Re: TR-4 Decreased Sensitivity on High Bands
Steve: I assume you meant AGC. ? I have a TR-4 that has the same issue. ? Fine on TX but low on RX. ? See attached file.
--
73, Bernie. VE3FWF
Real?radios glow in the dark
|
Craig: Many thanks for your interest in the four modifications I developed for the TR7 back in 1991/1992 (I can¡¯t believe it was that long ago). In terms of building/installing these modifications today, component availability has changed significantly since I originally published these modifications, but it¡¯s still feasible to build and install these modifications today if you¡¯re willing to make a few component substitutions. I¡¯ll begin with the QSK card; historically it¡¯s been the most popular TR7 modification. In order to meet the PIN diode carrier lifetime and forward resistance requirements necessary to handle 150W across the TR-7¡¯s 1.8-30 MHz range, my QSK Board design was originally based on the M/A Com MA4P4002D high-power PIN diode. Unfortunately, M/A Com discontinued the MA4P4002D several years ago, but a reduced power version of this diode (MA4P4002B) is still available. The power dissipation of the MA4P4002D was specified at 15W, which was necessary for high duty-cycle operation (e.g., RTTY operation at full power). The power dissipation of M/A Com¡¯s current MA4P4002B PIN diode is specified as 5.5 W with ?¡± leads (see M/A Com¡¯s spec sheet at: ). Unless high duty-cycle operation is required (e.g., >50% per minute), the MA4P4002B with ?¡± leads suspending the diode above the board makes it an excellent substitute for the MA4P4002D. The RX protection relay (K2002) in my original QSK board design calls for a Magnacraft W104AM1PA2. There¡¯s nothing special about the W104AM1PA2; any 12V SPST reed relay can be used in its place. That said, minor modifications to K2002¡¯s traces on the QSK card may be required depending upon the form factor and pinout of the substitute reed relay you select. The components necessary for the Front End board are readily available except the Aromat RSD-12 relays (K1001-K1004). These relays were readily available on the surplus market at a very reasonable price in the early 1990¡¯s. Today these relays are still available, but they¡¯re very expensive primarily because of their shielded design and their unique pinout. For some time now I¡¯ve been considering developing a new Front End board based on readily available relays, but I haven¡¯t had the time to do so. Like the QSK card, any 12 V SPDT relays will work in place of the Aromat RSD-12 if they¡¯re not too large, but some creativity may be required to match the substitute relay¡¯s pinout to the Front End board¡¯s foil layout for K1001-K1004. The bottom line is that the Front End board can be built as specified in my article but the relays are expensive (potential workarounds are available). The QSK card can be constructed as described in my article using substitute components if your TX duty cycle requirements at full power are in the 50% per minute range. I¡¯m more than happy to answer any questions you may have, but some of my responses may be delayed. In spite of being retired I have many irons in the fire and my ability to correspond can change significantly from day to day. 73, Scott N7NB ? ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Craig W8CS via groups.io
Sent: Monday, April 28, 2025 4:49 AM
To: [email protected]
Subject: [DRAKE-RADIO] TR-7 Mods by N7NB?? Curious if anyone has done any of these mods to their TR-7 as suggested by Scott/N7NB?? Dug out the book the other day and saw the list of mods, same as the article that Jim S posted.? The audio filter sounds like a no-brainer as I find myself engaging PBT just to tone down the harsh highs.? Would love to add true QSK as well although looks challenging.?
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Re: Pairing 2-NT with 2-B -- sidetone connection?
perhaps take the easy way out and monitor your own signal for sidetone? The secondary benefit is that you know you're on frequency as well.?
--
Craig/W8CS
Greenville, SC
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Pairing 2-NT with 2-B -- sidetone connection?
I'd like to pair a 2-NT transmitter with a 2-B receiver.? The 2-NT manual says to connect the sidetone output to the grid of the receiver's audio amp or to the arm of the receiver's volume control (see below).? Would this be a direct connection, or through a series capacitor, or ???? Since the 2-NT has a sidetone level control, I'm thinking I should connect the sidetone directly to pin 8 of the 8BN8 so that it's independent of the receiver's volume level.? Thoughts??
?
?
?
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R7 12 vdc regulator board
The R7 and TR7 use Molex tin plated pins in the plug in printed circuit boards.? Tin to tin contacts oxidize and become high resistance.? For those to have corrected problems in the 7-line equipment by unplugging and plugging back in the PCBs that cleans the oxide on the tin contacts and corrects the problem for awhile (don't forget to use DeOxit ProGold when doing so).? A more insidious problem is when high current has to pass through these tin contacts.? Oxidation, higher resistance then heat and board failure.? For those who have had the unfortunate experience with your R7 12 VDC regulator board, you know what I mean.? If your board does burn up, just replace with IC regulator in place of power transistor on the heat sink on the back of the receiver.? If your regulator board is still working, highly recommend replacing the tin plated Molex connectors on the regulator board with connectors having gold plated contacts.? That will reduce oxidation of the contacts and failure of the PCB.? Collins used all gold plated contacts on the KWM/HF-380 connectors.? I've never had a connector contact problem with my KWM-380 in 30 years.? Drake was saving a few dollars on each 7-Line radio by using all tin plated connector contacts and created a reliability problem for us years later. ?
?
73,
Paul W5NTQ
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Interesting. Quite a lofty project considering the features are standard in today's most basic econobox.? Everything checks out on paper, but the QSK RF management might be problematic, and BOM needs updating to current production components before I would tackle it. At this point though, I've come to admire profound vintage equipment to accurately reflect the state of the art in it's time, especially TR-7. But I will gladly cheer you on from EN30 Oscar Papa, over!? 73, Jim WA9Z ?
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Jim Shorney
Ham Radio
Craig W8CS