Re: Drake TR-7 - Noisy transmitter
It is exactly as stated. The adjustment is an old school ceramic trimmer cap conveniently placed on the board in line with the key jack on the rear panel. Since you need key down CW to hear the side tone it becomes a one-handed adjustment to slide a small flat blade screwdriver through the key jack to both key the rig and adjust the trimmer. You do not need to have the drive turned up to do this. How you measure the 800 Hz audio tone is up to you. If you have a frequency counter that works well in the audio range that would be the obvious choice. Simply connect it across the rig's speaker. You could also use an accurate audio generator set to 800 Hz and connected to a small speaker to zero beat the CW side tone using your ears. Another option would be a Windows or Linux computer with the Fldigi digital mode software installed. You can accurately measure an audio frequency with Fldigi. Extreme accuracy is not required but I would suggest that you not go too far away from 800 Hz as that is the design center of the oscillator circuit. Which also makes the math easier. Drake's CW is a bit different than most other rigs. Modern rigs typically shift the RX frequency to hear a CW tone and the dial displays the zero beat (carrier) frequency. The TR7 is exactly the opposite. We shift the TX up 800 Hz and the dial displays the offset frequency. Your zero beat frequency is dial frequency +800 Hz. If you want to work someone on, say, 7010 you need to set your dial frequency to 7009.2 to be on his frequency. Re: a bench test jig, depending on the circuit you are troubleshooting you don't always need all the voltages to test a "naked" board. Much of the time you would only need +10. I have swept the IF filters from a couple of rigs using only +10 to turn on the desired signal path and negative volts from a 18650 cell to bias off the other signal paths. I used component lead clippings shoved into in the Molex connectors and alligator clip test leads to make the connections. A bit ugly but it worked FB. On Sat, 08 Feb 2025 06:48:58 -0800 "atlasstuff via groups.io" <g4fph@...> wrote: I tried to adjust the CW sidetone on the TR7, but could not understand the Drake procedure for this. Something about a screwdriver and the KEY jack! Are you able to shed any light here, please? -- 73 -Jim NU0C
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Re: Wanted Manual for AC4R power supply upgrade.
Manual has has been sent.
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On Feb 7, 2025, at 6:25 PM, George Cortez Jr via < ne2i@...> wrote:
I did email Mike also. Much appreciated!
Thanks
George NE2I
On Friday, February 7, 2025 at 05:59:42 PM EST, KB9VY via < lcoblentz3@...> wrote:
I have a paper copy I could scan for you. I can probably get it done this weekend. I¡¯m sure Mike Bryce probably has a pdf available ? ?Larry - KB9VY
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Re: Drake TR-7 - Noisy transmitter
Jim,
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There have been several times I could have used a bench test jig for Drake boards. Just a simple thing with 5, 10 and 13 Volt supplies and some AF and RF generation and detection facilities. One day I might encounter a fault that will tip me into making one. I do have a surplus PBT / REF Board which I bought as 'untested' for no money (and only because it was no money). Of course, untested = does not work, so I should fix that at some point to turn it into a viable spare.
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The Jumper Board has certainly proved it's worth while fixing the TR4310. A further useful service tool would be a small PCB that would plug vertically into the Translator Board, not covering anything else up, and programme it to work on some convenient band for testing. The deluxe version could have a DIP switch for range.
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According to my Chinese tester, all of the tants. I removed are OK. My guess is that one of them, given applied operating voltage and time, started to breakdown when in circuit.
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I tried to adjust the CW sidetone on the TR7, but could not understand the Drake procedure for this. Something about a screwdriver and the KEY jack! Are you able to shed any light here, please?
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Regards,
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Mark, G4FPH.
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T-4XC Final Cathode Resistors
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.?
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Checked the final Cathode resistors which are 15ohm/1Watt. They are running at 18/17.5 ohms, roughly 20% high.?
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- Is there a specific type of resistor composition that you prefer to replace these with??
- Recommended to upgrade larger than 1W??
TIA
--
Craig/W8CS
Greenville, SC
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Re: Drake TR-7 - Noisy transmitter
Hi Mark, On Fri, 07 Feb 2025 05:03:31 -0800 "atlasstuff via groups.io" <g4fph@...> wrote: I could not see a way of having the Transmit Exciter Board on extenders at the same time as keeping the radio running using the Jumper Board to replace the DR7 / Display Board. Did I miss a trick here? The trick is to power the board up on the bench from a 10V power supply. You can do a lot of troubleshooting this way. My attitude to parts replacement - especially capacitors - is hardening. I've never been fond of blanket / just in case replacement, but tantalums can cause a lot of collateral damage and undeserved misery when they go short-circuit. Generally, if I pull a capacitor out to test, these days, I replace with new regardless of the test results. In this case, I replaced old tantalum with new tantalum. If I had had low-value electrolytics to hand, I would probably have used those instead as it was an LF / audio application. Good detective work. I think I would have looked at the ceramic coupling cap first. They can go bad or become microphonic. Tantalums have an undeserved bad rap. They are very reliable unless they have been abused. High surge current, reversed polarity, and excessive soldering heat are the most common forms of abuse. It would have been interesting to find out if one of your tants is actually failing. Before re-installing the DR7, I changed the key electrolytic capacitors around the power feed in and the two 5 Volt regulators on this board. Some years ago I decided to completely re-cap one of my TR7s just to see if I could notice any difference. I did not. AFAIC the only "must replace" capacitor in the TR7 is C2108 on the power supply board. It WILL fail sooner or later and strange things will happen. Will try drilling them out. If that doesn't work, push out the PEM nuts using a hydraulic press and try tapping the holes left behind in the chassis for some suitable metric screws. that probably won't work well. There was a reason Drake used PEMs there. Full disclosure, I detest PEMs. However with aluminum that thin your tapped threads will be very weak, if you can get any cut at all. Sheet metal screws would do better but would be easy to over-tighten and strip out. -- 73 -Jim NU0C
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Re: Wanted Manual for AC4R power supply upgrade.
I did email Mike also. Much appreciated!
Thanks
George NE2I
On Friday, February 7, 2025 at 05:59:42 PM EST, KB9VY via groups.io <lcoblentz3@...> wrote:
I have a paper copy I could scan for you. I can probably get it done this weekend. I¡¯m sure Mike Bryce probably has a pdf available ? ?Larry - KB9VY
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Re: Wanted Manual for AC4R power supply upgrade.
Ive looked around and have not found any.? Thanks
George NE2I
On Friday, February 7, 2025 at 06:07:13 PM EST, Richard Knoppow via groups.io <1oldlens1@...> wrote:
? ? Isn't it on line somewhere?? I have done two of the Heathkit Shop
upgrades but think I got only an instruction sheet with them. I don't
think he has changed the circuit any. Or have I missed something?
On 2/7/2025 2:55 PM, George Cortez Jr via groups.io wrote:
> I need the manual only. Does anyone have a pdf of it?
> Thanks....
>
> Yahoo Mail - Email Simplified <https://mail.onelink.me/107872968?
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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Re: Wanted Manual for AC4R power supply upgrade.
Isn't it on line somewhere? I have done two of the Heathkit Shop upgrades but think I got only an instruction sheet with them. I don't think he has changed the circuit any. Or have I missed something?
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On 2/7/2025 2:55 PM, George Cortez Jr via groups.io wrote: I need the manual only. Does anyone have a pdf of it?
Thanks....
Yahoo Mail - Email Simplified <
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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Re: Wanted Manual for AC4R power supply upgrade.
I have a paper copy I could scan for you. I can probably get it done this weekend. I¡¯m sure Mike Bryce probably has a pdf available ? ?Larry - KB9VY
On Fri, Feb 7, 2025 at 5:55 PM, George Cortez Jr via groups.io < ne2i@...> wrote: I need the manual only. Does anyone have a pdf of it?
Thanks....
On Fri, Feb 7, 2025 at 5:09 PM, Dean N2TNN via groups.io
<N2tnn@...> wrote:
I bought the one on eBay with the wires attached and just did my second upgrade. Total time 90 minutes. Attaching the new boards to the chassis took half that time. Remember to tag each wire that you clip because the colors are faded and you might put them in wrong holes.
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I clipped the old components and used high heat to melt solder when the new wires were added.
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You get the schematic and the new updated version.
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I had fun doing it and learned something new. Win, Win
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73, Dean/ N2TNN
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?
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Re: Wanted Manual for AC4R power supply upgrade.
I need the manual only. Does anyone have a pdf of it? Thanks....
On Fri, Feb 7, 2025 at 5:09 PM, Dean N2TNN via groups.io <N2tnn@...> wrote:
I bought the one on eBay with the wires attached and just did my second upgrade. Total time 90 minutes. Attaching the new boards to the chassis took half that time. Remember
to tag each wire that you clip because the colors are faded and you might put them in wrong holes.
?
I clipped the old components and used high heat to melt solder when the new wires were added.
?
You get the schematic and the new updated version.
?
I had fun doing it and learned something new. Win, Win
?
73, Dean/ N2TNN
?
?
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tnx Craig, your post has strengthened my resolve
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Tom W2TF
On Thursday, February 6, 2025 at 06:06:08 PM EST, Evan via groups.io <k9sqg@...> wrote:
That question might best be answered by YLs/XYLs.
I've moved several times in the past few years. And each time I pack stuff up and haul it to the next location, I look at everything and ask, "Do I REALLY need this?"
?
I did this over and over again with the pile of test gear and cabling. Some things did not make the latest cut, like all those scraps of LMR400 that I was saving for "some day."?
?
So cut to my latest project; I'm bringing to life a C-Line (again) after 25 years of dormancy. And being that the AC-4 was original from 1977 with no mods, I knew I was living on borrowed time. I just did Mike's (Heathkit Shop) board upgrade, and I was thinking as I finished it, "Boy, sure would be great to have a Variac for the smoke test."?
?
I did some digging in the attic and ....Son of a B...there it was. The Variac that I've been hauling around for the past 40 years. I had even forgotten that I still owned it.?
?
Worked perfectly.?
?
So for all of you wondering if you need all your stuff for "some day"...the answer is YES.?
--
Craig/W8CS
Greenville, SC
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Re: Wanted Manual for AC4R power supply upgrade.
I bought the one on eBay with the wires attached and just did my second upgrade. Total time 90 minutes. Attaching the new boards to the chassis took half that time. Remember
to tag each wire that you clip because the colors are faded and you might put them in wrong holes.
?
I clipped the old components and used high heat to melt solder when the new wires were added.
?
You get the schematic and the new updated version.
?
I had fun doing it and learned something new. Win, Win
?
73, Dean/ N2TNN
?
toggle quoted message
Show quoted text
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Re: Wanted Manual for AC4R power supply upgrade.
?
? ? ? ? This is the URL for the kit.
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peek at this post.
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ED WA6WGS
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Wanted Manual for AC4R power supply upgrade.
I have an old original AC4R kit (2004) that was never assembled and do not have the manual.?
?
Thanks
?
George NE2I
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Re: Drake TR-7 - Noisy transmitter
Almost one year since I parked the TR7 with the 'crackly audio' transmitter. How time flies!
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With the TR4310 now fixed, it was time to finish the TR7. Oddly, I had a couple of contacts on it with no trace of crackling. Then, during a third contact (after the radio had been powered up for many hours), the transmit audio went cracky, noisy, distorted and would not stop. Disconnecting the microphone and just shorting PTT to ground on the front-panel microphone socket with a screwdriver, I could vary the level of the crackling from zero to a good 50 W PEP, or more, using the mic. gain control. So, whatever was cracking, was before the mic. gain pot. In a TR7, there's not much active circuitry to consider - just a simple, two BJT amplifier.
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I could not see a way of having the Transmit Exciter Board on extenders at the same time as keeping the radio running using the Jumper Board to replace the DR7 / Display Board. Did I miss a trick here?
?
Pulling the Transmit Exciter board, I noticed several low-value tantalum capacitors and, yes, two of them (C310 and C309) were in key positions coupling the transmit audio. In my experience, these were the most likely culprits, so I changed them. I did not bother changing C307, a 0.05 uF disc ceramic (coupling) capacitor. I can't remember ever finding a bad capacitor of this type in any of my vintage radio and took the risk that this case would prove no different. In addition, I changed several other tantalum capacitors, adjacent to the mic. amplifier circuitry, as I did not want to have to pull the board ever again. I also changed a quantity of electrolytic capacitors in key coupling and de-coupling positions in and around the balanced modulator an board generally.
?
My attitude to parts replacement - especially capacitors - is hardening. I've never been fond of blanket / just in case replacement, but tantalums can cause a lot of collateral damage and undeserved misery when they go short-circuit. Generally, if I pull a capacitor out to test, these days, I replace with new regardless of the test results. In this case, I replaced old tantalum with new tantalum. If I had had low-value electrolytics to hand, I would probably have used those instead as it was an LF / audio application.
?
Before re-installing the DR7, I changed the key electrolytic capacitors around the power feed in and the two 5 Volt regulators on this board.
?
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On test, the transmit audio is now clear and clean and got good reports on 40 m SSB. I've not checked way down to see if the 1 kHz low level artifacts (which seemed to be display multiplex related) have improved / gone, but will do so at some point.
?
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Almost time to put the covers back on. As part of doing that I have to do something about the 80% of the base plate screws a previous owner managed to break off in the PEM nuts. Will try drilling them out. If that doesn't work, push out the PEM nuts using a hydraulic press and try tapping the holes left behind in the chassis for some suitable metric screws.
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Regards,
?
Mark, G4FPH.
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At last, the promised follow-up on the T-4XC which was sticking on tx. It turned out to be the relay switching tube (6FQ7 in this set).
On the tester (I have an AVO VCM Mk3) the original showed as slightly leaky/gassy, probably not enough to worry about in many applications but the T4 has high resistance feed into the grid and leakage of a few uA is enough to drag the 'off' bias voltage down to where the tube conducts enough for the relay to pull in.
It took an age for the replacement to arrive but all seems good now.
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I also looked at the relay, the PA switching contacts had a lot of debris around them and are well worn. I've suggested the owner starts saving to get a replacement (around $80 over here).
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Again, thanks for all the suggestions, great bunch of .people here.
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73, Steve G8GSQ
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Semiconductor List Closing
Hello, fwllow Drakesters...
I had a more-than-anticipated response to my semiconductor list.? This email hereby closes-off the request period.
I will now printo out all the requests and allocate accordingly.? My aim was to keep devices that are in common use stocked here for future use.? Example, MPF102 I need at least 5 to stay in invenroty here (as mentioned).? Rare devices like the UHF power transistors, I'd be happy to sell all of.
All requests from USA will have $5 added for shipping.? I figure I can get anything anywhere for $5, including any padded envelopes (I'll use my Amazon envelopes until they're gone).
Anything to Canada, if you can provide a USA mailing address, that would be GREAT.? Customs forms are now a major PITA and I avoid them like I'd avoid a jellyfish.
Hope to have final amounts over the weekend (life events, notwithstanding)...
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
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That question might best be answered by YLs/XYLs.
I've moved several times in the past few years. And each time I pack stuff up and haul it to the next location, I look at everything and ask, "Do I REALLY need this?"
?
I did this over and over again with the pile of test gear and cabling. Some things did not make the latest cut, like all those scraps of LMR400 that I was saving for "some day."?
?
So cut to my latest project; I'm bringing to life a C-Line (again) after 25 years of dormancy. And being that the AC-4 was original from 1977 with no mods, I knew I was living on borrowed time. I just did Mike's (Heathkit Shop) board upgrade, and I was thinking as I finished it, "Boy, sure would be great to have a Variac for the smoke test."?
?
I did some digging in the attic and ....Son of a B...there it was. The Variac that I've been hauling around for the past 40 years. I had even forgotten that I still owned it.?
?
Worked perfectly.?
?
So for all of you wondering if you need all your stuff for "some day"...the answer is YES.?
--
Craig/W8CS
Greenville, SC
|
I've moved several times in the past few years. And each time I pack stuff up and haul it to the next location, I look at everything and ask, "Do I REALLY need this?"
?
I did this over and over again with the pile of test gear and cabling. Some things did not make the latest cut, like all those scraps of LMR400 that I was saving for "some day."?
?
So cut to my latest project; I'm bringing to life a C-Line (again) after 25 years of dormancy. And being that the AC-4 was original from 1977 with no mods, I knew I was living on borrowed time. I just did Mike's (Heathkit Shop) board upgrade, and I was thinking as I finished it, "Boy, sure would be great to have a Variac for the smoke test."?
?
I did some digging in the attic and ....Son of a B...there it was. The Variac that I've been hauling around for the past 40 years. I had even forgotten that I still owned it.?
?
Worked perfectly.?
?
So for all of you wondering if you need all your stuff for "some day"...the answer is YES.?
--
Craig/W8CS
Greenville, SC
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Has anyone successfully transplanted filters from a TR-4/4c into a TR-3? ?I have a nice TR-3 and a trashed TR-4 for a donor. ?
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Jim Shorney
Craig W8CS
