Re: Drake service CDs no longer available from K4OAH?
I believe Garey is a silent key. He sure helped me a lot.?
--
Richard
WB5NEN
|
Re: Strange AUX-7 for TR-7
OK, let's try this, the AUX-7 works fine, I don't need it, would
anyone like to buy it? Thanks, Adam W4AJF
toggle quoted message
Show quoted text
My first TR7 had the AUX, sold it when I downsized/renovated our
house some years back.
my second one
does not have AUX. Not to berate those who want... but I just
did the PC trace cut and enabled all band XMIT and I just use
the buttons on front to move to the area. For me the WARC are
a 'bit' of a hoax.. wherein I don't see much on 30m...some on
12 and 17 re. activity sometimes. i know band solar condx
affect but it seems after all this time since WARC 1979 those
bands still have not really caught on generally, IMHO.Hence I
am happy with the extra work just using the buttons to get to
WARC areas.
That said, there
once was a time I did seem to have a pipeline on 17m and
worked Africa quite a bit as well as a few commercial planes
in transit. So there is/was activity there. Maybe I just don't
spend enough time in the chair with a radio waiting for The
Big Trout to come into the river from his lair....
That said... my
CW filters are old in that rig.. hollow and ringing...rig is
no fun in that state.... so I have already contacted Noble to
get new filters once and for all.... or the rig goes to
someone who will KNOW they can only use it on SSB as it
currently stands.
Brian VE3HI
------ Original Message ------
From: david.w5xu@...
To: [email protected]
Sent: Wednesday, March 22, 2023 3:55 PM
Subject: Re: [DRAKE-RADIO] Strange AUX-7 for TR-7
yes, the ones I have are by Farr radio.
Look them up. If still in business you can get the info
there. Let me know otherwise.
David Assaf III
W5XU, VP8RXU
On Wed, Mar 22, 2023 at
3:32?PM Adam Farber < adamf@...>
wrote:
Yes, I understand that, I was trying to see if
anyone knew the maker and had a paperwork on it. Thanks,
Adam
It’s a homebrew Aux7 fill in board to open
up 12,17, and 30 if I remember. I built one and used
it until I got my real Aux7 bird.
|
Re: R4C power supply question
" I? never found tube life a problem with the elevated filament voltage. "
I have a vintage text around here somewhere focused specifically on tube (receiving) longevity studies? and among the variables they looked at, filament voltage was the primary driver of reduced usable life.
John
On Wed, Mar 22, 2023 at 2:04?PM Rob Sherwood < rob@...> wrote:
Hi Steve,
?
I used the Sartori “sold tubes” in the 3rd mixer position for a while until he went out of production.? Then I designed my MIX-4 replacement.? There
were two versions with different mixer components (40673 & later the SA602).?
?
Before I figured out how RFI hash was getting into the 3rd mixer I used a 1:1 120 volt shielded isolation transformer to keep the hash from getting
to the receiver.
?
Rob, NC0B
?
From: [email protected] [mailto:[email protected]]
On Behalf Of Steve Wedge, W1ES/4 via
Sent: Wednesday, March 22, 2023 11:58 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C power supply question
?
I definitely noticed the hash on the audio when I bought my first later-production R-4C and spent a fair amount of time trying to tame it.? The location of that third mixer
and its design meant that very small differences in shield locations, variations in individual 6EJ7 tubes, etc., were critical to how well the 3rd mixer worked.? I was lucky in that doing the Sartori circuit tamed it enough that I could ignore whatever artefacts
were still there.? The early R-4C, with the 6HS6 mixers, didn't have this issue at all.? I agree that the performance of that mixer really threw a wet blanket on the whole experience but I did keep that C Line for a few years and even did some contesting with
it.? By that time, we were starting to hear the siren song of the Kenwood TS-930S and I made the switch in the late 80s.
I have since discovered that one can cherrypick 6EJ7's from a bunch of NOS tubes and get one that reduces the hash almost enough to not need to change any circuitry.
I still love the sharpness of the R-4C filters and have a C Line that works pretty well, stone-stock.
Time flies like an arrow.? Fruit flies like a banana.
------- Original Message -------
On Wednesday, March 22nd, 2023 at 12:59 PM, Rob Sherwood <rob@...> wrote:
Hi Doug,
?
Please see comments inserted below.
?
Rob, NC0B
?
From: [email protected] [mailto:[email protected]]
On Behalf Of Doug Crompton WA3DSP
Sent: Tuesday, March 21, 2023 11:28 PM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C power supply question
?
Rob,
Yes I completely rebuilt the supply adding a 7812 regulator board which are dirt cheap on Amazon and elsewhere. I also added an LM380 audio board. again, dirt cheap, and everything runs from regulated 12V. I use 3 diodes in series to lower the low voltage to
the 7812 to about 14.5-15 volts and the 7812 loafs along.
?
Reply:? I never used your diode idea, and at least the way I used a copper strap from the 7812 to the chassis, 17 volts into the regulator was a non-issue.?
I used the LM-383T which puts out more power than the LM-380, but 100mW produces plenty of audio with a typical high efficiency speaker. I also used the LM-383T in my SE-3 AM sync detector, but running on 18 volts instead of 12 volts.
My R4C never had the C201 as far as I remember although I ripped quite a bit off the power supply board. There is no heat there anymore. I do have some very low level hum that is coming from somewhere ahead of the volume pot. It is absolutely clean with the
pot disconnected. It is very low level, but being a purist, I was looking for possible fixes.
?
Reply:? My engineer carefully specified how my LM-383T audio amp board had to have a single ground return. Otherwise there would be a ground-loop hum problem.?
That is likely what you are observing.?
I wonder if others have measured filament voltage. I used several digital meters and they all agreed that the filaments were running at about 7.0-7.1 volts. This is with a 121 volt line. I figured I needed about .3 ohms to lower it so I wound about 6 feet of
#30 enameled wire on a high value 2W resistor which dropped it about .5 volts or so.
Reply:? Yes the typical filament voltage is slightly higher than +10% above nominal 6.3 volts on
most of the hundreds of R-4Cs that came through my shop.? I recently was dealing with an R-4C that took 5 minutes to warm up, and the filament voltage was 6.1 volts.? I never came up with a solution to the slow warmup.? I never found tube life a problem with
the elevated filament voltage.?
I was also wondering when the LM380 first came out. The earliest data I can find is an app note dated 1972, so it had to be early in the R4C production, My R4C is SN 28387 which is very close to the end of production in 1976 or later so it certainly could have
had a much better power supply and audio amp at that late date.? Think of the space that would have been saved as most of the powers supply and audio boards would have gone away, I guess by 1976 they were working on the TR7 design which used the newer chips.
?
Reply:? Drake is notorious for using big dropping resistors in products.? Look at the L-4B power supply and all the heat in those large resistors.? The
TR-7 wasn’t any better with all the heat in regulators sinked to the chassis near the PTO.? Also why put the 100 watt PA right by the PTO??? Why put the R-4C power transformer right behind the PTO?? The earlier Drake R-4, R-4A and R-4B receivers had the power
transformer oriented 90 degrees from where it is in the R-4C.? In the R-4C case, the transformer magnetic field couples into the PTO slug-tuned inductor causing hum sidebands on the PTO output. If you operate the PTO outside the radio it has no line-related
sidebands.? If you remove the R-4C power transformer, punch two new holes in the chassis, and remount the transformer 90 degrees from normal (as it is in earlier models), the line-related hum sidebands on the PTO signal are drastically lower.? Please see attached
PDF from my 2012 Drake Dayton Forum presentation.
?
COMMENTS:? Consider the parts count in the TR-7 DR-7 board with all those TTL chips.? The parts count on that board, and likely many others, could have
been drastically reduced, decreasing assembly time and cost.? The change in the R-4C from 6HS6 mixer tubes to 6EJ7s, and the subsequent circuit change for LO injection, was a terrible step backwards.? Any RFI noise on the AC line passed right into the grid
of the 3rd mixer.? That didn’t happen with the 6HS6 circuit.? Drake did well for decades in spite of design errors and the lack of production updates that would have saved money and made the products better. I wonder if the culture at Drake had
been more proactive whether the TR-8 would? have had a chance in the market?? David Assaf W5XU is the TR-8 guru, but I don’t know whether a schematic even exists for the TR-8.? Was it designed well?? I? have no idea. ?????
?
73, Rob, NC0B
Doug, WA3DSP
?
|
Re: Strange AUX-7 for TR-7
My first TR7 had the AUX, sold it when I downsized/renovated our house some years back. my second one does not have AUX. Not to berate those who want... but I just did the PC trace cut and enabled all band XMIT and I just use the buttons on front to move to the area. For me the WARC are a 'bit' of a hoax.. wherein I don't see much on 30m...some on 12 and 17 re. activity sometimes. i know band solar condx affect but it seems after all this time since WARC 1979 those bands still have not really caught on generally, IMHO.Hence I am happy with the extra work just using the buttons to get to WARC areas. That said, there once was a time I did seem to have a pipeline on 17m and worked Africa quite a bit as well as a few commercial planes in transit. So there is/was activity there. Maybe I just don't spend enough time in the chair with a radio waiting for The Big Trout to come into the river from his lair.... That said... my CW filters are old in that rig.. hollow and ringing...rig is no fun in that state.... so I have already contacted Noble to get new filters once and for all.... or the rig goes to someone who will KNOW they can only use it on SSB as it currently stands. Brian VE3HI
------ Original Message ------
From: david.w5xu@...
To: [email protected]
Sent: Wednesday, March 22, 2023 3:55 PM
Subject: Re: [DRAKE-RADIO] Strange AUX-7 for TR-7
yes, the ones I have are by Farr radio. Look them up. If still in business you can get the info there. Let me know otherwise.
David Assaf III W5XU, VP8RXU
On Wed, Mar 22, 2023 at 3:32?PM Adam Farber < adamf@...> wrote: Yes, I understand that, I was trying to see if anyone knew the maker and had a paperwork on it. Thanks, Adam It’s a homebrew Aux7 fill in board to open up 12,17, and 30 if I remember. I built one and used it until I got my real Aux7 bird.
|
Re: Strange AUX-7 for TR-7
yes, the ones I have are by Farr radio.? Look them up.? If still in business you can get the info there.? Let me know otherwise.
David Assaf III W5XU, VP8RXU ?
On Wed, Mar 22, 2023 at 3:32?PM Adam Farber < adamf@...> wrote:
Yes, I understand that, I was trying to see if anyone knew the maker
and had a paperwork on it. Thanks, Adam
It’s a homebrew Aux7 fill in board to open up 12,17, and 30 if I
remember. I built one and used it until I got my real Aux7 bird.
|
Re: Strange AUX-7 for TR-7
Actually, now that I remember, Far circuits is who I bought the board from. Bob, you are not that far from me, I'm in Kingston, about 30 miles west of Knoxville.
toggle quoted message
Show quoted text
On Wed, Mar 22, 2023 at 04:49 PM, Bob Loving wrote:
?
Adam, FAR Circuits made (or maybe still makes) that diode matrix board for the three lowest ranges (~0 to 1.500-MHz) plus the three WARC bands. I made my own version per a QST article in the 1982 July issue, pp 20-22 with PCB overlay on p36. I have one of the FAR boards and made my own PCB from the QST article. If that is the coverage you want for quick access, the board you have is fine.?
?
73,
Bob Loving K9JU
Maryville, TN
?
On Wednesday, March 22, 2023 at 04:32:01 PM EDT, Adam Farber <adamf@...> wrote:
?
?
Yes, I understand that, I was trying to see if anyone knew the maker and had a paperwork on it. Thanks, Adam
It’s a homebrew Aux7 fill in board to open up 12,17, and 30 if I remember. I built one and used it until I got my real Aux7 bird.
?
|
Re: Strange AUX-7 for TR-7
I have several in use and they work great.? I will try to find the info on it and will email you.? The factory Aux 7 board uses plug in modules that have diodes inside.? The arrangement of the diodes gives the freq coverage.? So, it is the same principle as the original, just does not have the plug in modules. So far have 4 of these in use and no issues.? There are 8 positions on the front face dial and there are 8 possible combos of diodes to give you the band coverage.? Pick a band and then the instructions tell you what band position and what diodes go where.? Easy and effective. David Assaf III W5XU, VP8RXU ?
On Wed, Mar 22, 2023 at 3:32?PM Adam Farber < adamf@...> wrote:
Yes, I understand that, I was trying to see if anyone knew the maker
and had a paperwork on it. Thanks, Adam
It’s a homebrew Aux7 fill in board to open up 12,17, and 30 if I
remember. I built one and used it until I got my real Aux7 bird.
|
Re: Strange AUX-7 for TR-7
There was an article in the July 1982 edition of QST that has all the info on it. I can't post it on here for copyright reasons but if you are a member of the ARRL you can search for the back issue that has the write up in it with the schematic and all. The board was originally created by Robert Morrow WB6GTM and he was the one who wrote the article up for QST. That's the callsign on the back of the board I bought just last year new, I believe he still sells them.
|
Re: Strange AUX-7 for TR-7
Adam, FAR Circuits made (or maybe still makes) that diode matrix board for the three lowest ranges (~0 to 1.500-MHz) plus the three WARC bands. I made my own version per a QST article in the 1982 July issue, pp 20-22 with PCB overlay on p36. I have one of the FAR boards and made my own PCB from the QST article. If that is the coverage you want for quick access, the board you have is fine.?
73, Bob Loving K9JU
Maryville, TN
On Wednesday, March 22, 2023 at 04:32:01 PM EDT, Adam Farber <adamf@...> wrote:
Yes, I understand that, I was trying to see if anyone knew the maker
and had a paperwork on it. Thanks, Adam
It’s a homebrew Aux7 fill in board to open up 12,17, and 30 if I
remember. I built one and used it until I got my real Aux7 bird.
|
Re: Strange AUX-7 for TR-7
Yes, I understand that, I was trying to see if anyone knew the maker
and had a paperwork on it. Thanks, Adam
toggle quoted message
Show quoted text
It’s a homebrew Aux7 fill in board to open up 12,17, and 30 if I
remember. I built one and used it until I got my real Aux7 bird.
|
Re: Strange AUX-7 for TR-7
It’s a homebrew Aux7 fill in board to open up 12,17, and 30 if I remember. I built one and used it until I got my real Aux7 bird.
|
Re: Strange AUX-7 for TR-7
Hi Jim, I don't know what that means?? Adam
toggle quoted message
Show quoted text
Nice Job Adam.
73, Jim VE1RB
On Wed, Mar 22, 2023 at
4:25?PM Adam Farber < adamf@...>
wrote:
>
>> Hi all, I bought a TR-7 and it had this home made
AUX-7 that appears
>> to be made by W0YVZ. His QRZ information shows only a
partial invalid
>> e-mail address and nothing on the internet turns up
him linked to the
>> AUX-7. Does anyone have any information on this AUX-7
or who really
>> made it?
>>
>> Thanks for any help.
>>
>> Adam Farber W4AJF
>> Cooper City, FL
|
Re: Strange AUX-7 for TR-7
Nice Job Adam.
73, Jim VE1RB
On Wed, Mar 22, 2023 at 4:25?PM Adam Farber < adamf@...> wrote:
>
>> Hi all, I bought a TR-7 and it had this home made AUX-7 that appears
>> to be made by W0YVZ. His QRZ information shows only a partial invalid
>> e-mail address and nothing on the internet turns up him linked to the
>> AUX-7. Does anyone have any information on this AUX-7 or who really
>> made it?
>>
>> Thanks for any help.
>>
>> Adam Farber W4AJF
>> Cooper City, FL
|
Re: DRAKE TECHNICAL NET UPDATE ( March 19, 2023 )
I would be game to have a 20 meter net meet...Especially since 20 has been on fire.
On Wed, Mar 22, 2023 at 3:42 PM, Henry Dorkin <Hdorkinmd@...> wrote:
I’ll give it a?try….!
Hank WM1V? ex-WN2HOS
On Wed, Mar 22, 2023 at 11:42?AM Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote: So, out of the gang here, how many of you would probably check-in to a 20m net on the weekends?? Let's see if this is worth pursuing.? I can certainly help out here, as I'm definitely on 20 with a decent signal (I can pick an L7 or a 30L-1).
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with Proton Mail secure email.
------- Original Message -------
On Wednesday, March 22nd, 2023 at 1:15 PM, Lyndon Nerenberg (VE7TFX/VE6BBM) <lyndon@...> wrote:
> I would be game to try 20m, although I don't know if my 2nd-floor-balcony
> doublet will put out any sort of signal on that band. I'll have a better
> idea later this week when I finish stringing it up and wire it in to the
> tuner.
>
> --lyndon
>
>
>
|
Re: DRAKE TECHNICAL NET UPDATE ( March 19, 2023 )
I’ll give it a?try….!
Hank WM1V? ex-WN2HOS
On Wed, Mar 22, 2023 at 11:42?AM Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote: So, out of the gang here, how many of you would probably check-in to a 20m net on the weekends?? Let's see if this is worth pursuing.? I can certainly help out here, as I'm definitely on 20 with a decent signal (I can pick an L7 or a 30L-1).
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with Proton Mail secure email.
------- Original Message -------
On Wednesday, March 22nd, 2023 at 1:15 PM, Lyndon Nerenberg (VE7TFX/VE6BBM) <lyndon@...> wrote:
> I would be game to try 20m, although I don't know if my 2nd-floor-balcony
> doublet will put out any sort of signal on that band. I'll have a better
> idea later this week when I finish stringing it up and wire it in to the
> tuner.
>
> --lyndon
>
>
>
|
Re: Strange AUX-7 for TR-7
Hi all, I bought a TR-7 and it had this home made AUX-7 that appears to be made by W0YVZ. His QRZ information shows only a partial invalid e-mail address and nothing on the internet turns up him linked to the AUX-7. Does anyone have any information on this AUX-7 or who really made it?
Thanks for any help.
Adam Farber W4AJF
Cooper City, FL
|
Re: DRAKE TECHNICAL NET UPDATE ( March 19, 2023 )
Looking forward to the net! Wayne Smith
toggle quoted message
Show quoted text
On Mar 22, 2023, at 1:48 PM, Bill Leonard N0CU <billincolo73@...> wrote:
? On Wed, Mar 22, 2023 at 11:42?AM Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote: So, out of the gang here, how many of you would probably check-in to a 20m net on the weekends?? Let's see if this is worth pursuing.? I can certainly help out here, as I'm definitely on 20 with a decent signal (I can pick an L7 or a 30L-1).
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with Proton Mail secure email.
------- Original Message -------
On Wednesday, March 22nd, 2023 at 1:15 PM, Lyndon Nerenberg (VE7TFX/VE6BBM) <lyndon@...> wrote:
> I would be game to try 20m, although I don't know if my 2nd-floor-balcony
> doublet will put out any sort of signal on that band. I'll have a better
> idea later this week when I finish stringing it up and wire it in to the
> tuner.
>
> --lyndon
>
>
>
|
Re: DRAKE TECHNICAL NET UPDATE ( March 19, 2023 )
toggle quoted message
Show quoted text
On Wed, Mar 22, 2023 at 11:42?AM Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote: So, out of the gang here, how many of you would probably check-in to a 20m net on the weekends?? Let's see if this is worth pursuing.? I can certainly help out here, as I'm definitely on 20 with a decent signal (I can pick an L7 or a 30L-1).
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with Proton Mail secure email.
------- Original Message -------
On Wednesday, March 22nd, 2023 at 1:15 PM, Lyndon Nerenberg (VE7TFX/VE6BBM) <lyndon@...> wrote:
> I would be game to try 20m, although I don't know if my 2nd-floor-balcony
> doublet will put out any sort of signal on that band. I'll have a better
> idea later this week when I finish stringing it up and wire it in to the
> tuner.
>
> --lyndon
>
>
>
|
Re: DRAKE TECHNICAL NET UPDATE ( March 19, 2023 )
I'm in Steve, as often as I can mid April thru late Nov. but for occasional travel to ON and AB, or whatever...like most retirees.? Working on a winter remote....but not with Drake radios.
As such, not suitable as net control - sorry.
73 Peter VE7PS
On Wed, Mar 22, 2023 at 10:42?AM Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote: So, out of the gang here, how many of you would probably check-in to a 20m net on the weekends?? Let's see if this is worth pursuing.? I can certainly help out here, as I'm definitely on 20 with a decent signal (I can pick an L7 or a 30L-1).
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with Proton Mail secure email.
------- Original Message -------
On Wednesday, March 22nd, 2023 at 1:15 PM, Lyndon Nerenberg (VE7TFX/VE6BBM) <lyndon@...> wrote:
> I would be game to try 20m, although I don't know if my 2nd-floor-balcony
> doublet will put out any sort of signal on that band. I'll have a better
> idea later this week when I finish stringing it up and wire it in to the
> tuner.
>
> --lyndon
>
>
>
|
Re: R4C power supply question
Hi Steve,
?
I used the Sartori “sold tubes” in the 3rd mixer position for a while until he went out of production.? Then I designed my MIX-4 replacement.? There
were two versions with different mixer components (40673 & later the SA602).?
?
Before I figured out how RFI hash was getting into the 3rd mixer I used a 1:1 120 volt shielded isolation transformer to keep the hash from getting
to the receiver.
?
Rob, NC0B
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Steve Wedge, W1ES/4 via groups.io
Sent: Wednesday, March 22, 2023 11:58 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C power supply question
?
I definitely noticed the hash on the audio when I bought my first later-production R-4C and spent a fair amount of time trying to tame it.? The location of that third mixer
and its design meant that very small differences in shield locations, variations in individual 6EJ7 tubes, etc., were critical to how well the 3rd mixer worked.? I was lucky in that doing the Sartori circuit tamed it enough that I could ignore whatever artefacts
were still there.? The early R-4C, with the 6HS6 mixers, didn't have this issue at all.? I agree that the performance of that mixer really threw a wet blanket on the whole experience but I did keep that C Line for a few years and even did some contesting with
it.? By that time, we were starting to hear the siren song of the Kenwood TS-930S and I made the switch in the late 80s.
I have since discovered that one can cherrypick 6EJ7's from a bunch of NOS tubes and get one that reduces the hash almost enough to not need to change any circuitry.
I still love the sharpness of the R-4C filters and have a C Line that works pretty well, stone-stock.
Time flies like an arrow.? Fruit flies like a banana.
------- Original Message -------
On Wednesday, March 22nd, 2023 at 12:59 PM, Rob Sherwood <rob@...> wrote:
Hi Doug,
?
Please see comments inserted below.
?
Rob, NC0B
?
From: [email protected] [mailto:[email protected]]
On Behalf Of Doug Crompton WA3DSP
Sent: Tuesday, March 21, 2023 11:28 PM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C power supply question
?
Rob,
Yes I completely rebuilt the supply adding a 7812 regulator board which are dirt cheap on Amazon and elsewhere. I also added an LM380 audio board. again, dirt cheap, and everything runs from regulated 12V. I use 3 diodes in series to lower the low voltage to
the 7812 to about 14.5-15 volts and the 7812 loafs along.
?
Reply:? I never used your diode idea, and at least the way I used a copper strap from the 7812 to the chassis, 17 volts into the regulator was a non-issue.?
I used the LM-383T which puts out more power than the LM-380, but 100mW produces plenty of audio with a typical high efficiency speaker. I also used the LM-383T in my SE-3 AM sync detector, but running on 18 volts instead of 12 volts.
My R4C never had the C201 as far as I remember although I ripped quite a bit off the power supply board. There is no heat there anymore. I do have some very low level hum that is coming from somewhere ahead of the volume pot. It is absolutely clean with the
pot disconnected. It is very low level, but being a purist, I was looking for possible fixes.
?
Reply:? My engineer carefully specified how my LM-383T audio amp board had to have a single ground return. Otherwise there would be a ground-loop hum problem.?
That is likely what you are observing.?
I wonder if others have measured filament voltage. I used several digital meters and they all agreed that the filaments were running at about 7.0-7.1 volts. This is with a 121 volt line. I figured I needed about .3 ohms to lower it so I wound about 6 feet of
#30 enameled wire on a high value 2W resistor which dropped it about .5 volts or so.
Reply:? Yes the typical filament voltage is slightly higher than +10% above nominal 6.3 volts on
most of the hundreds of R-4Cs that came through my shop.? I recently was dealing with an R-4C that took 5 minutes to warm up, and the filament voltage was 6.1 volts.? I never came up with a solution to the slow warmup.? I never found tube life a problem with
the elevated filament voltage.?
I was also wondering when the LM380 first came out. The earliest data I can find is an app note dated 1972, so it had to be early in the R4C production, My R4C is SN 28387 which is very close to the end of production in 1976 or later so it certainly could have
had a much better power supply and audio amp at that late date.? Think of the space that would have been saved as most of the powers supply and audio boards would have gone away, I guess by 1976 they were working on the TR7 design which used the newer chips.
?
Reply:? Drake is notorious for using big dropping resistors in products.? Look at the L-4B power supply and all the heat in those large resistors.? The
TR-7 wasn’t any better with all the heat in regulators sinked to the chassis near the PTO.? Also why put the 100 watt PA right by the PTO??? Why put the R-4C power transformer right behind the PTO?? The earlier Drake R-4, R-4A and R-4B receivers had the power
transformer oriented 90 degrees from where it is in the R-4C.? In the R-4C case, the transformer magnetic field couples into the PTO slug-tuned inductor causing hum sidebands on the PTO output. If you operate the PTO outside the radio it has no line-related
sidebands.? If you remove the R-4C power transformer, punch two new holes in the chassis, and remount the transformer 90 degrees from normal (as it is in earlier models), the line-related hum sidebands on the PTO signal are drastically lower.? Please see attached
PDF from my 2012 Drake Dayton Forum presentation.
?
COMMENTS:? Consider the parts count in the TR-7 DR-7 board with all those TTL chips.? The parts count on that board, and likely many others, could have
been drastically reduced, decreasing assembly time and cost.? The change in the R-4C from 6HS6 mixer tubes to 6EJ7s, and the subsequent circuit change for LO injection, was a terrible step backwards.? Any RFI noise on the AC line passed right into the grid
of the 3rd mixer.? That didn’t happen with the 6HS6 circuit. ?Drake did well for decades in spite of design errors and the lack of production updates that would have saved money and made the products better. I wonder if the culture at Drake had
been more proactive whether the TR-8 would? have had a chance in the market?? David Assaf W5XU is the TR-8 guru, but I don’t know whether a schematic even exists for the TR-8. ?Was it designed well?? I? have no idea. ?????
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73, Rob, NC0B
Doug, WA3DSP
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David
k5fex
Rob Sherwood