Re: Small lamp reference for Drake L7
Tim,
Have you already attempted a calibration via the pot on the back panel of the RF deck?
73,
Evan, K9SQG
Hello group. I need to replace the meter shunts for the Drake L7, LV and HV reading low. From the schematic Drake used 8 2.3 meg 1/2 watt resistors it appears from the schematic and manual pictures they are located right behind the 3-500Zs. Any advice gladly accepted.
Tim
WB8UHZ
On Saturday, January 4, 2025 at 03:14:00 PM EST, Mohamed VA2MKX via groups.io <va2mkx@...> wrote:
Thanks a lot for the reference, appreciated ! :)
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Re: Small lamp reference for Drake L7
Hello group. I need to replace the meter shunts for the Drake L7, LV and HV reading low. From the schematic Drake used 8 2.3 meg 1/2 watt resistors it appears from the schematic and manual pictures they are located right behind the 3-500Zs. Any advice gladly accepted.
Tim
WB8UHZ
On Saturday, January 4, 2025 at 03:14:00 PM EST, Mohamed VA2MKX via groups.io <va2mkx@...> wrote:
Thanks a lot for the reference, appreciated ! :)
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Jim:
Not sure which one is "blown".? But all four ceramic feedthroughs shown in the pic are .001 uf/350V rated.
But.....your HV line (+650VDC) is missing where the unused hole is.? Is this what you were referring to?? If so, there is no feedthrough capacitor at that point.? A wire carrying the B+ high voltage to the PA tubes passes through a piece of friction fit plastic insulation.? You will have to make your own - shouldn't be too hard.? All 4 line transmitters are the same in this?regard.
73 Peter VE7PS
Can anyone recommend a subsitute for a blown feed-thru cap that I need ?
?
Appreciate any help?
?
Regards
?
W6TTY
?
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Can anyone recommend a subsitute for a blown feed-thru cap that I need ?
?
Appreciate any help?
?
Regards
?
W6TTY
?
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yes it was a very pleasant surprised when I turned it on and it worked, The problem?I have now id that?when i SWITCH FROM lsb OR usB TO cw i get a signal in the receiver 5 over 9 and if I press the morse key I hear the tone as well. It does not seem to mute that signal. I also noticed that if I use the PBT I can hear?a tone and can swing the passband and I can go back?and forth past it. Almost?sounds like an oscillation. Any ideas? Thanks,
Jim VE1RB
Well, there ya go! Nice catch. Doesn't it feel good? That is an interesting failure. Just a wild guess but I am thinking the lead had a weak spot, maybe a nick or a spot of corrosion, that caused it to break after years of thermal cycling.
On Sat, 4 Jan 2025 07:19:51 -0400
"Jim Harris via " <radiove1rb=[email protected]> wrote:
> I just wanted to let you know I managed to get the high VCO working. I
> was removing transistors and checking them on my tester, and when I
> removed Q504 and noticed that the Gate lead was broken off half way down
> to the board. I tested it and it was okay so had thought I had done that
> so I put it back in and soldered the lead together. Put the radio back
> together and decided to see what the DR7 readout said and the radio
> happened to be on the 10 meter band and it was showing the correct
> frequency. Checked 15 meter and that was working as well. I still have
> one problem but will post later on that. My thanks for all the help on
> this problem to everyone.
>
> Jim VE1RB
--
73
-Jim
NU0C
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Re: Small lamp reference for Drake L7
Thanks a lot for the reference, appreciated ! :)
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Re: R4C Sherwood audio mod questions
I stand corrected.? Rob, NC0B
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Paul Christensen via groups.io
Sent: Saturday, January 04, 2025 6:52 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C Sherwood audio mod questions
?
On Sat, Jan 4, 2025 at 05:19 AM, Floyd - K8AC wrote:
>The text specifies the inverting input capacitor as 200 uF while the schematic shows it as 330 uF.
The computed -3 dB high-pass turnover frequency is 123 Hz for 330 uF, and 204 Hz for 200 uF.? Pick either one based on personal roll-off preference.
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Re: R4C Sherwood audio mod questions
Hi Floyd,
?
Thanks for pointing that out.? I¡¯ll look at the board in my R-4C and see which is correct. It likely doesn¡¯t make much difference with the inverting input impedance.
?
Rob, NC0B
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Floyd - K8AC via groups.io
Sent: Saturday, January 04, 2025 6:19 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C Sherwood audio mod questions
?
Rob - maybe it makes no difference at all, but there is a discrepancy in the component values for the AMP-4.? The text specifies the inverting input capacitor as 200 uF while the schematic shows it as 330 uF.
73 & Happy New Year, Floyd - K8AC
|
Well, there ya go! Nice catch. Doesn't it feel good? That is an interesting failure. Just a wild guess but I am thinking the lead had a weak spot, maybe a nick or a spot of corrosion, that caused it to break after years of thermal cycling. On Sat, 4 Jan 2025 07:19:51 -0400 "Jim Harris via groups.io" <radiove1rb@...> wrote: I just wanted to let you know I managed to get the high VCO working. I
was removing transistors and checking them on my tester, and when I
removed Q504 and noticed that the Gate lead was broken off half way down
to the board. I tested it and it was okay so had thought I had done that
so I put it back in and soldered the lead together. Put the radio back
together and decided to see what the DR7 readout said and the radio
happened to be on the 10 meter band and it was showing the correct
frequency. Checked 15 meter and that was working as well. I still have
one problem but will post later on that. My thanks for all the help on
this problem to everyone.
Jim VE1RB -- 73 -Jim NU0C
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Re: R4C Sherwood audio mod questions
Thank you to all and to Rob especially.? This is all very helpful - all gold.
Nigel
On Sat, Jan 4, 2025 at 05:19 AM, Floyd - K8AC wrote:
?
>The text specifies the inverting input capacitor as 200 uF while the schematic shows it as 330 uF.
?
The computed -3 dB high-pass turnover frequency is 123 Hz for 330 uF, and 204 Hz for 200 uF.? Pick either one based on personal roll-off preference.
?
Paul, W9AC?
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Re: T-4XC Sideband adjustments?
Tweak the cxr osc....such that the low end rolls off the same on LSB? as it does on USB.? ?That's as good as it will get.?
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Re: R4C Sherwood audio mod questions
On Sat, Jan 4, 2025 at 05:19 AM, Floyd - K8AC wrote:
?
>The text specifies the inverting input capacitor as 200 uF while the schematic shows it as 330 uF.
?
The computed -3 dB high-pass turnover frequency is 123 Hz for 330 uF, and 204 Hz for 200 uF.? Pick either one based on personal roll-off preference.
?
Paul, W9AC?
|
Re: R4C Sherwood audio mod questions
Rob - maybe it makes no difference at all, but there is a discrepancy in the component values for the AMP-4.? The text specifies the inverting input capacitor as 200 uF while the schematic shows it as 330 uF.
?
73 & Happy New Year, Floyd - K8AC
|
I just wanted to let you know I managed to get the high VCO
working. I was removing transistors and checking them on my
tester, and when I removed Q504 and noticed that the Gate lead was
broken off half way down to the board. I tested it and it was okay
so had thought I had done that so I put it back in and soldered
the lead together. Put the radio back together and decided to see
what the DR7 readout said and the radio happened to be on the 10
meter band and it was showing the correct frequency. Checked 15
meter and that was working as well. I still have one problem but
will post later on that. My thanks for all the help on this
problem to everyone.
Jim VE1RB
?
On 2025-01-01 20:17, Jim Harris via
groups.io wrote:
toggle quoted message
Show quoted text
Yes Gary that does interest me a lot. We will talk
about that and make a deal I hope. Many thanks for the offer.
Jim VE1RB
On Wed, Jan 1, 2025 at 5:33?PM
Gary Follett via <xntrick1948= [email protected]>
wrote:
You know, the VCO board in the TR7 is the same as the one
in the R7. I happen to have a working R7 VCO board if this
interests you.
Gary
W0DVN
Okay
I will get it out and have a look see.?
Jim
VE1RB
On Wed, Jan 1,
2025 at 5:28?PM Gary Follett via ??<xntrick1948= [email protected]>
wrote:
Well, your 30 MHz scope is not entirely
useless. Even though the ~80 MHz VCO will be
severely attenuated, you should still be
able to see it and determine what it looks
like That VCO signal is pretty stout at the
point at which you are observing it (several
volts per to peak).
Gary
W0DVN
Gary
the frequency counter is hook to
5/24. I will check the input to
the two 5 volt regulators and let
you know. I do have ?a scope but
it only goes to 30 mhz but I know
where I can get a good 100 MHz
one. Will get that as soon as I
can and have a looks at those
outputs. Many thanks Gary for all
your help otherwise I would be
working in the dark.?
Jim
VE1RB
On Wed, Jan
1, 2025 at 4:45?PM Gary
Follett via ??<xntrick1948= [email protected]> wrote:
If that oscillator is
showing anything real (~152
MHz) then it is being
selected. This selection is
enacted by the application
of +10 volts on U502. The
VCO board has no other
information about the band
selected by the band switch.
The only other
information the VCO gets
from the outside world
comes in via pin 5/9 (500
KHz Reference) and pin
5/11 (this is roughly 500
KHz as well, and is the
result of the 40 MHz
Reference, the PTO and the
VCO signal divided by N (N
being the selected number
produced by the band
selection logic) and this
is the signal that closes
the PLL loop.
However, even with the
loop open and unlocked,
the frequency at the
output of the VCO should
never exceed 80 MHz,?
Where are you
measuring the 152 MHz?
If grounding RFC505
on the away end does
nothing, try grounding
the other end. If
still no change, then
ground the physical
junction at CR511A, B
and CR510 A,B. This
should pull the
frequency down a lot.
If not, ground the
Drain of Q504 through
a capacitor of about
0.01 uF. That should
clearly kill any
oscillation and remove
any output from the
VCO.
Then humor me on
this one - measure the
voltage on the inputs
of both 5 volt
regulators U501 and
U502 when a low band
(less than 15 MHz) and
a high band (greater
than 15 MHz) are
selected by the band
switch. If there is a
switching issue,
perhaps BOTH VCO¡¯s are
on when High Band is
selected. I would have
a hard time deriving
what would happen in
this condition but I
am quite sure things
would not go well.
This is when an
oscilloscope would
be handy. You could
look at the waveform
at the output of the
VCO, at pin 5/24,
the output of the
VCO to the radio.
You should see ?a
nice sine wave of
roughly constant
amplitude when
either VCO is
selected.
Gary
W0DVN
Gary
I tried that
ground on
RFC505 and no
change. Is it
not getting
band
information?
Jim
VE1RB
On Wed, Jan 1, 2025 at 3:02?PM Gary Follett via ??<xntrick1948= [email protected]>
wrote:
If you
are reading
152 MHz, the
you should
ground RFC505
on the end
away from the
varactor
diodes. The
frequency
should come
down.
Gary
W0DVN
Jim
maybe this
will help. I
touched up
several solder
joints
although they
didn¡¯t look
good but not
cracked. I
switched the
input to the
counter and it
is reading 17
to 18 mhz ?
<IMG_1166.jpeg>
as the
frequency is
jumping around
so is not
locked. I
wonder if that
is a clue??
Jim
VE1RB
On Wed, Jan 1, 2025 at 12:52?PM Jim Harris via ??<radiove1rb= [email protected]> wrote:
Good
ideas Jim and
I will get at
doing that
today. It is
windy and
raining here
quite hard. A
good job
inside hi hi.
I will let you
know how it
goes. Many
thanks for the
suggestions?and help.
Jim VE1RB
At this point
I am
suspicious of
that 1.3 MHz
reading. That
may be a
spurious
reading. It
seems to me
that the VCO
should not be
able to run
there. What is
the level of
the signal?
The frequency
determining
components are
L502 and the
varactor
diodes. Resist
the temptation
to try to
adjust L502.
As a long time
tech told me
back in the
dim past, when
you have a
failure "it is
never the
alignment".
At this point
I think I
would inspect
the solder
connections in
the high VCO
circuit under
magnification
and good
lighting. You
could have a
failed joint
or via. Check
the voltages
on the three
JFETs. C156 or
C517 could be
suspect. You
have a working
low VCO to
compare
voltage and
resistance
readings to.
On Wed, 1 Jan
2025 07:41:18
-0400
"Jim Harris
via?" <radiove1rb=[email protected]> wrote:
> Yes Gary
I did the
ground on
RFC505? when
looking at the
frequency on?
> the
counter and it
does drop a
lot. So I
guess you are
saying the
High?
> VCO is
oscillating at
1.3 MHz . If
that is the
case there
must be?
> something
wrong on that
board unless
the info it
gets is wrong.
Hope?
> this
helps.
--?
73
-Jim
NU0C
|
At a guess the smaller magnet was Alnico 5 or some other metallic magnet material while the larger one was ceramic. Ceramic magnets are very powerful but do not conduct magnetism well so tend to be large. Ceramic is much cheaper than metal magnets so tended to displace them. It is the field strength of the magnet that is important so the physical size may not make a difference. In my little essay on speakers I mentioned the choice between overall efficiency and low frequency response. If one does not need extended low frequency response a speaker may be made quite efficient. Again the break point of efficiency depends on the cone size. Efficiency drops rapidly below the frequency where the wavelength is less than about the circumference of the cone. I am not sure what you mean by back frame magnet nor by end-user variations. FWIW, the first cone speakers are attributed to Chester Rice at General Electric but I think these may have been balanced armature type, my memory is throwing me. The more modern moving coil speaker is attributed to Peter Jensen, who, with a partner (name burried in memory) began Magnavox. However, I have seen patents issued to Western Electric showing a moving coil speaker mechanism which seems to predate both of these. On 1/3/2025 4:52 PM, Paul Christensen via groups.io wrote: Over the course of MS4 production, Drake used at least two different speaker driver variations.? One has a large magnet, roughly the size of the SSN replacement being discussed.? I¡¯ve seen two minor variations of that magnet, one unpainted, and the other painted black.
The second form of speaker is of the type more commonly seen in vintage consumer-grade radios in which a much smaller back-frame magnet is used.? I¡¯ve seen enough of both used in MS4 speakers to conclude that these are not differences based on end-user variations.
Paul, W9AC
Richard Knoppow Los Angeles WB6KBL SKCC 19998
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40m cw at night in a big contest is a good time to rediscover the rf gain. :)
John k5mo
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It is not just hiss that is an issue. The wide range speaker will faithfully reproduce any out of band distortion products present in the audio. On Fri, 03 Jan 2025 16:42:31 +0000 "Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote: I¡¯ll add my practical experience here. I¡¯ve used Minimus-7 (and its variants) for some time and I find the sound to be quite nice with them.
The problem with hiss is more a function of the audio amp. Roll-off the hiss and problem solved. -- 73 -Jim NU0C
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Re: VE3EFJ third mixer mod for the R4C
I did not roll of the high frequencies in the TDA2003 Audio Power Amplifier. The low-level audio stages were completely redesigned as the Drake system really sucked!
Bob K9JU
On Wednesday, January 1, 2025 at 11:05:09 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
Did you alter the feedback network to roll off above the speech range? May of the reference designs built around these are for hi-fi bandwidth.
On Wed, 1 Jan 2025 21:07:48 +0000 (UTC)
"Bob Loving via groups.io" <bob.loving@...> wrote:
>? Many years ago, I designed a PC board for the TDA 2003 Audio Amplifier. Like some have noted, the hiss level was/is a bit too high if you listen when wearing "cans."?
--
73
-Jim
NU0C
|
Well, it actually does make a signal more listenable by reducing the noise floor. On Fri, 03 Jan 2025 17:04:01 +0000 "Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote: Yes. The RFG control isn¡¯t nearly as important on most receivers that were purpose-built for SSB ¡ª i.e., with product detectors.
I¡¯ll sometimes play with the RFG during contests but rarely otherwise.
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
Sent from [Proton Mail]() for iOS
On Fri, Jan 3, 2025 at 11:46, rls19 via groups.io <[rls19@...](mailto:On Fri, Jan 3, 2025 at 11:46, rls19 via groups.io <<a href=)> wrote:
This technique was developed originally for receivers that did not have product detectors. Envelope detection is much more sensitive to the ratio of local oscillator level versus signal level, so the signal level going into the second mixer had to be kept low enough for proper demodulation by "riding" the RF gain control.
73, Bob AD3K
---------------------------------------------------------------
From: [email protected] <[email protected]> on behalf of Evan via groups.io <k9sqg@...>
Sent: Friday, January 3, 2025 11:05 AM
To: [email protected] <[email protected]>
Subject: Re: [DRAKE-RADIO] TR7 Audio
I learned this as a new novice from my mentor, since "Elmer" was out of style. It helps to reduce the effects of lightning and QRM.
73,
Evan, K9SQG
On Friday, January 3, 2025 at 12:21:28 AM EST, Tony Yamin <tony92646@...> wrote:
I've seen instruction manuals where you adjust the AF gain to a 'comfortable' level and use the RF gain as a volume knob.
I learned to operate this way in my early days and, as I understand, it helps keep the RF noise out-of-the-radio!
--
TNX-n-73's fer now....
KF6JS - Tony -- 73 -Jim NU0C
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Re: T-4XC has a "condition"
Agree Gary....I have never set bias by turning "all controls to the left".? Just make sure the GAIN pot at ZERO....CCW.? Seems to have always worked in the past for me.? Good hunch about possible 10m oscillations!? I'm home Sunday and will give that a try if I get a chance.? Will keep Dean posted here on the group site.
73 Peter VE7PS
On Fri, Jan 3, 2025 at 4:31?PM Gary WB6OGD via <winbladgary= [email protected]> wrote: On Fri, Jan 3, 2025 at 12:28 PM, VE7PS wrote:
I can't experiment with one of my own rigs today or tomorrow, but I'll be able to do that likely on Sunday.? I am now anxious to see if I can duplicate what you are seeing with the RF Tune rotated clockwise into the high end of the 10m band setting.
?
?
If there is a difference (there should NOT be), it probably indicates the need for neutralization.? 10meters is where the final can most easily
break into oscillation if not neutralized properly (and with a correctly working transmitter).
?
I would set the bias on the lower bands, and on SSB with the gain at zero... and after I nulled the carrier!? If the radio is working correctly,
that bias point should hold on all bands, if it doesn't something is wrong.
?
73,
Gary
WB6OGD
?
?
?
?
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Rob Sherwood
Jim Shorney
Paul Christensen
Floyd - K8AC