Re: Drake TR7, TX issue any ideas?
On further inspection I found this:
 ? Those 2 pin diodes connected to a cap? It looks like some modification, how ever I see no holes in the PCB where those 2 pin diodes would go otherwise.
Early version of this board and legit or?
?
Best 73's Michael.
|
Will a R4B and a T4XC transceive?? Is there any difference in the interconnections from if I were using R4B with T4XB?
?
Thanks and '73
?
Carl - W5SU
Dallas TX
?
|
Is it going to need anything special to hook it up to a Drake 4 line T-4XC. Without the nine volt battery.?
toggle quoted message
Show quoted text
On 2025-02-03 09:16, Lorne VE6CSR? via groups.io wrote:
> From the inside bottom of a Silver Eagle
> VE7LXX
>
Interesting.? Looks like that amp has an input impedance of about 1
megohm,
which is set by the base biasing resistor.
????????????????? - Jerry, KF6VB
|
On 2025-02-03 09:16, Lorne VE6CSR via groups.io wrote: From the inside bottom of a Silver Eagle
VE7LXX
Interesting. Looks like that amp has an input impedance of about 1 megohm, which is set by the base biasing resistor. - Jerry, KF6VB
|
From the inside bottom of a Silver Eagle?
VE7LXX
toggle quoted message
Show quoted text
While we are on the subject of Mics, can someone share the wiring diagram for a powered D104 with me?
On Monday, February 3, 2025 at 09:45:39 AM EST, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
This one has no foam but there¡¯s a white cottony-looking material that is right behind the grille. It looks identical to the Astatic 1011 I have. That mic does have a powered amp, which I run pretty low with my 4 Line sets. It also has a tone control,
which I run fully-up so I don¡¯t get muddy audio.?
The 1011 was made to have an amp in it ¡ª the two sliders in the base attest to that.?
The 7077 has never been powered. The work done inside the 7077 was obviously done after manufacture. The workmanship is terrible and everything is black electrical taped together.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sun, Feb 2, 2025 at 19:27, Jim Shorney via groups.io < jimNU0C@...> wrote:
You can find photos of the inside of a 7077 here:
/g/DRAKE-RADIO/album?id=252836
It does have a small transformer in it to step up the voltage output to drive a TR7. No capacitors. And a cheap CB-era dynamic cartridge hidden inside the head. After this many years the blast foam behind the grill will have decayed to crunchy dust. Both the
cartridge and the blast foal are easily replaceable.
On Sun, 02 Feb 2025 23:11:59 +0000
"Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote:
> I went on to the 7238 Drake Pre-net this afternoon and strange things were happening. I heard some noise in the speaker when the PTT was pressed and WB0IQK said that I sounded excessively tinny. I was fortunate to have my $10 GE-branded Shure 444, which worked
like a charm but, of course, I want to know what is wrong with the 7077, so I took it apart.
>
> Oy, vey! What a mess inside! Someone had put in a couple of capacitors (low value) and what looks like a transformer. It's all kludged in there, so I know this ain't no factory job! Lots of lousy workmanship and electrical tape trying to hold things together!
>
> The mic element I can't be sure if it's correct, though it looks like it all fits together like it should. The mic element measures around 430 ohms on my Fluke 77.
>
> Is this simply a case of the wrong element in this mic? The TR7 manual specifies a high Z mic. I am tempted to simply get a Heil element for high Z and being done with it.
>
> If any of you have a 7077 mic, can you measure resistance across the mic element for me? This should be from ground to pin 1 of the mic plug.
>
> TNX & 73,
>
> Steve Wedge, W1ES
--
73
-Jim
NU0C
|
Attached is a file I have on the amplified d104
Ralph ku4pt
On Monday, February 3, 2025 at 11:47:14 AM EST, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
Folks, I will go down to the shack this afternoon and take photos.? I'll also draw, schematically, what it looks like (by hand -- I don't have any CAD by which to do this).
One thing of note that I will repeat here is that the element itself -- disconnected from the rest of the mic -- measures 430 ohms with my Fluke 77 in resistance mode.? That seems odd if the thing is supposed to be high-impedance.? I thus am led to believe that someone went into this mic and changed the element, adding all of the transformer/capacitor bits.
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Monday, February 3rd, 2025 at 10:50 AM, Bill Losef via groups.io <w.losefsky@...> wrote:
While we are on the subject of Mics, can someone share the wiring diagram for a powered D104 with me?
?
|
Drake TR7, TX issue any ideas?
Hardly been using it for TX until recently, then I notice that on 10 Meter output is close to 2.5 watts..
Okay, not much.. On 15 meters the current draw is close to 31 amps to produce 100watts! Quite a bit.
more reasonably 21-22 amps on other bands.
So went for an TX alignment, if I crank up the pre drive I can get it up to ~60 watts on 10 meter
obviously not a good scenario and the dr7 board definitely does not like it as the display starts to be all over the place during TX,?
with pre drive fully cranked up 40 Meters the PA self oscillates, not good.
So my thoughts, something in the pre drive section or bandpass maybe?
Looking for any suggestions before going nuts down that route.
Thanks on advance!
Best Regards, Michael - oz8abr
|
Folks, I will go down to the shack this afternoon and take photos.? I'll also draw, schematically, what it looks like (by hand -- I don't have any CAD by which to do this).
One thing of note that I will repeat here is that the element itself -- disconnected from the rest of the mic -- measures 430 ohms with my Fluke 77 in resistance mode.? That seems odd if the thing is supposed to be high-impedance.? I thus am led to believe that someone went into this mic and changed the element, adding all of the transformer/capacitor bits.
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Monday, February 3rd, 2025 at 10:50 AM, Bill Losef via groups.io <w.losefsky@...> wrote:
While we are on the subject of Mics, can someone share the wiring diagram for a powered D104 with me?
On Monday, February 3, 2025 at 09:45:39 AM EST, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
This one has no foam but there¡¯s a white cottony-looking material that is right behind the grille. It looks identical to the Astatic 1011 I have. That mic does have a powered amp, which I run pretty low with my 4 Line sets. It also has a tone control, which I run fully-up so I don¡¯t get muddy audio.?
The 1011 was made to have an amp in it ¡ª the two sliders in the base attest to that.?
The 7077 has never been powered. The work done inside the 7077 was obviously done after manufacture. The workmanship is terrible and everything is black electrical taped together.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sun, Feb 2, 2025 at 19:27, Jim Shorney via groups.io < jimNU0C@...> wrote:
You can find photos of the inside of a 7077 here:
/g/DRAKE-RADIO/album?id=252836
It does have a small transformer in it to step up the voltage output to drive a TR7. No capacitors. And a cheap CB-era dynamic cartridge hidden inside the head. After this many years the blast foam behind the grill will have decayed to crunchy dust. Both the cartridge and the blast foal are easily replaceable.
On Sun, 02 Feb 2025 23:11:59 +0000
"Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote:
> I went on to the 7238 Drake Pre-net this afternoon and strange things were happening. I heard some noise in the speaker when the PTT was pressed and WB0IQK said that I sounded excessively tinny. I was fortunate to have my $10 GE-branded Shure 444, which worked like a charm but, of course, I want to know what is wrong with the 7077, so I took it apart.
>
> Oy, vey! What a mess inside! Someone had put in a couple of capacitors (low value) and what looks like a transformer. It's all kludged in there, so I know this ain't no factory job! Lots of lousy workmanship and electrical tape trying to hold things together!
>
> The mic element I can't be sure if it's correct, though it looks like it all fits together like it should. The mic element measures around 430 ohms on my Fluke 77.
>
> Is this simply a case of the wrong element in this mic? The TR7 manual specifies a high Z mic. I am tempted to simply get a Heil element for high Z and being done with it.
>
> If any of you have a 7077 mic, can you measure resistance across the mic element for me? This should be from ground to pin 1 of the mic plug.
>
> TNX & 73,
>
> Steve Wedge, W1ES
--
73
-Jim
NU0C
|
While we are on the subject of Mics, can someone share the wiring diagram for a powered D104 with me?
On Monday, February 3, 2025 at 09:45:39 AM EST, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
This one has no foam but there¡¯s a white cottony-looking material that is right behind the grille. It looks identical to the Astatic 1011 I have. That mic does have a powered amp, which I run pretty low with my 4 Line sets. It also has a tone control, which I run fully-up so I don¡¯t get muddy audio.?
The 1011 was made to have an amp in it ¡ª the two sliders in the base attest to that.?
The 7077 has never been powered. The work done inside the 7077 was obviously done after manufacture. The workmanship is terrible and everything is black electrical taped together.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sun, Feb 2, 2025 at 19:27, Jim Shorney via groups.io < jimNU0C@...> wrote:
You can find photos of the inside of a 7077 here:
/g/DRAKE-RADIO/album?id=252836
It does have a small transformer in it to step up the voltage output to drive a TR7. No capacitors. And a cheap CB-era dynamic cartridge hidden inside the head. After this many years the blast foam behind the grill will have decayed to crunchy dust. Both the cartridge and the blast foal are easily replaceable.
On Sun, 02 Feb 2025 23:11:59 +0000
"Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote:
> I went on to the 7238 Drake Pre-net this afternoon and strange things were happening. I heard some noise in the speaker when the PTT was pressed and WB0IQK said that I sounded excessively tinny. I was fortunate to have my $10 GE-branded Shure 444, which worked like a charm but, of course, I want to know what is wrong with the 7077, so I took it apart.
>
> Oy, vey! What a mess inside! Someone had put in a couple of capacitors (low value) and what looks like a transformer. It's all kludged in there, so I know this ain't no factory job! Lots of lousy workmanship and electrical tape trying to hold things together!
>
> The mic element I can't be sure if it's correct, though it looks like it all fits together like it should. The mic element measures around 430 ohms on my Fluke 77.
>
> Is this simply a case of the wrong element in this mic? The TR7 manual specifies a high Z mic. I am tempted to simply get a Heil element for high Z and being done with it.
>
> If any of you have a 7077 mic, can you measure resistance across the mic element for me? This should be from ground to pin 1 of the mic plug.
>
> TNX & 73,
>
> Steve Wedge, W1ES
--
73
-Jim
NU0C
|
That was after I changed the mic.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Feb 3, 2025 at 07:09, James Barrie via groups.io < barrie43@...> wrote:
I was there yesterday when you checked in and I didn't notice that your audio sounded tiny.
I did the Heil element in a D104 carcass and had to add a matching transformer to get the impedance up. Probably what they were trying to do on that mic you have, but who knows for sure.? It works great.
73
Jim? ?WA8SDF
? ? FWIW, crystal and ceramic microphone elements look like capacitors.
The load impedance forms a high pass filter with the capacitance. The
higher the impedance the less the bass roll off. There is also an effect
due to the capacitance of the connecting cable, which is in parallel
with the element. If the cable capacitance is too high the level is
depressed since the two act as a capacitive voltage divider. In the bad
old days crystal mics and phonograph pickups were used to feed vacuum
tube grids more or less directly so the load was typically very high,
often several megohms. Crystal elements have the advantage of having
very high output level for a given amount of mechanical driving force
and, if carefully designed, good high frequency response. Because tube
amplifiers were expensive a crystal element could be economical for
cheap phonographs and PA mics. The disadvantages were sensitivity to
high temperatures (much about 90F), sensitivity to mechanical fracture
(scrape a pick up across a record or dropping a mic), high humidity.
There were several arrangements for sealing crystal elements to protect
them from humidity but they were often short lived. Eventually ceramic
elements began to replace crystals. They were much more rugged but had
significantly lower output. For the most part all of these have been
replaced with electret elements of some sort.
? ? ?Up until perhaps the 1970's there were perhaps a dozen makers of
crystal and ceramic phonograph pickups and every maker of microphones
made crystal or ceramic mics. All now completely supplanted by other
mechanisms.
On 2/2/2025 7:36 PM, Jim Shorney via
wrote:
>
> Yes, I am quite aware of the D-104 head characteristics. I'm the guy who posts the attached graph whenever this comes up. For the TR7 470K x 2 is an ideal load for the cartridge with plenty of voltage left to drive the radio. I should think the same would have been true of your Kenwood as well unless it had a not very sensitive mic input. All three of my stands (including the Golden Eagle) are effectively UG stands now. No need to fool around with the active electronics in the T-UGxxx stands. That would be what a friend of mine calls enhanced uselessness. Maybe one of these days I will wire one of the neutered T* stands for my TS-570 and see how the D-104 head likes it. I actually have a D-104/UG around here somewhere that I used with my Tram D-201 back in the day. True high impedance, looking into the grid of a tube.
>
> On Sun, 02 Feb 2025 18:47:27 -0800
> "jerry-KF6VB via
" <jerry=
[email protected]> wrote:
>
>> On 2025-02-02 16:33, Jim Shorney via
wrote:
>>> I have never run any electronics in a D-104/T-UGxx. Just a 470K or
>>> higher resistor in series with the audio line.
>>
>>? ? ?I probably wouldn't have bothered with my TR7 - I would have just
>> connected the D104 to that pin with the 470K resistor.? This was in
>> the mid-80's, and I wanted to hook it up to my TS-830S.? I don't
>> think that radio had a high impedance input.? I seem to remember
>> 50K or so.? But that was many years ago.
>>
>> The 20 megohms that the JFET presents to the Rochelle salts element
>> maximizes its bass response.
>>
>>? ? ? ? ? ? ? ? ? ? ? ? ? - Jerry, KF6VB
>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
This one has no foam but there¡¯s a white cottony-looking material that is right behind the grille. It looks identical to the Astatic 1011 I have. That mic does have a powered amp, which I run pretty low with my 4 Line sets. It also has a tone control, which I run fully-up so I don¡¯t get muddy audio.?
The 1011 was made to have an amp in it ¡ª the two sliders in the base attest to that.?
The 7077 has never been powered. The work done inside the 7077 was obviously done after manufacture. The workmanship is terrible and everything is black electrical taped together.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sun, Feb 2, 2025 at 19:27, Jim Shorney via groups.io < jimNU0C@...> wrote:
You can find photos of the inside of a 7077 here:
/g/DRAKE-RADIO/album?id=252836
It does have a small transformer in it to step up the voltage output to drive a TR7. No capacitors. And a cheap CB-era dynamic cartridge hidden inside the head. After this many years the blast foam behind the grill will have decayed to crunchy dust. Both the cartridge and the blast foal are easily replaceable.
On Sun, 02 Feb 2025 23:11:59 +0000
"Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote:
> I went on to the 7238 Drake Pre-net this afternoon and strange things were happening. I heard some noise in the speaker when the PTT was pressed and WB0IQK said that I sounded excessively tinny. I was fortunate to have my $10 GE-branded Shure 444, which worked like a charm but, of course, I want to know what is wrong with the 7077, so I took it apart.
>
> Oy, vey! What a mess inside! Someone had put in a couple of capacitors (low value) and what looks like a transformer. It's all kludged in there, so I know this ain't no factory job! Lots of lousy workmanship and electrical tape trying to hold things together!
>
> The mic element I can't be sure if it's correct, though it looks like it all fits together like it should. The mic element measures around 430 ohms on my Fluke 77.
>
> Is this simply a case of the wrong element in this mic? The TR7 manual specifies a high Z mic. I am tempted to simply get a Heil element for high Z and being done with it.
>
> If any of you have a 7077 mic, can you measure resistance across the mic element for me? This should be from ground to pin 1 of the mic plug.
>
> TNX & 73,
>
> Steve Wedge, W1ES
--
73
-Jim
NU0C
|
This is a 7077. Made by Astatic, rather than Turner.?
If there are no components in series with the element, then you should be able to get a reading from pin 1 to GND. One may need to press the PTT if the PTT shuts off connection to the element.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sun, Feb 2, 2025 at 18:57, Craig W8CS via groups.io < craig_severson@...> wrote:
I have a 7075; tried to get a resistance measurement that was not the PTT closure and every combination was open circuit. Don't have a schematic so I was fumbling in the dark.?
--
Craig/W8CS
Greenville, SC
|
It has 3 wires. I suspect that there¡¯s a common in there.?
I did think that perhaps this could be a filter but the capacitors are 0.01 and 0.47, which seem like coupling caps. They¡¯re also in series with the transformer.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sun, Feb 2, 2025 at 18:57, Richard Knoppow via groups.io < 1oldlens1@...> wrote: It sounds like someone may have added a filter to the mic. Can you
tell if the transformer is open? Is is actually a choke?
On 2/2/2025 3:46 PM, Steve Wedge, W1ES/4 via groups.io wrote:
> This came with my first TR7, which I bought in 2019 from a ham. The mic
> worked fine until today.
>
> It¡¯s still a head-scratcher¡
>
> Steve Wedge, W1ES
>
> Time flies like an arrow. Fruit flies like a banana.
>
>
> Sent from Proton Mail <https://proton.me/mail/home> for iOS
>
>
> On Sun, Feb 2, 2025 at 18:37, jerry-KF6VB <jerry@... <mailto:On Sun,
> Feb 2, 2025 at 18:37, jerry-KF6VB <<a href=>> wrote:
>> Sounds like something a CBer might do to get more audio grunt.
>>
>> - Jerry, KF6VB
>>
>>
>> On 2025-02-02 15:35, Steve Wedge, W1ES/4 via groups.io wrote:
>> > It is looking like I¡¯ll need to do that. The current element fits
>> > but there are series capacitors and that tiny transformer. These
>> > components seem to be good (capacitors are dead-on).
>> >
>> > I was shocked to see all that stuff added in there (and with such poor
>> > workmanship).
>> >
>> > Just a straight element would simplify everything and I can rip all
>> > the other stuff out.
>> >
>> > 73,
>> >
>> > Steve Wedge, W1ES
>> >
>> > Time flies like an arrow. Fruit flies like a banana.
>> >
>> > Sent from Proton Mail [1] for iOS
>> >
>> > On Sun, Feb 2, 2025 at 18:15, KB9VY via groups.io
>> > <lcoblentz3@...> wrote:
>> >
>> >> I put the Heil element in mine. Works great now.
>> >>
>> >> Larry - KB9VY
>> >>
>> >> Sent from Proton Mail [1] for iOS
>> >>
>> >> On Sun, Feb 2, 2025 at 18:11, Steve Wedge, W1ES/4 via groups.io <
>> >> w1es@... [2]> wrote:
>> >>
>> >>> Hi, gang!
>> >>>
>> >>> I went on to the 7238 Drake Pre-net this afternoon and strange
>> >>> things were happening. I heard some noise in the speaker when the
>> >>> PTT was pressed and WB0IQK said that I sounded excessively tinny.
>> >>> I was fortunate to have my $10 GE-branded Shure 444, which worked
>> >>> like a charm but, of course, I want to know what is wrong with the
>> >>> 7077, so I took it apart.
>> >>>
>> >>> Oy, vey! What a mess inside! Someone had put in a couple of
>> >>> capacitors (low value) and what looks like a transformer. It's
>> >>> all kludged in there, so I know this ain't no factory job! Lots
>> >>> of lousy workmanship and electrical tape trying to hold things
>> >>> together!
>> >>>
>> >>> The mic element I can't be sure if it's correct, though it looks
>> >>> like it all fits together like it should. The mic element
>> >>> measures around 430 ohms on my Fluke 77.
>> >>>
>> >>> Is this simply a case of the wrong element in this mic? The TR7
>> >>> manual specifies a high Z mic. I am tempted to simply get a Heil
>> >>> element for high Z and being done with it.
>> >>>
>> >>> If any of you have a 7077 mic, can you measure resistance across
>> >>> the mic element for me? This should be from ground to pin 1 of
>> >>> the mic plug.
>> >>>
>> >>> TNX & 73,
>> >>>
>> >>> Steve Wedge, W1ES
>> >>>
>> >>> Time flies like an arrow. Fruit flies like a banana.
>> >>>
>> >>> Sent with Proton Mail [1] secure email.
>> >
>> >
>> >
>> > Links:
>> > ------
>> > [1] https://proton.me/mail/home
>> > [2] http://www.jm-properties.com/class=
>> > [3] /g/DRAKE-RADIO/message/82474
>> > [4] /mt/110961661/243852
>> > [5] /g/DRAKE-RADIO/post
>> > [6] /g/DRAKE-RADIO/editsub/243852
>> > [7]
>> > /g/DRAKE-RADIO/leave/12260778/243852/767576506/xyzzy
>>
>>
>>
>>
>>
>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: Drake T-4XB rubber feet
One might have to be cautious with those small feet with the embedded studs. ?In virtually all of the ones I have seen, that stud has started to protrude through the bottom of the foot with just a very thin amount of rubber on the tip. ?Not sure if that will mar a soft pine desk surface or not. ?I always pitched them and replaced them with better feet.
Those small rubber feet with embedded 6-32 studs are, as you note, used on the AC-4 Power Supply, and elsewhere. They are called out in the mounting options shown in the TR-4 series manuals as one of the options for table-top installation.?
?
Now for a bit of trivia. Those small feet were standard equipment on my Drake AC-10 Power Supply that I still have. It powered the Drake TR-22C 2M Transceiver and AA-10 Amplifier.? that I no longer have in my inventory. They are also the rear feet on my Drake L7 Linear Amplifier. I always thought they were too small for that duty, but they have been there since 1982 when I bought the L7 brand new. I suspect more uses as well that I just never noticed. The little embedded stud feet are quite handy and are generally available at an industrial hardware store, McMaster Carr, Nationwide Radio, and likely elsewhere.?
?
73,
-Bill Shadid, W9MXQ
|
Re: Drake T-4XB rubber feet
>¡±Those small rubber feet with embedded 6-32 studs are, as you note, used on the AC-4 Power Supply, and elsewhere.¡± ? For the curious or those who have missing threaded bumpers, here¡¯s the McMaster-Carr information: ? ? Item No.: ?9541K8 ? $10.84 USD + shipping for a package of 25 bumpers. ? Paul, W9AC://www.mcmaster.com/products/rubber-bumpers/bumpers~/threaded-stud-bumpers~~/
|
Unloading the D104 cartridge makes more sense as the lower transmit passband width is extended.? For transceivers with a conventional 300 Hz to 2.4 kHz transmit bandwidth, the low-end response is restricted by the SSB crystal or mechanical transmit filter.? Adjusting the carrier set point to allow an increased low-end response only robs articulation at the upper end.?
?
As Jim points out, 470K in series with the cartridge is a reasonable value for bandwidth-limited transmitters.? Interestingly, the input Z of Astatic's 2-transistor circuit (i.e., T-UG8 stand), also computes to approximately 470K.??
?
For typical AM and ESSB transmit bandwidths, the JFET transformer can extend the response to below 100 Hz.? There's no reason to extend below about 75 Hz.? That's the lowest fundamental I've measured using FFT software from Charlie Van Dyke's voice, a well-known voice-over talent.? Anything measured lower, is the result of non-voice factors like vibration, rumble, and breath sounds.??
?
Paul, W9AC
|
Re: Drake T-4XB rubber feet
Those small rubber feet with embedded 6-32 studs are, as you note, used on the AC-4 Power Supply, and elsewhere. They are called out in the mounting options shown in the TR-4 series manuals as one of the options for table-top installation.?
?
Now for a bit of trivia. Those small feet were standard equipment on my Drake AC-10 Power Supply that I still have. It powered the Drake TR-22C 2M Transceiver and AA-10 Amplifier.? that I no longer have in my inventory. They are also the rear feet on my Drake L7 Linear Amplifier. I always thought they were too small for that duty, but they have been there since 1982 when I bought the L7 brand new. I suspect more uses as well that I just never noticed. The little embedded stud feet are quite handy and are generally available at an industrial hardware store, McMaster Carr, Nationwide Radio, and likely elsewhere.?
?
73,
-Bill Shadid, W9MXQ
|
I was there yesterday when you checked in and I didn't notice that your audio sounded tiny.
I did the Heil element in a D104 carcass and had to add a matching transformer to get the impedance up. Probably what they were trying to do on that mic you have, but who knows for sure.? It works great. 73 Jim? ?WA8SDF
? ? FWIW, crystal and ceramic microphone elements look like capacitors.
The load impedance forms a high pass filter with the capacitance. The
higher the impedance the less the bass roll off. There is also an effect
due to the capacitance of the connecting cable, which is in parallel
with the element. If the cable capacitance is too high the level is
depressed since the two act as a capacitive voltage divider. In the bad
old days crystal mics and phonograph pickups were used to feed vacuum
tube grids more or less directly so the load was typically very high,
often several megohms. Crystal elements have the advantage of having
very high output level for a given amount of mechanical driving force
and, if carefully designed, good high frequency response. Because tube
amplifiers were expensive a crystal element could be economical for
cheap phonographs and PA mics. The disadvantages were sensitivity to
high temperatures (much about 90F), sensitivity to mechanical fracture
(scrape a pick up across a record or dropping a mic), high humidity.
There were several arrangements for sealing crystal elements to protect
them from humidity but they were often short lived. Eventually ceramic
elements began to replace crystals. They were much more rugged but had
significantly lower output. For the most part all of these have been
replaced with electret elements of some sort.
? ? ?Up until perhaps the 1970's there were perhaps a dozen makers of
crystal and ceramic phonograph pickups and every maker of microphones
made crystal or ceramic mics. All now completely supplanted by other
mechanisms.
On 2/2/2025 7:36 PM, Jim Shorney via wrote:
>
> Yes, I am quite aware of the D-104 head characteristics. I'm the guy who posts the attached graph whenever this comes up. For the TR7 470K x 2 is an ideal load for the cartridge with plenty of voltage left to drive the radio. I should think the same would have been true of your Kenwood as well unless it had a not very sensitive mic input. All three of my stands (including the Golden Eagle) are effectively UG stands now. No need to fool around with the active electronics in the T-UGxxx stands. That would be what a friend of mine calls enhanced uselessness. Maybe one of these days I will wire one of the neutered T* stands for my TS-570 and see how the D-104 head likes it. I actually have a D-104/UG around here somewhere that I used with my Tram D-201 back in the day. True high impedance, looking into the grid of a tube.
>
> On Sun, 02 Feb 2025 18:47:27 -0800
> "jerry-KF6VB via " <jerry=[email protected]> wrote:
>
>> On 2025-02-02 16:33, Jim Shorney via wrote:
>>> I have never run any electronics in a D-104/T-UGxx. Just a 470K or
>>> higher resistor in series with the audio line.
>>
>>? ? ?I probably wouldn't have bothered with my TR7 - I would have just
>> connected the D104 to that pin with the 470K resistor.? This was in
>> the mid-80's, and I wanted to hook it up to my TS-830S.? I don't
>> think that radio had a high impedance input.? I seem to remember
>> 50K or so.? But that was many years ago.
>>
>> The 20 megohms that the JFET presents to the Rochelle salts element
>> maximizes its bass response.
>>
>>? ? ? ? ? ? ? ? ? ? ? ? ? - Jerry, KF6VB
>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
FWIW, crystal and ceramic microphone elements look like capacitors. The load impedance forms a high pass filter with the capacitance. The higher the impedance the less the bass roll off. There is also an effect due to the capacitance of the connecting cable, which is in parallel with the element. If the cable capacitance is too high the level is depressed since the two act as a capacitive voltage divider. In the bad old days crystal mics and phonograph pickups were used to feed vacuum tube grids more or less directly so the load was typically very high, often several megohms. Crystal elements have the advantage of having very high output level for a given amount of mechanical driving force and, if carefully designed, good high frequency response. Because tube amplifiers were expensive a crystal element could be economical for cheap phonographs and PA mics. The disadvantages were sensitivity to high temperatures (much about 90F), sensitivity to mechanical fracture (scrape a pick up across a record or dropping a mic), high humidity. There were several arrangements for sealing crystal elements to protect them from humidity but they were often short lived. Eventually ceramic elements began to replace crystals. They were much more rugged but had significantly lower output. For the most part all of these have been replaced with electret elements of some sort.
Up until perhaps the 1970's there were perhaps a dozen makers of crystal and ceramic phonograph pickups and every maker of microphones made crystal or ceramic mics. All now completely supplanted by other mechanisms.
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On 2/2/2025 7:36 PM, Jim Shorney via groups.io wrote: Yes, I am quite aware of the D-104 head characteristics. I'm the guy who posts the attached graph whenever this comes up. For the TR7 470K x 2 is an ideal load for the cartridge with plenty of voltage left to drive the radio. I should think the same would have been true of your Kenwood as well unless it had a not very sensitive mic input. All three of my stands (including the Golden Eagle) are effectively UG stands now. No need to fool around with the active electronics in the T-UGxxx stands. That would be what a friend of mine calls enhanced uselessness. Maybe one of these days I will wire one of the neutered T* stands for my TS-570 and see how the D-104 head likes it. I actually have a D-104/UG around here somewhere that I used with my Tram D-201 back in the day. True high impedance, looking into the grid of a tube.
On Sun, 02 Feb 2025 18:47:27 -0800
"jerry-KF6VB via groups.io" <jerry@...> wrote:
On 2025-02-02 16:33, Jim Shorney via groups.io wrote:
I have never run any electronics in a D-104/T-UGxx. Just a 470K or
higher resistor in series with the audio line. I probably wouldn't have bothered with my TR7 - I would have just
connected the D104 to that pin with the 470K resistor. This was in
the mid-80's, and I wanted to hook it up to my TS-830S. I don't
think that radio had a high impedance input. I seem to remember
50K or so. But that was many years ago.
The 20 megohms that the JFET presents to the Rochelle salts element
maximizes its bass response.
- Jerry, KF6VB
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Yes, I am quite aware of the D-104 head characteristics. I'm the guy who posts the attached graph whenever this comes up. For the TR7 470K x 2 is an ideal load for the cartridge with plenty of voltage left to drive the radio. I should think the same would have been true of your Kenwood as well unless it had a not very sensitive mic input. All three of my stands (including the Golden Eagle) are effectively UG stands now. No need to fool around with the active electronics in the T-UGxxx stands. That would be what a friend of mine calls enhanced uselessness. Maybe one of these days I will wire one of the neutered T* stands for my TS-570 and see how the D-104 head likes it. I actually have a D-104/UG around here somewhere that I used with my Tram D-201 back in the day. True high impedance, looking into the grid of a tube. On Sun, 02 Feb 2025 18:47:27 -0800 "jerry-KF6VB via groups.io" <jerry@...> wrote: On 2025-02-02 16:33, Jim Shorney via groups.io wrote:
I have never run any electronics in a D-104/T-UGxx. Just a 470K or
higher resistor in series with the audio line. I probably wouldn't have bothered with my TR7 - I would have just
connected the D104 to that pin with the 470K resistor. This was in
the mid-80's, and I wanted to hook it up to my TS-830S. I don't
think that radio had a high impedance input. I seem to remember
50K or so. But that was many years ago.
The 20 megohms that the JFET presents to the Rochelle salts element
maximizes its bass response.
- Jerry, KF6VB -- 73 -Jim NU0C
|
Paul Christensen
Jim Shorney
