Jay, I just took a look at the schematic and didn't see anything that would currently be unavailable except maybe the coils and possibly the socket for the blanker. What is specifically wrong with it? Is it physical damage or electrically not functioning?
?
Dave
|
I looked into the PA I damaged when a faulty key put the radio in transmit: - One of the parasitic choke leads popped out of the resistor.
- One of the 1-watt cathode resistors is cracked and both read higher than 15 ohms.
- No more than 75mA when tuning.
I'm thinking of replacing the 6GE5s; both cathode resistors with 2-watt film resistors; both parasitic chokes; possibly replacing the 12BY7 driver tube.
Appreciate any expert advice on where else to check and what else to replace.
Thanks & 73 Jay W6CJ
|
Looks like reasonable stuff. Will have the advantage over fiberglas that it won't get into your fingers. Fiberlas should be handled with fairly heavy gloves and a dust mask. Most hardware stores have it. I usually use the pink colored stuff for speaker boxes.
Small boxes can be filled with it but large boxes just need to be lined (to maybe two inches thick) to reduce internal reflections and resulting resonances.
BTW, speaker cabinet walls should be very stiff. Don't use particle board, which is heavy but not stiff, high quality plywood is superior. For large cabinets it should be well-braced with the braces at odd spacing so as to break up the surfaces to avoid re-inforcing resonances.
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On 1/2/2025 11:22 AM, n4buq wrote: Is this the same product?
quantity=1 < Bag-260-317?quantity=1>
Barry - N4BUQ
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
I have commented in this and other lists about the speakers sold for communication receivers. I won't repeat everything here. The technology to make a better speaker is not new in any way and can be quite simple. The receiver does not need a high fidelity speaker and one would be a mistake. The range of interest is pretty limited. However, what does matter is the resonances caused by the small open-back box, as you point out. If you mount a "50c" speaker in a decent box you will be amazed at how much better it sounds. For a small speaker, like the one in the MS-4, perhaps half a cubic foot of volume is enough. Easy to make from a minimum of 1/4" plywood. Fill with sound absorbent, insulating fiberglas will do quite nicely. Does not need a port. These small speakers usually have reasonably good response up through the speech range and don't need a lot of low response. Get rid of the resonances caused by the too small enclosure and the mechanical resonances of the un-damped cabinet material.
Note that the audio amplifiers in vacuum tube receivers usually have starved transformers and are marginal in power. A simple pentode power amp usually has a substantial amount of intermodulation distortion as well as harmonic distortion. The I.M. is usually a property of the tube itself, some are better than others. Negative feedback will reduce both kinds of distortion but at the price of needing increased gain somewhere to compensate for the feedback. I can think of only a couple of single ended pentode amps that employed it (RCA AR-88 is an example).
While the audio frequency range and dynamic range of communication receivers is not great the distortion at even fairly low levels, well under a watt, are significant. The effect on both phone and CW are very noticeable. On CW the effect is to magnify the effect of noise and interference. If one connects a high quality amp to the detector output and compares it to the normal output you will hear a distinctive difference, not too subtle. Some old receivers, such as the old Super-Pro and SX-28, had push pull amps which at least reduced the harmonic distortion (don't do anything for I.M.) and the difference in sound between those and the common single-ended amps is very noticeable.
At least one can improve the speaker cabinet rather cheaply.
I certainly agree about the MS-4 cabinet with a power supply taking up almost all the interior volume. Bad for sound but practical and economical, so it was done. The idea that audio quality does not matter in communications is an easy mistake to make, narrow band and does distortion count (you bet it does). A better speaker in a better enclosure will make a difference but just improving the enclosure will surprise you.
I will also point out that even in broadcast receivers, where audio quality was a sales point, the usual arrangement was an open back cabinet with, perhaps, some peaking at around 90Hz to give the illusion of bass.
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On 1/2/2025 7:41 AM, Paul Christensen via groups.io wrote: >’Bob Heil got that part right.? "It's no more than a 50 cent
speaker....in a $50.00? box".’
I don’t think the issue is so much the MS4 speaker cone or magnet. There’s essentially no baffle distance at even moderately low frequencies between the front and back of the cone.? ?That means the forward cone wave short circuits the back wave at those frequencies. And by moderate, I don’t mean Hi-Fi in any way; that requires even more baffle distance or a fully enclosed “infinite baffle.”
I’ve closed the back of mine with cardboard and that helps to create a fuller sound from the MS4.? Back in the day, manufacturers that offered speakers as accessories to the main product line put no effort into understanding the effect of baffling.
Paul, W9AC
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
I have a 4NB noise blanker that Ron, WB4HFN said he was unable to repair due to parts availability.? Is there anyone who repairs them??? Thanks & 73 Jay W6CJ
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Yup…One and the same, albeit a wee (sic) bit cheaper at your store
Joe – W7RKN ? ? Is this the same product?
|
Is this the same product?
Barry - N4BUQ
I stuffed both of my Drake speaker boxes with speaker ‘wool’ found at Amazon.? (Acousta-Stuf Polyfill Speaker Cabinet Sound Damping Material 1 lb. Bag)? Worked very well.? A little pricy, but, isn’t most ham goodies thus found??!!? J ? Joe – W7RKN ? ? ? >’Bob Heil got that part right.? "It's no more than a 50 cent speaker....in a $50.00? box".’ ? I don’t think the issue is so much the MS4 speaker cone or magnet.? There’s essentially no baffle distance at even moderately low frequencies between the front and back of the cone.? ?That means the forward cone wave short circuits the back wave at those frequencies.? And by moderate, I don’t mean Hi-Fi in any way; that requires even more baffle distance or a fully enclosed “infinite baffle.”? ? I’ve closed the back of mine with cardboard and that helps to create a fuller sound from the MS4.? Back in the day, manufacturers that offered speakers as accessories to the main product line put no effort into understanding the effect of baffling.? ?
|
I stuffed both of my Drake speaker boxes with speaker ‘wool’ found at Amazon.? (Acousta-Stuf Polyfill Speaker Cabinet Sound Damping Material 1 lb. Bag)? Worked very well.? A little pricy, but, isn’t most ham goodies thus found??!!? J ? Joe – W7RKN ? ? ? >’Bob Heil got that part right.? "It's no more than a 50 cent speaker....in a $50.00? box".’ ? I don’t think the issue is so much the MS4 speaker cone or magnet.? There’s essentially no baffle distance at even moderately low frequencies between the front and back of the cone.? ?That means the forward cone wave short circuits the back wave at those frequencies.? And by moderate, I don’t mean Hi-Fi in any way; that requires even more baffle distance or a fully enclosed “infinite baffle.”? ? I’ve closed the back of mine with cardboard and that helps to create a fuller sound from the MS4.? Back in the day, manufacturers that offered speakers as accessories to the main product line put no effort into understanding the effect of baffling.? ?
|
I thought that the AF pot didn't go all the way to zero.? Back in the day, it would have been easy to sub a different pot set.
I like the idea of the RF gain and can't for the life of me understand why I didn't think of that.? I got my ticket in 1982, so the days of most hams "riding the RF gain" were long past and I have my RF gain almost always set to max.? Drake, to a certain extent, also went this way by the C Line (though the TR3/4 was set up the same way) by putting the RF gain on the puny little metal control concentric to the AF gain knob.
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Thursday, January 2nd, 2025 at 1:25 PM, kg9hfrank@... via groups.io <kg9hfrank@...> wrote:
Jerry, When I sold potentiometers with Stackpole Carbon Company, that issue is specified as “hop-off” and specified as a percentage of the resistance.When we sold them to Heath, Electrovoice, Zenith, etc., ?the engineer needed to specify a percentage of hop-off or nothing”. The hop-off actually protected the potentiometer so you never dialed in a zero with current flowing through the resistive area.
? ? ?Frank Krozel ? ? ? ? ? ?KG9H Life Member, ARRL ? ? (630) 924-1600 kg9hfrank@...
On Jan 2, 2025, at 12:14?PM, jerry-KF6VB via groups.io <jerry@...> wrote:
One minor audio annoyance with the TR7 - the volume control doesn't go all the way to zero. Instead of a tradition voltage divider pot, they do something with the AGC. ?So to get the thing to quiet down, I also turn down the RF gain. ????????????????- Jerry, KF6VB On 2025-01-01 08:06, Jim Shorney via groups.io wrote: FWIW the TR7 uses an LM380. It works pretty well.
On Wed, 1 Jan 2025 10:45:24 -0500
"Mike Bryce via groups.io" <prosolar@...> wrote:
FYI… I designed an audio amp board for the R4C that used a LM380. Worked great and had plenty of humph to drive the MS4 speaker to room filling volume
--
73
-Jim
NU0C
|
Jerry, When I sold potentiometers with Stackpole Carbon Company, that issue is specified as “hop-off” and specified as a percentage of the resistance. When we sold them to Heath, Electrovoice, Zenith, etc., ?the engineer needed to specify a percentage of hop-off or nothing”. The hop-off actually protected the potentiometer so you never dialed in a zero with current flowing through the resistive area.
? ? ?Frank Krozel ? ? ? ? ? ?KG9H Life Member, ARRL ? ? (630) 924-1600 kg9hfrank@...
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On Jan 2, 2025, at 12:14?PM, jerry-KF6VB via groups.io <jerry@...> wrote:
One minor audio annoyance with the TR7 - the volume control doesn't go all the way to zero. Instead of a tradition voltage divider pot, they do something with the AGC. ?So to get the thing to quiet down, I also turn down the RF gain. ????????????????- Jerry, KF6VB On 2025-01-01 08:06, Jim Shorney via groups.io wrote: FWIW the TR7 uses an LM380. It works pretty well.
On Wed, 1 Jan 2025 10:45:24 -0500
"Mike Bryce via groups.io" <prosolar@...> wrote:
FYI… I designed an audio amp board for the R4C that used a LM380. Worked great and had plenty of humph to drive the MS4 speaker to room filling volume
--
73
-Jim
NU0C
|
One minor audio annoyance with the TR7 - the volume control doesn't go all the way to zero.
Instead of a tradition voltage divider pot, they do something with the AGC. So to get
the thing to quiet down, I also turn down the RF gain.
- Jerry, KF6VB
toggle quoted message
Show quoted text
On 2025-01-01 08:06, Jim Shorney via groups.io wrote: FWIW the TR7 uses an LM380. It works pretty well.
On Wed, 1 Jan 2025 10:45:24 -0500
"Mike Bryce via groups.io" <prosolar@...> wrote:
FYI… I designed an audio amp board for the R4C that used a LM380. Worked great and had plenty of humph to drive the MS4 speaker to room filling volume --
73
-Jim
NU0C
|
Re: T-4XC has a "condition"
Barry...indeed, check for correct idling current with zero drive. Adjust it using the bias control on the AC-4 power supply.? You are aiming for about 70 mA (the "tick mark").
Also.....practice tuning up into a known good 50 Ohm load rated at 150w or better with known good cables first.? Dump the "tuner" for now.? I would put a wattmeter inline to the 50 ohm load if you have one,?rather than trying to use the internal relative output meter.? That way there are fewer buttons to "mess" with until you are comfortable with the tune-up process.
And if you are pinning the ammeter...STOP right away, as something is wrong!? Back off the drive and try again.
73 and GL
Peter VE7PS
How have you set your bias. That’s the first step. Pinned to the right is not a condition you want to be in for long so I would suggest not tuning up until you figure it out.? I would verify that you have appropriate and steady bias current first.
On Thursday, January 2, 2025 at 10:01:40 AM CST, Dean N2TNN via <n2tnn= [email protected]> wrote:
GM all and HNY
?
I have a T-4XC in great condition but is not acting normal. It puts out 110 watts, sounds great on CW and cooperates with my straight key. Unknown about the SSB side because I never used it.
?
This is difficult to express because I don't really know what I am talking about so here goes. Tuning the rig on different bands takes forever to get it right. I have watched videos and it looks easy. I follow the instructions in the manual and it never is the same.
?
All controls are set CCW. I then turn up the gain control slowly, maybe 1/4 the way and the needle pins to the right. Once it is pinned I can never get it to dip when I adjust the plate knob.
?
So what I do next is to fool with the controls to get max power out with the lowest SWR on the tuner. With the load knob adjusted for output the needle is still pinned. When I push it in the needle moves down to about .300
?
Also, after tuning up with the "tune" setting I go to CW and when I key down I have to fine tune all the settings again.
?
I really like this rig and want to use it but something is not right. Any suggestions?
?
Dean/ N2TNN
|
Re: T-4XC has a "condition"
I have seen loss of bias not only with a failed capacitor in the bias supply but also with dirty contacts in the Jones connector from the AC-4 to the transmitter.? DeOxIt is a good cleaner for this.? Apply to the blades on the back of the rig and plug/unplug a few times.
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Thursday, January 2nd, 2025 at 12:19 PM, Barry KJ5GQM via groups.io <chasbg@...> wrote:
How have you set your bias. That’s the first step. Pinned to the right is not a condition you want to be in for long so I would suggest not tuning up until you figure it out. ?I would verify that you have appropriate and steady bias current first.
On Thursday, January 2, 2025 at 10:01:40 AM CST, Dean N2TNN via groups.io <n2tnn@...> wrote:
GM all and HNY
?
I have a T-4XC in great condition but is not acting normal. It puts out 110 watts, sounds great on CW and cooperates with my straight key. Unknown about the SSB side because I never used it.
?
This is difficult to express because I don't really know what I am talking about so here goes. Tuning the rig on different bands takes forever to get it right. I have watched videos and it looks easy. I follow the instructions in the manual and it never is the same.
?
All controls are set CCW. I then turn up the gain control slowly, maybe 1/4 the way and the needle pins to the right. Once it is pinned I can never get it to dip when I adjust the plate knob.
?
So what I do next is to fool with the controls to get max power out with the lowest SWR on the tuner. With the load knob adjusted for output the needle is still pinned. When I push it in the needle moves down to about .300
?
Also, after tuning up with the "tune" setting I go to CW and when I key down I have to fine tune all the settings again.
?
I really like this rig and want to use it but something is not right. Any suggestions?
?
Dean/ N2TNN
|
Re: T-4XC has a "condition"
How have you set your bias. That’s the first step. Pinned to the right is not a condition you want to be in for long so I would suggest not tuning up until you figure it out. ?I would verify that you have appropriate and steady bias current first.
On Thursday, January 2, 2025 at 10:01:40 AM CST, Dean N2TNN via groups.io <n2tnn@...> wrote:
GM all and HNY
?
I have a T-4XC in great condition but is not acting normal. It puts out 110 watts, sounds great on CW and cooperates with my straight key. Unknown about the SSB side because I never used it.
?
This is difficult to express because I don't really know what I am talking about so here goes. Tuning the rig on different bands takes forever to get it right. I have watched videos and it looks easy. I follow the instructions in the manual and it never is the same.
?
All controls are set CCW. I then turn up the gain control slowly, maybe 1/4 the way and the needle pins to the right. Once it is pinned I can never get it to dip when I adjust the plate knob.
?
So what I do next is to fool with the controls to get max power out with the lowest SWR on the tuner. With the load knob adjusted for output the needle is still pinned. When I push it in the needle moves down to about .300
?
Also, after tuning up with the "tune" setting I go to CW and when I key down I have to fine tune all the settings again.
?
I really like this rig and want to use it but something is not right. Any suggestions?
?
Dean/ N2TNN
|
Re: R4C Sherwood audio mod questions
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Hi
Floyd,
?
My
most recent post of the AMP-4 information was yesterday at
1:37 PM MST.
?
For
everyone’s convenience, attached to this email are PDFs for
the following:
AMP-4,
FC-4, MIX-4, PD-4, RPS-4 and the FPS-4 and alignment tips
document.
If
there is a document repository location associated with this
email reflector, would someone please deposit these 6
documents there.
?
Rob,
NC0B
?
?
Hi Rob.? Where did you post that stuff??
I've looked here in files and photos, at your website and on
Mods.dk with no luck.
|
Re: R4C Sherwood audio mod questions
Hi Floyd,
?
My most recent post of the AMP-4 information was yesterday at 1:37 PM MST.
?
For everyone’s convenience, attached to this email are PDFs for the following:
AMP-4, FC-4, MIX-4, PD-4, RPS-4 and the FPS-4 and alignment tips document.
If there is a document repository location associated with this email reflector, would someone please deposit these 6 documents there.
?
Rob,
NC0B
?
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From: [email protected] [mailto:[email protected]]
On Behalf Of Floyd - K8AC via groups.io
Sent: Thursday, January 02, 2025 9:24 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C Sherwood audio mod questions
?
Hi Rob.? Where did you post that stuff?? I've looked here in files and photos, at your website and on Mods.dk with no luck.
|
Re: R4C Sherwood audio mod questions
Hi Rob.? Where did you post that stuff?? I've looked here in files and photos, at your website and on Mods.dk with no luck.
?
73, Floyd
|
GM all and HNY
?
I have a T-4XC in great condition but is not acting normal. It puts out 110 watts, sounds great on CW and cooperates with my straight key. Unknown about the SSB side because I never used it.
?
This is difficult to express because I don't really know what I am talking about so here goes. Tuning the rig on different bands takes forever to get it right. I have watched videos and it looks easy. I follow the instructions in the manual and it never is the same.
?
All controls are set CCW. I then turn up the gain control slowly, maybe 1/4 the way and the needle pins to the right. Once it is pinned I can never get it to dip when I adjust the plate knob.
?
So what I do next is to fool with the controls to get max power out with the lowest SWR on the tuner. With the load knob adjusted for output the needle is still pinned. When I push it in the needle moves down to about .300
?
Also, after tuning up with the "tune" setting I go to CW and when I key down I have to fine tune all the settings again.
?
I really like this rig and want to use it but something is not right. Any suggestions?
?
Dean/ N2TNN
|
Re: R4C Sherwood audio mod questions
Floyd,
I posted the AMP-4 instructions again yesterday. Includes the schematic.?
Rob, NC0B?
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On Jan 2, 2025, at 8:33?AM, Floyd - K8AC via groups.io <floydsense@...> wrote:
?
I've been looking over documentation I've assembled on the Sherwood audio stage modification.? I have diagrams from the April 1979 HR article, from MODS.dk and from the files section here.? Since none of these except for the HR article are dated, I'm unsure
which is the latest improvement.? Hopefully someone can point me in the right direction.? Apparently after the HR article, there were changes made as follows but I couldn't find an explanation for the changes: 1. The .22 cap and 1500 resistor on the input
were eliminated, 2. The 200 uF cap on pin 2 was changed to 400 uF, the 390 ohm resistor was changed to 270 ohms.? Which version of the circuit is the best one to use?
?
73, Floyd - K8AC
|
>’Bob Heil got that part right.? "It's no more than a 50 cent speaker....in a $50.00? box".’ ? I don’t think the issue is so much the MS4 speaker cone or magnet.? There’s essentially no baffle distance at even moderately low frequencies between the front and back of the cone.? ?That means the forward cone wave short circuits the back wave at those frequencies.? And by moderate, I don’t mean Hi-Fi in any way; that requires even more baffle distance or a fully enclosed “infinite baffle.”? ? I’ve closed the back of mine with cardboard and that helps to create a fuller sound from the MS4.? Back in the day, manufacturers that offered speakers as accessories to the main product line put no effort into understanding the effect of baffling.? ? ? Paul, W9AC
|
Jay W6CJ
Rob Sherwood
Floyd - K8AC
Paul Christensen