Hi Joseph,
?
Initially I duplicated the low frequency roll-off of the stock amp, but later changed the input roll-off to be minimal.? I see a typo in the attached schematic.
The output coupling electrolytic C1 should say 330 uF not us.? That is likely the dominant cause of low frequency roll-off. ?The 330 uF could be increased to 470 uF or even 1000 uF, but I don¡¯t know whether an MS-4 speaker would produce any additional low
frequency audio.? Headphones would be a different matter.? I doubt there is any need to increase C2 in the feedback circuit, but I have never experimented with trying to extend the low end.?
?
I happen to use Icom SP-20 speakers on all my rigs, and while it reproduces 150 Hz quite well, it is really falling off at 100 Hz.
?
Rob, NC0B
?
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Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Joseph K7CBR via groups.io
Sent: Wednesday, January 01, 2025 11:32 AM
To: [email protected]
Subject: [DRAKE-RADIO] AMP-4
?
Mr. Rob... Can you please remind me what the low frequency attenuation was for your AMP-4? Thanks!
On Wednesday, January 1, 2025 at 12:59:27 PM EST, Rob Sherwood via groups.io <rob@...> wrote:
My AMP-4 feedback loop was designed for about a 3 dB roll-off at 3 kHz.? Personal choice.? Rob, NC0B
> On Jan 1, 2025, at 10:10?AM, Jim Shorney via groups.io <jimNU0C@...> wrote:
>
> ?
|
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
|
Okay Gary I will go do that right now.?
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
|
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
|
Re: VE3EFJ third mixer mod for the R4C
I've seen that board on Osh Park. I like the purple one. ? Jim, thanks for the reminder. Wow, Oshpark now wants USD $53.60 per 3-board order. It's much less expensive through JLCPCB at USD $3.50 for five boards and includes Global Standard Postal (i.e., slow) shipping. The attached .ZIP Gerber file of the R4 amp board can be uploaded to JLCPCB. HOWEVER, for anyone even remotely interested, I don't have a B.O.M. in a nicely formatted file. That will happen but not in the next several weeks. Paul, W9AC
|
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
toggle quoted message
Show quoted text
On Jan 1, 2025, at 11:58?AM, Jim Harris via groups.io <radiove1rb@...> wrote:
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
|
Re: VE3EFJ third mixer mod for the R4C
On 2025-01-01 08:33, Gary WB6OGD via groups.io wrote: It's a waste of time and money to design an AF amp for the Drake.
I used a (now) 75cent complete TDA2030 module from china.
*** I haven't had good luck with those. They market them as over 10W, but they're really only capable of 1W, running off 12V. And the onboard electrolytics are only 16V, so you are limited to that. The heatsink is not even adequate for 1W continuous. It can do maybe 1/4W continuous. I bought a baggie of 8 of them from Amazon, and so far, I've burned up 4 of them. I have had better luck with LM380 based amps. - Jerry, KF6VB
|
Mr. Rob... Can you please remind me what the low frequency attenuation was for your AMP-4? Thanks!
Joseph
On Wednesday, January 1, 2025 at 12:59:27 PM EST, Rob Sherwood via groups.io <rob@...> wrote:
My AMP-4 feedback loop was designed for about a 3 dB roll-off at 3 kHz.? Personal choice.? Rob, NC0B
> On Jan 1, 2025, at 10:10?AM, Jim Shorney via groups.io <jimNU0C@...> wrote:
>
> ?
|
Spot on... As I stated in my group posting, the original driver is old, and a less efficient speaker can be had when using more power. My MS-4 was treated to a hardwood ply escutcheon to mount the speaker, I used some open cell foam at the back to dampen it some, treated the enclosure with dynamat... I do whatever I need to to make this stuff how I want it to be. I don't have one shred of worry or thought in trying to keep it original at all. Its 2025, advances in technology allow us to do things Drake would not have been able to. When I did all this about 7-8 years ago, I tested the factory Jensen and the new driver side by side. Sweeping from 50 to 10K cycles... I confirmed beyond any doubt the old speaker was terrible.
On Wednesday, January 1, 2025 at 12:42:16 PM EST, kg9hfrank@... via groups.io <kg9hfrank@...> wrote:
All the talk about the audio amplifier on an R-4C intrigues me to ask the question, ¡°What are you doing about the speaker?¡± ? With a 50 year old speaker in some cases, what are you replacing it with, without doing any mechanical work?¡± ? ? ?Frank Krozel ? ? ? ? ? ?KG9H Life Member, ARRL ? ? (630) 924-1600 kg9hfrank@...
|
Frank,
I am running the audio out of my R4C into a CLEAR SPEECH noise filter, then....from the noise filter into a Kenwood SP-940 speaker with 3 filters in it.
Absolute Nirvana sound...Can pick up weak DX that doesn't move the meter.
?The Drake R4C out hears my Icom 7300, but quite a bit......
Bill N1WL
?William Losefsky? ?????????
On Wednesday, January 1, 2025 at 12:42:15 PM EST, kg9hfrank@... via groups.io <kg9hfrank@...> wrote:
All the talk about the audio amplifier on an R-4C intrigues me to ask the question, ¡°What are you doing about the speaker?¡± ? With a 50 year old speaker in some cases, what are you replacing it with, without doing any mechanical work?¡± ? ? ?Frank Krozel ? ? ? ? ? ?KG9H Life Member, ARRL ? ? (630) 924-1600 kg9hfrank@...
|
Jim I just hooked my older counter and it is reading 152 MHZ plus it minus. Now which one is right? Maybe this one where the voltage is so high. Maybe I should put a ground on RFC505 and see what happens?
Jim VE1RB
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 as the frequency is jumping around so is not locked. I wonder if that is a clue??
Jim VE1RB 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
|
Forget that idea as I turned the TR7 off and that frequency did not go away. Guess next it to try and measure voltages on both VCO¡¯s and see if that will show the bad part etc.?
Jim VE1RB
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 as the frequency is jumping around so is not locked. I wonder if that is a clue??
Jim VE1RB 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
|
Re: VE3EFJ third mixer mod for the R4C
My AMP-4 feedback loop was designed for about a 3 dB roll-off at 3 kHz. Personal choice. Rob, NC0B
toggle quoted message
Show quoted text
On Jan 1, 2025, at 10:10?AM, Jim Shorney via groups.io <jimNU0C@...> wrote:
?
Yeah, that works. The TDA chips are rock stable and practically bulletproof when implemented properly. I have one of the Velleman TDA2002 modules that I acquired some years back for my R4C, I just have not got a round tuit yet. One thing that I did do was to alter the capacitance in the feedback network to roll the audio off around 4KHz.
On Wed, 01 Jan 2025 08:33:53 -0800
"Gary WB6OGD via groups.io" <winbladgary@...> wrote:
It's a waste of time and money to design an AF amp for the Drake.
I used a (now) 75cent complete TDA2030 module from china.
Like this one:
--
73
-Jim
NU0C
|
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 as the frequency is jumping around so is not locked. I wonder if that is a clue??
Jim VE1RB
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
|
All the talk about the audio amplifier on an R-4C intrigues me to ask the question, ¡°What are you doing about the speaker?¡± ? With a 50 year old speaker in some cases, what are you replacing it with, without doing any mechanical work?¡± ??
? ? ?Frank Krozel ? ? ? ? ? ?KG9H Life Member, ARRL ? ? (630) 924-1600 kg9hfrank@...
|
Re: AF AMP VE3EFJ third mixer mod for the R4C
Gary!!! Bravo! I too used a device like that for mine( TDA7377)... I removed the original jensen speaker, used a lower efficiency driver, yet one with better listening specs. My MS-4 has been modified into a more practical speaker enclosure also. I tossed the cardboard speaker escutcheon and made a proper one out of hardwood ply. Lots of other things to make the box have more decent response also... Those TDA modules are great! I get about 10-11 watts from mine. 2.5 watts does not cut it when guys are now hell bent on 2.8kHz bandwidth or more. Doing all this and using one of Franks 2.8 filters was very liberating. I thought about using in bridged mode, yet 10-11 watts is flat enough.
On Wednesday, January 1, 2025 at 11:33:55 AM EST, Gary WB6OGD via groups.io <winbladgary@...> wrote:
It's a waste of time and money to design an AF amp for the Drake.
I used a (now) 75cent complete TDA2030 module from china.
?
Like this one:
https://www.ebay.com/itm/314750105717?_skw=TDa2030+amplifier+module&itmmeta=01JGHB55413WV2745A8XBJYQBN&hash=item4948917875:g:upwAAOSwiFZky38Y&itmprp=enc%3AAQAJAAAA8HoV3kP08IDx%2BKZ9MfhVJKl9LzhQlEV7hr7qISFGACsJ4nRv905MP85TlwPdXY5R6c3VMsAxJIQKAv5Wui8d0Yi5pi9YIYuzUCSjP5ml2suXZumYP9VjoXxEuLgFUi%2FbDTCLNL%2Bfzq1996uV4tf62yNmyWpQMXYoXUZz8Vv9amSvPAB9B%2B0dDCc1DrezcMlCO9tR6%2FQCZNyVOKUH0VaPBtchCvaYlnLrPBcthdKwTS0tsusftmUTkrWDt3q1FPcmtYKvA7qfjd%2FramvBIYhkHsdzm2t9cFMXaqQoBKG16X7Bgfc83okBCT8p2OAuM1pXVw%3D%3D%7Ctkp%3ABk9SR57SlKuEZQ
?
See my Folder in the Files section:
? ? "Drake R4A or R4B solid state AF Amp"
?
73,
Gary
WB6OGD
?
|
Re: VE3EFJ third mixer mod for the R4C
I've seen that board on Osh Park. I like the purple one. :D On Wed, 01 Jan 2025 09:02:55 -0800 "Paul Christensen via groups.io" <w9ac@...> wrote: The image below shows a discrete class AB amp layout meant specifically for the Drake R4 series -- 73 -Jim NU0C
|
Re: VE3EFJ third mixer mod for the R4C
Yeah, that works. The TDA chips are rock stable and practically bulletproof when implemented properly. I have one of the Velleman TDA2002 modules that I acquired some years back for my R4C, I just have not got a round tuit yet. One thing that I did do was to alter the capacitance in the feedback network to roll the audio off around 4KHz. On Wed, 01 Jan 2025 08:33:53 -0800 "Gary WB6OGD via groups.io" <winbladgary@...> wrote: It's a waste of time and money to design an AF amp for the Drake.
I used a (now) 75cent complete TDA2030 module from china.
Like this one:
-- 73 -Jim NU0C
|
Re: VE3EFJ third mixer mod for the R4C
On Wed, Jan 1, 2025 at 08:33 AM, Gary WB6OGD wrote:
It's a waste of time and money to design an AF amp for the Drake.
I used a (now) 75cent complete TDA2030 module from china.
?
The TDA series and LM380 are fine although I wanted lower noise with no detectable hiss at any setting of the AF control when using studio-grade headphones.?
?
The image below shows a discrete class AB amp layout meant specifically for the Drake R4 series.? It has on-board V regulation, PS decoupling, and two isolated analog ground planes that meet together at the at the V reg ground pin.? Loudspeaker current can't modulate the ground reference of the high-gain, low-noise front-end stage.?
?
The high-gain stage uses low-noise Toshiba transistors. The output cap is 4500 uF.? An additional regulated output can feed the PTO.? ? Sure, it's only communications-grade audio but anyone wishing to listen at my QTH, you're welcome to stop by and hear the difference.
?
Paul, W9AC
?
?
?
|
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
|
Rob Sherwood
Paul Christensen
Jim Shorney