Topics

LM324 AGC Issue

Murray Wills (ZL2IQ)
 

Hi I have built up one of the LM324 AGC kits from India and used all the usual sources for circuits and photos to make sure it is installed correctly. The instructions say that there should be 4 volts at PIN 3 on the LM324 but I only have .75 volts maximum.

Has anyone else had success with this kit?
if not is there a recommended kit
I have replaced the LM324 and the BC547 and found no difference.

Cheers
Murray ZL2IQ

 

Could not find the circuit, could you share so we can look at it and see what may be the issue!

Raj

At 19/10/2019, you wrote:
Hi I have built up one of the LM324 AGC kits from India and used all the usual sources for circuits and photos to make sure it is installed correctly. The instructions say that there should be 4 volts at PIN 3 on the LM324 but I only have .75 volts maximum.

Has anyone else had success with this kit?
if not is there a recommended kit
I have replaced the LM324 and the BC547 and found no difference.

Cheers
Murray ZL2IQ

MVS Sarma
 

Raj, 
It is there in files section og bitx20 groups site as pdf from vu3sua.
Regards 
Sarma vu3zmv

On Sat, 19 Oct 2019, 5:08 pm Raj vu2zap, <rajendrakumargg@...> wrote:
Could not find the circuit, could you share so we can look at it and see what may be the issue!

Raj

At 19/10/2019, you wrote:
>Hi I have built up one of the LM324 AGC kits from India and used all the usual sources for circuits and photos to make sure it is installed correctly. The instructions say that there should be 4 volts at PIN 3 on the LM324 but I only have .75 volts maximum.
>
>Has anyone else had success with this kit?
>if not is there a recommended kit
>I have replaced the LM324 and the BC547 and found no difference.
>
>Cheers
>Murray ZL2IQ




 

Check R2, probably a wrong value.

See if you have an PCB hair line short, hot the board up to a strong back light and see if you spot anything!

Raj

At 19/10/2019, you wrote:
Hi I have built up one of the LM324 AGC kits from India and used all the usual sources for circuits and photos to make sure it is installed correctly. The instructions say that there should be 4 volts at PIN 3 on the LM324 but I only have .75 volts maximum.

Has anyone else had success with this kit?
if not is there a recommended kit
I have replaced the LM324 and the BC547 and found no difference.

Cheers
Murray ZL2IQ

Murray Wills (ZL2IQ)
 

Thank you Raj I will try those today


From: BITX20@groups.io <BITX20@groups.io> on behalf of Raj vu2zap via Groups.Io <rajendrakumargg@...>
Sent: Sunday, October 20, 2019 1:42:51 AM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] LM324 AGC Issue
 
Check R2, probably a wrong value.

See if you have an PCB hair line short, hot the board up to a strong back light and see if you spot anything!

Raj

At 19/10/2019, you wrote:
>Hi I have built up one of the LM324 AGC kits from India and used all the usual sources for circuits and photos to make sure it is installed correctly. The instructions say that there should be 4 volts at PIN 3 on the LM324 but I only have .75 volts maximum.
>
>Has anyone else had success with this kit?
>if not is there a recommended kit
>I have replaced the LM324 and the BC547 and found no difference.
>
>Cheers
>Murray ZL2IQ




 

Hi Murry,

I built it and am currently using it without trouble. When setting it up, all voltages were able to attained without problem. Perhaps the LM324 is bad or you have it plugged in backwards.

Joel
N6ALT

Murray Wills (ZL2IQ)
 

Thanks Joel. I have replaced the LM324 just in case but still no luck.

Murray ZL2IQ


From: BITX20@groups.io <BITX20@groups.io> on behalf of Joel Caulkins/N6ALT via Groups.Io <caulktel@...>
Sent: Sunday, October 20, 2019 10:18:56 AM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] LM324 AGC Issue
 
Hi Murry,

I built it and am currently using it without trouble. When setting it up, all voltages were able to attained without problem. Perhaps the LM324 is bad or you have it plugged in backwards.

Joel
N6ALT

albert@...
 

Here is some information I passed to another person that helped them.
I had issues also but using the alternate calibration method, things popped right in.

Go to the amateurradiokits website.
You have to go to "My Account" dropdown (Orange Button)
Depending on the login state you may have to login.
There you will find a "downloads" link. (7th down)
Download the "uBitx Nextion Case" (last one, takes a while) 
Decompress is and look for a folder called "AGC" 
When you get to building / calibrating the AGC board use the "AGC Details.pdf" file found in the AGC folder! 
This is a multi-page PDF file.

Look at the entire file, at almost the end of the document is an alternate calibration method. Try that.

BTW:
DON'T download the second folder down (AGC) from the downloads amateurradiokits website. It will not give you ALL the information you need to know.
I used the AGC folder from the "ubitx nexton case" folder. (Spent a couple of days figuring that out.)


Hope this helps!
Albert
KE0PRX

Murray Wills (ZL2IQ)
 

Thank you. Murray ZL2IQ


From: BITX20@groups.io <BITX20@groups.io> on behalf of albert via Groups.Io <albert@...>
Sent: Monday, October 21, 2019 12:59:02 PM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] LM324 AGC Issue
 
Here is some information I passed to another person that helped them.
I had issues also but using the alternate calibration method, things popped right in.

Go to the amateurradiokits website.
You have to go to "My Account" dropdown (Orange Button)
Depending on the login state you may have to login.
There you will find a "downloads" link. (7th down)
Download the "uBitx Nextion Case" (last one, takes a while) 
Decompress is and look for a folder called "AGC" 
When you get to building / calibrating the AGC board use the "AGC Details.pdf" file found in the AGC folder! 
This is a multi-page PDF file.

Look at the entire file, at almost the end of the document is an alternate calibration method. Try that.

BTW:
DON'T download the second folder down (AGC) from the downloads amateurradiokits website. It will not give you ALL the information you need to know.
I used the AGC folder from the "ubitx nexton case" folder. (Spent a couple of days figuring that out.)


Hope this helps!
Albert
KE0PRX

Neil Tolman
 

Albert,
This download only works if you've purchased something from them. Is it possible you could share the pdf with us?
K1NBT
Neil

On Sunday, October 20, 2019, 7:59:09 PM EDT, <albert@...> wrote:


Here is some information I passed to another person that helped them.
I had issues also but using the alternate calibration method, things popped right in.

Go to the amateurradiokits website.
You have to go to "My Account" dropdown (Orange Button)
Depending on the login state you may have to login.
There you will find a "downloads" link. (7th down)
Download the "uBitx Nextion Case" (last one, takes a while) 
Decompress is and look for a folder called "AGC" 
When you get to building / calibrating the AGC board use the "AGC Details.pdf" file found in the AGC folder! 
This is a multi-page PDF file.

Look at the entire file, at almost the end of the document is an alternate calibration method. Try that.

BTW:
DON'T download the second folder down (AGC) from the downloads amateurradiokits website. It will not give you ALL the information you need to know.
I used the AGC folder from the "ubitx nexton case" folder. (Spent a couple of days figuring that out.)


Hope this helps!
Albert
KE0PRX

 

Here you go.

Joel
N6ALT

 

Sorry for the duplicate attachments, they are identical.

Joel

Joe Puma
 

You have to calibrate the POTs on the top row. It’s in the notes of the build and calibration. If you did that step then something is wrong. If I recall the second pot on the top of board from the left adjusts the voltage for the LM chip. The 4v is desired voltage to power LM chip.  

Joe
KD2NFC


On Oct 21, 2019, at 10:14 AM, Joel Caulkins/N6ALT <caulktel@...> wrote:

Here you go.

Joel
N6ALT
<AGC Details.pdf>
<AGC Details.pdf>

Neil Tolman
 

Thank You!
Neil
K1NBT

On Monday, October 21, 2019, 10:19:25 AM EDT, Joel Caulkins/N6ALT <caulktel@...> wrote:


Here you go.

Joel
N6ALT

ajparent1/KB1GMX
 

One further issue is to insure the wire from the base of
Q10 on the ubitx to the AGC board is very short!  It
has RF on it and a long wire will impact stability
and possibly introduce noises.

Better way to attach to base of Q10 is through a small resistor
of 100 ohms to reduce the amount of RF on the wire.

Allison

Murray Wills (ZL2IQ)
 

Thanks. Yes I have been following the instructions. I am going to check the resister values today as R1 or R2 could be wrong. M


From: BITX20@groups.io <BITX20@groups.io> on behalf of Joe Puma via Groups.Io <kd2nfc@...>
Sent: Tuesday, October 22, 2019 3:30:18 AM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] LM324 AGC Issue
 
You have to calibrate the POTs on the top row. It’s in the notes of the build and calibration. If you did that step then something is wrong. If I recall the second pot on the top of board from the left adjusts the voltage for the LM chip. The 4v is desired voltage to power LM chip.  

Joe
KD2NFC


On Oct 21, 2019, at 10:14 AM, Joel Caulkins/N6ALT <caulktel@...> wrote:

Here you go.

Joel
N6ALT
<AGC Details.pdf>
<AGC Details.pdf>

Murray Wills (ZL2IQ)
 

Allison. Thank you. That is a good tip.
I will introduce that resister once I have it working.
73 de
Murray ZL2IQ


From: BITX20@groups.io <BITX20@groups.io> on behalf of ajparent1/KB1GMX via Groups.Io <kb1gmx@...>
Sent: Tuesday, October 22, 2019 5:26:57 AM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] LM324 AGC Issue
 
One further issue is to insure the wire from the base of
Q10 on the ubitx to the AGC board is very short!  It
has RF on it and a long wire will impact stability
and possibly introduce noises.

Better way to attach to base of Q10 is through a small resistor
of 100 ohms to reduce the amount of RF on the wire.

Allison