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Need help with constant tone in audio output

 

I assume this tone is only present during receive.

Do you receive amateur signals when an antenna is attached? ?

How does the volume of this tone compare with the volume of received signals?

Can you describe the tone? ?Is it a steady dc note? ?What frequency?

Can you do things that cause the volume or frequency of this tone to change?

Does it change in volume when you turn down the volume control? ?(If not. problem is in the LM386)

Does it change in frequency as you tune the radio?

Does it change in frequency when you poke your finger around C102 in the BFO?

I suggest you work you way back through the receiver, shorting the signal to ground at each stage with a piece of wire to determine where the tone is coming from. ?Do you still have the tone when you short the top of C107 to ground? ?R37? ? Crystal side of C31? ?Crystal side of C23? ? Mixer side of C21? ?Mixer side of C13? ?Filter side of C11? ?The antenna? ??


I'm pretty sure it's ok to short those particular nodes to ground, but not my responsibility if you destroy something. ?You should look the schematics over hard, make sure you are probing the correct point, and verify that what you are doing won't cause harm.


> ?I was approved to join this group.

That's most reassuring.


Jerry Gaffke, KE7ER


On Sun, Feb 19, 2017 at 11:40 am, <chucke2@...> wrote:

Hi everyone. I was approved to join this group. I have a Bitx-40 XCVR. I have connected all the components to the board. I turn it on and can tune around. The Rx and Tx both work. But there is a tone coming out of the ¡®386. I cannot find the source of this tone. Has anyone come across this problem? I changed spkrs and have an 8 ohm in there now. Would appreciate any insite into this issue.

?
 

Also, it is possible that your tone is coming from the Raduino somehow. ?You might remove the Raduino and follow the WireUp instructions to use the analog VFO instead. ?See if that helps.
 

Thanks so much for responding Jerry. I answered your questions... Chuck

I assume this tone is only present during receive. Correct

Do you receive amateur signals when an antenna is attached? ?Yes

How does the volume of this tone compare with the volume of received signals? Very Very loud

Can you describe the tone? ?Is it a steady dc note? ?What frequency? Tone is a sine wave, estimate about 800-900 Hz.

Can you do things that cause the volume or frequency of this tone to change? Have disconnected all components {including display) . tone still there.

Does it change in volume when you turn down the volume control? ?(If not. problem is in the LM386) Yes

Does it change in frequency as you tune the radio? No

Does it change in frequency when you poke your finger around C102 in the BFO? will do

I suggest you work you way back through the receiver, shorting the signal to ground at each stage with a piece of wire to determine where the tone is coming from. ?Do you still have the tone when you short the top of C107 to ground? ?R37? ? Crystal side of C31? ?Crystal side of C23? ? Mixer side of C21? ?Mixer side of C13? ?Filter side of C11? ?The antenna? stay tuned for results.
 

Also, it is possible that your tone is coming from the Raduino somehow. ?You might remove the Raduino and follow the WireUp instructions to use the analog VFO instead. ?See if that helps. Have disconnected the Raduino, tone still there.
 

Did you enable the analog vfo by adding L4?

If the tone is still there with no vfo, that's a hint


On Sun, Feb 19, 2017 at 01:07 pm, <chucke2@...> wrote:

Have disconnected the Raduino, tone still there.

?
 

Good morning Jerry and the group,

Had to stop last night, having probed for nearly 10 hours. Jerry, my trouble shooting is hampered by not having an up-to-date schematic. My board is a Bitx40 V3. It's interesting to note that when I power the '40 up the tone is immediate and the rcvr comes on about a second later. I have all the components taken out of the '40 except the volume control... still the tone. I wonder if India could replace the board given the amount of time spent trying to get it working? I'll continue to trouble shoot today and will keep you and the group updated. BTW, the tone encountered is not a clicking noise.

73,
Chuck K3VPZ

From: "Jerry Gaffke via Groups.Io" <jgaffke@...>
To: [email protected]
Sent: Sunday, February 19, 2017 4:59:53 PM
Subject: Re: [BITX20] Need help with constant tone in audio output

Did you enable the analog vfo by adding L4?

If the tone is still there with no vfo, that's a hint


On Sun, Feb 19, 2017 at 01:07 pm, <chucke2@...> wrote:

Have disconnected the Raduino, tone still there.

?
 

Try a battery supply.? My shack supply does not play nice with the BitX.? A small wall wart 2A, 12V is silent.? I get tone with the shack PS.

Larry
KB3CUF

On Mon, Feb 20, 2017 at 8:01 AM, Chuck <chucke2@...> wrote:
Good morning Jerry and the group,

Had to stop last night, having probed for nearly 10 hours. Jerry, my trouble shooting is hampered by not having an up-to-date schematic. My board is a Bitx40 V3. It's interesting to note that when I power the '40 up the tone is immediate and the rcvr comes on about a second later. I have all the components taken out of the '40 except the volume control... still the tone. I wonder if India could replace the board given the amount of time spent trying to get it working? I'll continue to trouble shoot today and will keep you and the group updated. BTW, the tone encountered is not a clicking noise.

73,
Chuck K3VPZ

From: "Jerry Gaffke via Groups.Io" <jgaffke=[email protected]>
To: [email protected]
Sent: Sunday, February 19, 2017 4:59:53 PM
Subject: Re: [BITX20] Need help with constant tone in audio output

Did you enable the analog vfo by adding L4?

If the tone is still there with no vfo, that's a hint


On Sun, Feb 19, 2017 at 01:07 pm, <chucke2@...> wrote:

Have disconnected the Raduino, tone still there.

?
 

FIrst I am suspecting the power supply.

Second disconnect the volume plug and see, I would suspect the tone will be there if the PS is at fault.

Third If the tone stops then suspect the preamp transistor or earlier.

As you said you have disconnected the rest.

Raj



At 20/02/2017, you wrote:

Good morning Jerry and the group,

Had to stop last night, having probed for nearly 10 hours. Jerry, my trouble shooting is hampered by not having an up-to-date schematic. My board is a Bitx40 V3. It's interesting to note that when I power the '40 up the tone is immediate and the rcvr comes on about a second later. I have all the components taken out of the '40 except the volume control... still the tone. I wonder if India could replace the board given the amount of time spent trying to get it working? I'll continue to trouble shoot today and will keep you and the group updated. BTW, the tone encountered is not a clicking noise.

73,
Chuck K3VPZ

From: "Jerry Gaffke via Groups.Io" <jgaffke@...>
To: [email protected]
Sent: Sunday, February 19, 2017 4:59:53 PM
Subject: Re: [BITX20] Need help with constant tone in audio output

Did you enable the analog vfo by adding L4?

If the tone is still there with no vfo, that's a hint


On Sun, Feb 19, 2017 at 01:07 pm, <chucke2@...> wrote:
Have disconnected the Raduino, tone still there.

?
 

Good morning Larry,

Success! Using a battery cleared up the tone. Now on to packing it up in its enclosure. Many thanks to all for helping including Jerry!

73,
Chuck K3VPZ

From: "Larry Acklin" <acklin@...>
To: [email protected]
Sent: Monday, February 20, 2017 8:30:31 AM
Subject: Re: [BITX20] Need help with constant tone in audio output

Try a battery supply.? My shack supply does not play nice with the BitX.? A small wall wart 2A, 12V is silent.? I get tone with the shack PS.

Larry
KB3CUF

On Mon, Feb 20, 2017 at 8:01 AM, Chuck <chucke2@...> wrote:
Good morning Jerry and the group,

Had to stop last night, having probed for nearly 10 hours. Jerry, my trouble shooting is hampered by not having an up-to-date schematic. My board is a Bitx40 V3. It's interesting to note that when I power the '40 up the tone is immediate and the rcvr comes on about a second later. I have all the components taken out of the '40 except the volume control... still the tone. I wonder if India could replace the board given the amount of time spent trying to get it working? I'll continue to trouble shoot today and will keep you and the group updated. BTW, the tone encountered is not a clicking noise.

73,
Chuck K3VPZ

From: "Jerry Gaffke via Groups.Io" <jgaffke=[email protected]>
To: [email protected]
Sent: Sunday, February 19, 2017 4:59:53 PM
Subject: Re: [BITX20] Need help with constant tone in audio output

Did you enable the analog vfo by adding L4?

If the tone is still there with no vfo, that's a hint


On Sun, Feb 19, 2017 at 01:07 pm, <chucke2@...> wrote:

Have disconnected the Raduino, tone still there.

?
ken barnes
 

try large capasitor ie ?50uf ?25 volt working ? ? across power supply.............


On Monday, 20 February 2017, 13:51, Raj vu2zap <vu2zap@...> wrote:


FIrst I am suspecting the power supply.

Second disconnect the volume plug and see, I would suspect the tone will be there if the PS is at fault.

Third If the tone stops then suspect the preamp transistor or earlier.

As you said you have disconnected the rest.

Raj



At 20/02/2017, you wrote:

Good morning Jerry and the group,

Had to stop last night, having probed for nearly 10 hours. Jerry, my trouble shooting is hampered by not having an up-to-date schematic. My board is a Bitx40 V3. It's interesting to note that when I power the '40 up the tone is immediate and the rcvr comes on about a second later. I have all the components taken out of the '40 except the volume control... still the tone. I wonder if India could replace the board given the amount of time spent trying to get it working? I'll continue to trouble shoot today and will keep you and the group updated. BTW, the tone encountered is not a clicking noise.

73,
Chuck K3VPZ

From: "Jerry Gaffke via Groups.Io" <jgaffke@...>
To: [email protected]
Sent: Sunday, February 19, 2017 4:59:53 PM
Subject: Re: [BITX20] Need help with constant tone in audio output

Did you enable the analog vfo by adding L4?

If the tone is still there with no vfo, that's a hint


On Sun, Feb 19, 2017 at 01:07 pm, <chucke2@...> wrote:
Have disconnected the Raduino, tone still there.

?

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