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Lost audio from receiver

 

After some other testing on a BitX40 that was working well, it is likely that 12v (or even 24v) touched one of the speaker leads. Now I have essentially no audio out from the radio. On very strong signals and at maximum volume I can hear a weak and very distorted sound out of either the speaker or a separate speaker/mic, but it is not copyable and only just recognizeable as a signal. Listening on another receiver and watching the output, transmit seems fine. It sounds clear and undistorted and the power out is pretty normal. I checked the voltages around Q16 and they are exactly as expected in receive and transmit. The suspicion to me is that the LM386 has "blown", but there are no obvious marks on the board on any components. Is there someplace else I should look before trying to replace that chip?

As to technique for repairing that IC, if it is the problem, I seem to recall a method that involved just cutting the legs off and soldering them to a new chip. Is that a viable way to go?

While I've never owned a barrel of monkees, it? is hard to imagine that could be more fun than the BitX, but I do seem to get myself in trouble playing with it.

=Vic=
 

I think you're right, probably blew the LM386.
And nothing else.

Clipping leads and just leaving them in place sounds fine, or could?
heat them up and pull them out one by one using soldering iron and needle nose pliers.
I would not bother trying to suck the solder out of all those holes, just snip the bottom half of the legs off the new part
and solder it to the surface of the board.

An alternative is to buy some LM386 amp kit, and wire it into the existing volume control pot:
? ??


On Sun, Feb 11, 2018 at 12:52 pm, Vic WA4THR wrote:
After some other testing on a BitX40 that was working well, it is likely that 12v (or even 24v) touched one of the speaker leads. Now I have essentially no audio out from the radio. On very strong signals and at maximum volume I can hear a weak and very distorted sound out of either the speaker or a separate speaker/mic, but it is not copyable and only just recognizeable as a signal. Listening on another receiver and watching the output, transmit seems fine. It sounds clear and undistorted and the power out is pretty normal. I checked the voltages around Q16 and they are exactly as expected in receive and transmit. The suspicion to me is that the LM386 has "blown", but there are no obvious marks on the board on any components. Is there someplace else I should look before trying to replace that chip?

As to technique for repairing that IC, if it is the problem, I seem to recall a method that involved just cutting the legs off and soldering them to a new chip. Is that a viable way to go?

While I've never owned a barrel of monkees, it? is hard to imagine that could be more fun than the BitX, but I do seem to get myself in trouble playing with it.

=Vic=
 

Or use a socket for the LM386
Or get a cheap AF amplifier from bangood etc





Regards
Lawrence

On Sun, Feb 11, 2018 at 10:46 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
I think you're right, probably blew the LM386.
And nothing else.

Clipping leads and just leaving them in place sounds fine, or could?
heat them up and pull them out one by one using soldering iron and needle nose pliers.
I would not bother trying to suck the solder out of all those holes, just snip the bottom half of the legs off the new part
and solder it to the surface of the board.

An alternative is to buy some LM386 amp kit, and wire it into the existing volume control pot:
? ??


On Sun, Feb 11, 2018 at 12:52 pm, Vic WA4THR wrote:
After some other testing on a BitX40 that was working well, it is likely that 12v (or even 24v) touched one of the speaker leads. Now I have essentially no audio out from the radio. On very strong signals and at maximum volume I can hear a weak and very distorted sound out of either the speaker or a separate speaker/mic, but it is not copyable and only just recognizeable as a signal. Listening on another receiver and watching the output, transmit seems fine. It sounds clear and undistorted and the power out is pretty normal. I checked the voltages around Q16 and they are exactly as expected in receive and transmit. The suspicion to me is that the LM386 has "blown", but there are no obvious marks on the board on any components. Is there someplace else I should look before trying to replace that chip?

As to technique for repairing that IC, if it is the problem, I seem to recall a method that involved just cutting the legs off and soldering them to a new chip. Is that a viable way to go?

While I've never owned a barrel of monkees, it? is hard to imagine that could be more fun than the BitX, but I do seem to get myself in trouble playing with it.

=Vic=
Dennis Yancey
 

Put a socket in. That way you only need to fix the board once.. lm386 chips are cheap.

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