Newfield Defender
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Wired in an external speaker to the cb yesterday and for some reason its not working well it is but so quiet you cant hear it. uping the volume does not help any ideas?
CB external speaker
- Thread starter Newfield Defender
- Start date
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wrong impedance?
Newfield Defender
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whats that then ?
Newfield Defender
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also just try it with out the external speaker pluged in and it does the same with out it
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In that case it sounds like the audio output transistor has blown 
.
.Newfield Defender
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so new cb or is it fixable
nathan5346
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i got a midland 38 with a magmount im selling £40
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Anything is fixable.....
Q is - do you have the knowledge or the money?
mite be cheaper to get another and then see if it can be fixed.
Newfield Defender
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only thing that worrys me is if i buy a new cb and it does it again could the external speaker be causing it
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Thought you'd sold that... ... ...
Fixable but you need some one in your area who can as if you have to post it to a repair shop then the P&P each way and the cost of the repair makes it cheaper to buy another cb.You could buy another and then put yours on evilbay with the fault noted ok you wont get a lot for it but its better than nothing.
nathan5346
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Never got back to me, its gathering dust atm
Clanforbes
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What rig is it?
Do you mean an external PA (public address) speaker?
Or an external loudspeaker?
In the case of an external loudspeaker, make sure you have it plugged into the correct socket on the back. This socket may be dirty and not giving a good connection, also, this could be why you no longer hear the internal speaker.
If you are getting sound out of the internal speaker then it will not be the audio amplifier IC. If the audio amp dies you don't usually hear anything at all.
Next. The microphone might have a broken wire, again, if you hear the internal speaker then this isn't the fault either.
The standard mic has 4 wires, some have 5. The way the mic works, there are three wires and ground. The easy way to knowhow many wires is to take the mic plug out and look at it, four holes, or 5 holes, or in old rigs, f pins (the old 5 pin plugs just push in, the others screw in.
One wire (usually red) is for the TX circuit (transmit.)
One wire (usually blue or black is for the RX circuit (receive.)
The other wires (usually white or yellow is the mic circuit (audio.)
The screen (bare wire usually) is the ground connection which is common to all circuits.
If it has a fifth wire then this will probably be a +5ve feed.
If the red wire is off or broken, either at the plug or hand unit, then the audio is barely audible. There is also a possibility that the tx/rx switch is dirty and stopping the connection.
If you have the PA speaker plugged in, and you key the mic, can you hear yourself (or feedback screeching?)
As an easy quick test, if it is a four wire mic, simple take the mic plug out and use a small metal screwdriver to joint the pins in the socket together in pairs. This will switch the audio circuit on when you find the correct pair.
It will do no harm to the rig if you connect up wrong pairs ONE AT A TIME.
The most common pair for the audio output and the gnd are diagonally opposite each other. But this is by no means the only possible match, try all of them in pairs - this gives you 6 choices in a 4 pin socket, top two left to right, bottom two left to right, left two up and down, right two up and down, then the two diagonals. One pair will set the rig to TX, one pair will set the rig to RX (the one you want) the rest will no doanything
BEWARE THOUGH IF IT IS A FIVE PIN SCREW-IN SOCKET. THIS WOULD MEAN THERE IS PROBABLY A +5V SUPPLY WHICH CAN, AND MOST PROBABLY WILL, KILL THE VOLTAGE REGULATOR IC IN THE RIG IF YOU SHORT IT TO GND.
Let me know the rig model and I'll see if I have diagrams for it. The three most common audio amplifier IC's are LA4455 (Amstrad an York cb's) LA7205 (most cybernet based cb's) and the LA7235. There is also a common one used in Uniden based sets which I cannot remember off the top of my head, but they tend to be indestructible anyway.
An excellent supplier for parts (and repairs) is Knightcb at Kirton in Lindsey. Knights Electrocom - The UK's No.1 for CB
I have no affiliation with Knights in any shape or form.
Ron.
Do you mean an external PA (public address) speaker?
Or an external loudspeaker?
In the case of an external loudspeaker, make sure you have it plugged into the correct socket on the back. This socket may be dirty and not giving a good connection, also, this could be why you no longer hear the internal speaker.
If you are getting sound out of the internal speaker then it will not be the audio amplifier IC. If the audio amp dies you don't usually hear anything at all.
Next. The microphone might have a broken wire, again, if you hear the internal speaker then this isn't the fault either.
The standard mic has 4 wires, some have 5. The way the mic works, there are three wires and ground. The easy way to knowhow many wires is to take the mic plug out and look at it, four holes, or 5 holes, or in old rigs, f pins (the old 5 pin plugs just push in, the others screw in.
One wire (usually red) is for the TX circuit (transmit.)
One wire (usually blue or black is for the RX circuit (receive.)
The other wires (usually white or yellow is the mic circuit (audio.)
The screen (bare wire usually) is the ground connection which is common to all circuits.
If it has a fifth wire then this will probably be a +5ve feed.
If the red wire is off or broken, either at the plug or hand unit, then the audio is barely audible. There is also a possibility that the tx/rx switch is dirty and stopping the connection.
If you have the PA speaker plugged in, and you key the mic, can you hear yourself (or feedback screeching?)
As an easy quick test, if it is a four wire mic, simple take the mic plug out and use a small metal screwdriver to joint the pins in the socket together in pairs. This will switch the audio circuit on when you find the correct pair.
It will do no harm to the rig if you connect up wrong pairs ONE AT A TIME.
The most common pair for the audio output and the gnd are diagonally opposite each other. But this is by no means the only possible match, try all of them in pairs - this gives you 6 choices in a 4 pin socket, top two left to right, bottom two left to right, left two up and down, right two up and down, then the two diagonals. One pair will set the rig to TX, one pair will set the rig to RX (the one you want) the rest will no doanything
BEWARE THOUGH IF IT IS A FIVE PIN SCREW-IN SOCKET. THIS WOULD MEAN THERE IS PROBABLY A +5V SUPPLY WHICH CAN, AND MOST PROBABLY WILL, KILL THE VOLTAGE REGULATOR IC IN THE RIG IF YOU SHORT IT TO GND.
Let me know the rig model and I'll see if I have diagrams for it. The three most common audio amplifier IC's are LA4455 (Amstrad an York cb's) LA7205 (most cybernet based cb's) and the LA7235. There is also a common one used in Uniden based sets which I cannot remember off the top of my head, but they tend to be indestructible anyway.
An excellent supplier for parts (and repairs) is Knightcb at Kirton in Lindsey. Knights Electrocom - The UK's No.1 for CB
I have no affiliation with Knights in any shape or form.
Ron.
Last edited:
Clanforbes
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Extremely unlikely that an external speaker would kill a rig unless it has a serious short, then you wouldn't hear anything at all. Plug a set of headphones in temporarily (probably will have to wiggle plug out a little for a connection if they are stereo phones) to test for sound.
Assuming you have a set of phones with 3mm jack plug, that is. Most personal head phones.
BUT KEEP THE VOLUME AT MINIMUM OR YOU'LL WRECK YOUR EARS and probably the earpieces.
