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uniden 76xl cb/pa switch help
- Thread starter dirtyjob
- Start date
Ok, you got a color code...
You have to trace those wires back thru that loom, and notice where they go - what parts on the board they solder to - the wires will be to a hole, but a trace comes from that hole to a part - that's what we need to know.
Why?
CB / PA switch does two things.
Redirects speaker output to a SEPARATE jack (Your PA jack on the back)
as well as,
Tell the radios PLL - DO NOT transmit. In PA mode, you're not using it to do that, you're using the Audio amp to send audio to an external PA-type of speaker.
It's why you have 5 wires.
One pair for the PLL - breaks a connection.
The other 3 directs Audio Amp "audio output" to one of two terminals.
You won't hear anything until you take the Audio amp output, and connect the right wire to the other "right" wire to run the internal speaker so you can even hear RX.
The External SP jack is designed, so that when you don't have anything connected to it, it runs the INTERNAL speaker instead.
The EXT SP jack is not the PA jack. PA jack is also wired so you can hear the RX you'd would hear in the INTERNAL speaker using RX mode - just turns off TX mode. but lets' you hear RX thru that PA speaker.
You have to trace those wires back thru that loom, and notice where they go - what parts on the board they solder to - the wires will be to a hole, but a trace comes from that hole to a part - that's what we need to know.
Why?
CB / PA switch does two things.
Redirects speaker output to a SEPARATE jack (Your PA jack on the back)
as well as,
Tell the radios PLL - DO NOT transmit. In PA mode, you're not using it to do that, you're using the Audio amp to send audio to an external PA-type of speaker.
It's why you have 5 wires.
One pair for the PLL - breaks a connection.
The other 3 directs Audio Amp "audio output" to one of two terminals.
You won't hear anything until you take the Audio amp output, and connect the right wire to the other "right" wire to run the internal speaker so you can even hear RX.
The External SP jack is designed, so that when you don't have anything connected to it, it runs the INTERNAL speaker instead.
The EXT SP jack is not the PA jack. PA jack is also wired so you can hear the RX you'd would hear in the INTERNAL speaker using RX mode - just turns off TX mode. but lets' you hear RX thru that PA speaker.
Hmm...
A PC76 is the simpler brother to the PC-78 - meaning more point to point wiring - This also means things like speaker wire is not an infinite length and the colors of the wires are not cast in stone.
So that means the switches were harnessed - but were hand soldered to the front panel in earlier versions of the 76 - using what was on spools or even on the floor.
They then went to headers to improve efficiency - so the wiring went to loom then branched off - integrated into the loom, to a single spot containing the header for that switch. Which then the foil side of these headers routed to the various spots.
So Black and Orange - got you RX, I think you are telling me you got the INTERNAL speaker to work - if that is the case, then the EXT SP wiring has been found - for it uses a tab on the jack that when empty, shorts to INTERNAL Speaker - when you plug in an external speaker - that "tab" opens up (like a switch) disconnects the INTERAL speaker and then all the audio goes to the External speaker.
Go to the Foil side and trace the "Black" from the harness to what component - same for "Orange" - Why? You have to find which wire powers the speakers - either get power thru one of these two wires - Sending (the origin of) power thru the switch to power one of either the internal and EXT speaker or the PA speaker. One of these two wires goes to the Back, towards those jacks - while another heads to a Transformer.
So those "two" have a third, which goes also to the back, thru that harness - that wire should only short - thru a CONTINUITY CHECK - to the PA Speaker jack.
This may mean one goes to the :"Mod transformer" (in that area) The other two would go to the rear jacks for PA and EXT. Speaker. The one to the "Mod Transformer" is common of the two. Of these three The other two wires are NOT common to each other so they short only to common - never to the other.
White and Pink (Or a similar pair from the CB/PA Switch) head to the opposite side of the board, by the Pre-Driver "short out" together in CB mode - but not in PA mode - at the same time that common wire on the other pole then shorts out to EXT speaker ONLY - does not short across - so once the EXT and PA speaker stuff works right, you're done with that side.
For TX, you just have to find the correct orientation of the opposite pole switch contacts to short across when the CB/PA switch is in CB.
Locate R44, find it's trace on the bottom, it should go to a spot that will eventually lift off the board with a wire that is similar in color code to the Pink/White pair - that one is your TX wire.
Just remember to keep the POLES of the switch separate - one pole is for speaker routing, the other is just to turn on or off the TX side.
A PC76 is the simpler brother to the PC-78 - meaning more point to point wiring - This also means things like speaker wire is not an infinite length and the colors of the wires are not cast in stone.
So that means the switches were harnessed - but were hand soldered to the front panel in earlier versions of the 76 - using what was on spools or even on the floor.
They then went to headers to improve efficiency - so the wiring went to loom then branched off - integrated into the loom, to a single spot containing the header for that switch. Which then the foil side of these headers routed to the various spots.
So Black and Orange - got you RX, I think you are telling me you got the INTERNAL speaker to work - if that is the case, then the EXT SP wiring has been found - for it uses a tab on the jack that when empty, shorts to INTERNAL Speaker - when you plug in an external speaker - that "tab" opens up (like a switch) disconnects the INTERAL speaker and then all the audio goes to the External speaker.
Go to the Foil side and trace the "Black" from the harness to what component - same for "Orange" - Why? You have to find which wire powers the speakers - either get power thru one of these two wires - Sending (the origin of) power thru the switch to power one of either the internal and EXT speaker or the PA speaker. One of these two wires goes to the Back, towards those jacks - while another heads to a Transformer.
So those "two" have a third, which goes also to the back, thru that harness - that wire should only short - thru a CONTINUITY CHECK - to the PA Speaker jack.
This may mean one goes to the :"Mod transformer" (in that area) The other two would go to the rear jacks for PA and EXT. Speaker. The one to the "Mod Transformer" is common of the two. Of these three The other two wires are NOT common to each other so they short only to common - never to the other.
White and Pink (Or a similar pair from the CB/PA Switch) head to the opposite side of the board, by the Pre-Driver "short out" together in CB mode - but not in PA mode - at the same time that common wire on the other pole then shorts out to EXT speaker ONLY - does not short across - so once the EXT and PA speaker stuff works right, you're done with that side.
For TX, you just have to find the correct orientation of the opposite pole switch contacts to short across when the CB/PA switch is in CB.
Locate R44, find it's trace on the bottom, it should go to a spot that will eventually lift off the board with a wire that is similar in color code to the Pink/White pair - that one is your TX wire.
Just remember to keep the POLES of the switch separate - one pole is for speaker routing, the other is just to turn on or off the TX side.
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