Need wiring to CB-PA switch.

[Mark A Bradley]

Good day ,hello guys, just a quicky, (That's what she said ), I have another Cobra 25 NW LTD Classic,board number (see pic). I noticed it had been mess with,and has different color pull ties holding the harness. I sent a few pics of the switch,now you can see,sticky fingers had been in this radio. Thats it for now, hope your all doing well,and of course, I appreciate the help from anyone who may have all the papers on this wiring to the switch. What it is,I have no volume,no PA,and I can hear the speaker click when I turn on the radio,had a light white noise for a time,but no more,after I did a Receive tune,don't know,but I am peaked out,also cannot get my 3.20v, it stays at 8.??V. I noticed a Varactor installed in D2,I put in a fresh Varactor,I have my frequency,but no RX.Varactor number NTE611,same that was there. Any other questions,feel free to ask, I think I have it covered. Thanks,glad it isn't a SMD board,what a pain,to small of a part,and my big hands and soldering iron. Anyone know of a SMD soldering iron that works,without burning down the house,( Board ). Take care,have a great Thursday,almost Friday.Later. And I have red and green light,like watching Sesame Street, Stop,Go,Stop,Go. Oh,only to be young again.Duh,Later,again.
.

 

[Eldorado828]

Man!! That tack solder job shows whoever was in there didn't need to be in there....

Look at that!

 

[Handy Andy]

The CB/PA switch is a simple DPDT - you just have to find "common" on the side that routes Audio Out from the Speaker terminals - to EXT Speaker and PA Speaker...

So to simplify - lets look at this
from an outline view

Each side of the switch has pins
each side or ROW of Pins are their own circuit
they are ISOLATED from each other but are
physically connected to the same LEVER to
make them work together in unison.
​

The Other two wires on the other side of that same switch - are to "turn on" the TX side.

• In PA - it interrupts the TX power to the PREDRIVER when you key the radio.
  • No RF is Generated
• In CB - Black wire routes to where you "ground" MIC Jack Pin 3
  • - this completes a circuit in CB Mode
  • - thru this switch power is allowed, the Predriver turns on, to get what comes out of IC 3 and build up RF-power to turn on the Driver and Final

See those Black and Pink? You have a shot of that in one of your photos,

• - that Pink wire is the one that heads off to the Predrivers "Return" lead
• - the Black wire heads off to the "main Terminal Bock" a bunch of solder pads

The Black wire then completes the circuit to MIC Pin 3 - which is soldered to this Terminal "block"

• - that allow the wires to the Mic and Front panel switches to land here and the "block" has all the holes going to a common "hole" for either a front panel switch - or the Mic Jack
• - in this case, that Black wire - jumpers over to the set of holes that go to MIC Pin 3 jack
  • - for the purpose of when grounded - the Pink allow power to flow, from the Predriver - thru the CB side of the CB PA switch - to Mic Pin 3 - and then through the Handset.
  • The Hansdet - GROUNDS this pin thru it's keyswitch back to SHIELD/Ground wire that heads off to MIC JACK Pin 1 GROUND when your in CB mode to TX.

I'm trying to keep this simple...

• This simple wiring sounds complex but when you notice the speaker doesn't work UNLESS the mic cord is installed, this is why - the Speaker either internal or External or PA - needs to complete it's circuit thru the Mic Pin 1 Ground From Mic Pin 4.
• Pin 3 - GROUNDs to Pin 1 thru the handset to allow the power flowing thru the Pink wire thru black into and back out of the handset - to even produce RF (added) when in CB mode.
• When you're in PA mode, the Black and Pink are disconnected from each other and the Predriver doesn't turn on. The wires on the other half of the switch then send Speaker Out from the Audio Amp - to the proper EXT or PA speaker jack. (This is thru the contacts in the switch - you're now shorting the BLUE wire to GREEN in PA mode.

Those Blue and Amber wires on one side of the switch are for that CB mode and EXT Speaker. They head off to the back panel...Blue fetches the Audio amps output and routes it to the Switch's "Common" on the one pole used for speaker routing - AMBER then connects Audio to the EXT Speaker "connection" tab - it's why you see this schematic symbol...

When you hook up the mini-plug into the jack,
the Normally Closed switch is opened
- disconnecting the internal speaker
- you hear audio now thru the external speaker
- the Ring is grounded to foil ground
- same ground as battery ground and where Speaker Negative Return goes​

Because you took photos earlier - we have archived a good example...

Here...

See the BLUE AMBER and GREEN wires?
There's your answer...​

It takes 3 wires for the Speaker out routing,

• BLUE - one wire GOES IN to the switch (From the transformer)
• AMBER- one wire head off to the EXT SP tab, that when empty (no plug in the jack) that shorts to a wire that leads to the INTERNAL Speaker "+" wire. - the Negative "-" wire from the Speaker routes back to that other hole right next to the Positive speaker wire - to another wire - that heads back to the Mic Jack - Pin 4.
• GREEN - look carefully in the photo - the Green wire heads to the other Jack header - which is your PA.
• Because of the soldering condition of the other wires, this one is pretty straightforward repair - the Green wire is the PA Output side of the CB/PA Switch.

When you're "listening" or in RX mode, Pin 4 is speaker "return" - which shorts to Pin 1 - and heads off to ground.

So place your Green wire onto the row of pins that have the Blue and Amber - Solder the green to that top terminal for that ROW. You should have speaker and PA works too.

Pink and Black - again head to the Predriver - and the solder lands for MIC Jack Pin 3.

You can see where several "black" wires solder to a specific land area on the board.
Look carefully, there are some resistors and capacitors in this area
you'll see this area is also ISOLATED from Board ground and Case or Chassis grounds
- which has it's own "tie off" to the specific spot
- reduces noise and makes rewiring the mic easier.
MIC audio routes to here, filters, then heads off to Dynamike​

Your Pink wire - heads back by the Predriver - shown here...

​

So your Pink wire goes to a Resistor and Filter cap - both need to be there - it's how RF power can even get produced.by the Predriver.

So now you know how the radio's CB and PA switch works.

If you can't get any RF - then the PREDRIVER may have ben damaged and needs to be replaced,

 

[Mark A Bradley]

The CB/PA switch is a simple DPDT - you just have to find "common" on the side that routes Audio Out from the Speaker terminals - to EXT Speaker and PA Speaker...

View attachment 47331
So to simplify - lets look at this
from an outline view
View attachment 47388
Each side of the switch has pins
each side or ROW of Pins are their own circuit
they are ISOLATED from each other but are
physically connected to the same LEVER to
make them work together in unison.
​

The Other two wires on the other side of that same switch - are to "turn on" the TX side.

• In PA - it interrupts the TX power to the PREDRIVER when you key the radio.
  • No RF is Generated
• In CB - Black wire routes to where you "ground" MIC Jack Pin 3
  • - this completes a circuit in CB Mode
  • - thru this switch power is allowed, the Predriver turns on, to get what comes out of IC 3 and build up RF-power to turn on the Driver and Final

See those Black and Pink? You have a shot of that in one of your photos,

• - that Pink wire is the one that heads off to the Predrivers "Return" lead
• - the Black wire heads off to the "main Terminal Bock" a bunch of solder pads

The Black wire then completes the circuit to MIC Pin 3 - which is soldered to this Terminal "block"

• - that allow the wires to the Mic and Front panel switches to land here and the "block" has all the holes going to a common "hole" for either a front panel switch - or the Mic Jack
• - in this case, that Black wire - jumpers over to the set of holes that go to MIC Pin 3 jack
  • - for the purpose of when grounded - the Pink allow power to flow, from the Predriver - thru the CB side of the CB PA switch - to Mic Pin 3 - and then through the Handset.
  • The Hansdet - GROUNDS this pin thru it's keyswitch back to SHIELD/Ground wire that heads off to MIC JACK Pin 1 GROUND when your in CB mode to TX.

I'm trying to keep this simple...

• This simple wiring sounds complex but when you notice the speaker doesn't work UNLESS the mic cord is installed, this is why - the Speaker either internal or External or PA - needs to complete it's circuit thru the Mic Pin 1 Ground From Mic Pin 4.
• Pin 3 - GROUNDs to Pin 1 thru the handset to allow the power flowing thru the Pink wire thru black into and back out of the handset - to even produce RF (added) when in CB mode.
• When you're in PA mode, the Black and Pink are disconnected from each other and the Predriver doesn't turn on. The wires on the other half of the switch then send Speaker Out from the Audio Amp - to the proper EXT or PA speaker jack. (This is thru the contacts in the switch - you're now shorting the BLUE wire to GREEN in PA mode.

Those Blue and Amber wires on one side of the switch are for that CB mode and EXT Speaker. They head off to the back panel...Blue fetches the Audio amps output and routes it to the Switch's "Common" on the one pole used for speaker routing - AMBER then connects Audio to the EXT Speaker "connection" tab - it's why you see this schematic symbol...

View attachment 47386
When you hook up the mini-plug into the jack,
the Normally Closed switch is opened
- disconnecting the internal speaker
- you hear audio now thru the external speaker
- the Ring is grounded to foil ground
- same ground as battery ground and where Speaker Negative Return goes​

Because you took photos earlier - we have archived a good example...

Here...

View attachment 47328
See the BLUE AMBER and GREEN wires?
There's your answer...​

It takes 3 wires for the Speaker out routing,

• BLUE - one wire GOES IN to the switch (From the transformer)
• AMBER- one wire head off to the EXT SP tab, that when empty (no plug in the jack) that shorts to a wire that leads to the INTERNAL Speaker "+" wire. - the Negative "-" wire from the Speaker routes back to that other hole right next to the Positive speaker wire - to another wire - that heads back to the Mic Jack - Pin 4.
• GREEN - look carefully in the photo - the Green wire heads to the other Jack header - which is your PA.
• Because of the soldering condition of the other wires, this one is pretty straightforward repair - the Green wire is the PA Output side of the CB/PA Switch.

When you're "listening" or in RX mode, Pin 4 is speaker "return" - which shorts to Pin 1 - and heads off to ground.

So place your Green wire onto the row of pins that have the Blue and Amber - Solder the green to that top terminal for that ROW. You should have speaker and PA works too.

Pink and Black - again head to the Predriver - and the solder lands for MIC Jack Pin 3.

View attachment 47329
You can see where several "black" wires solder to a specific land area on the board.
Look carefully, there are some resistors and capacitors in this area
you'll see this area is also ISOLATED from Board ground and Case or Chassis grounds
- which has it's own "tie off" to the specific spot
- reduces noise and makes rewiring the mic easier.
MIC audio routes to here, filters, then heads off to Dynamike​

Your Pink wire - heads back by the Predriver - shown here...

View attachment 47330​

So your Pink wire goes to a Resistor and Filter cap - both need to be there - it's how RF power can even get produced.by the Predriver.

So now you know how the radio's CB and PA switch works.

If you can't get any RF - then the PREDRIVER may have ben damaged and needs to be replaced,

Thanks,very interesting,glad the pictures ce in handy I just got your post,it's 3:30 in the morning. I will look into later this morning,this radio looks like the wiring was redone,as the pull ties look different? I did repair that wire,I look at a few other 25's I have in my cabinet,that helped move that wire,just copied off the other radio That was a nasty solder job,looked like the wire was not even attached. Will post later today,going over the wiring,and about the driver,that blew out on me,just after I moved that wire. Now I was able to see the majic smoke,what a stinking smoke bomb. That's sucker smoked up the garage,ok post later, Thank you again every one.

 

[Mark A Bradley]

Use by

The CB/PA switch is a simple DPDT - you just have to find "common" on the side that routes Audio Out from the Speaker terminals - to EXT Speaker and PA Speaker...

View attachment 47331
So to simplify - lets look at this
from an outline view
View attachment 47388
Each side of the switch has pins
each side or ROW of Pins are their own circuit
they are ISOLATED from each other but are
physically connected to the same LEVER to
make them work together in unison.
​

The Other two wires on the other side of that same switch - are to "turn on" the TX side.

• In PA - it interrupts the TX power to the PREDRIVER when you key the radio.
  • No RF is Generated
• In CB - Black wire routes to where you "ground" MIC Jack Pin 3
  • - this completes a circuit in CB Mode
  • - thru this switch power is allowed, the Predriver turns on, to get what comes out of IC 3 and build up RF-power to turn on the Driver and Final

See those Black and Pink? You have a shot of that in one of your photos,

• - that Pink wire is the one that heads off to the Predrivers "Return" lead
• - the Black wire heads off to the "main Terminal Bock" a bunch of solder pads

The Black wire then completes the circuit to MIC Pin 3 - which is soldered to this Terminal "block"

• - that allow the wires to the Mic and Front panel switches to land here and the "block" has all the holes going to a common "hole" for either a front panel switch - or the Mic Jack
• - in this case, that Black wire - jumpers over to the set of holes that go to MIC Pin 3 jack
  • - for the purpose of when grounded - the Pink allow power to flow, from the Predriver - thru the CB side of the CB PA switch - to Mic Pin 3 - and then through the Handset.
  • The Hansdet - GROUNDS this pin thru it's keyswitch back to SHIELD/Ground wire that heads off to MIC JACK Pin 1 GROUND when your in CB mode to TX.

I'm trying to keep this simple...

• This simple wiring sounds complex but when you notice the speaker doesn't work UNLESS the mic cord is installed, this is why - the Speaker either internal or External or PA - needs to complete it's circuit thru the Mic Pin 1 Ground From Mic Pin 4.
• Pin 3 - GROUNDs to Pin 1 thru the handset to allow the power flowing thru the Pink wire thru black into and back out of the handset - to even produce RF (added) when in CB mode.
• When you're in PA mode, the Black and Pink are disconnected from each other and the Predriver doesn't turn on. The wires on the other half of the switch then send Speaker Out from the Audio Amp - to the proper EXT or PA speaker jack. (This is thru the contacts in the switch - you're now shorting the BLUE wire to GREEN in PA mode.

Those Blue and Amber wires on one side of the switch are for that CB mode and EXT Speaker. They head off to the back panel...Blue fetches the Audio amps output and routes it to the Switch's "Common" on the one pole used for speaker routing - AMBER then connects Audio to the EXT Speaker "connection" tab - it's why you see this schematic symbol...

View attachment 47386
When you hook up the mini-plug into the jack,
the Normally Closed switch is opened
- disconnecting the internal speaker
- you hear audio now thru the external speaker
- the Ring is grounded to foil ground
- same ground as battery ground and where Speaker Negative Return goes​

Because you took photos earlier - we have archived a good example...

Here...

View attachment 47328
See the BLUE AMBER and GREEN wires?
There's your answer...​

It takes 3 wires for the Speaker out routing,

• BLUE - one wire GOES IN to the switch (From the transformer)
• AMBER- one wire head off to the EXT SP tab, that when empty (no plug in the jack) that shorts to a wire that leads to the INTERNAL Speaker "+" wire. - the Negative "-" wire from the Speaker routes back to that other hole right next to the Positive speaker wire - to another wire - that heads back to the Mic Jack - Pin 4.
• GREEN - look carefully in the photo - the Green wire heads to the other Jack header - which is your PA.
• Because of the soldering condition of the other wires, this one is pretty straightforward repair - the Green wire is the PA Output side of the CB/PA Switch.

When you're "listening" or in RX mode, Pin 4 is speaker "return" - which shorts to Pin 1 - and heads off to ground.

So place your Green wire onto the row of pins that have the Blue and Amber - Solder the green to that top terminal for that ROW. You should have speaker and PA works too.

Pink and Black - again head to the Predriver - and the solder lands for MIC Jack Pin 3.

View attachment 47329
You can see where several "black" wires solder to a specific land area on the board.
Look carefully, there are some resistors and capacitors in this area
you'll see this area is also ISOLATED from Board ground and Case or Chassis grounds
- which has it's own "tie off" to the specific spot
- reduces noise and makes rewiring the mic easier.
MIC audio routes to here, filters, then heads off to Dynamike​

Your Pink wire - heads back by the Predriver - shown here...

View attachment 47330​

So your Pink wire goes to a Resistor and Filter cap - both need to be there - it's how RF power can even get produced.by the Predriver.

So now you know how the radio's CB and PA switch works.

If you can't get any RF - then the PREDRIVER may have ben damaged and needs to be replaced,

Hey,how you doing,I am going to photograph the inside of this radio. This is a front Mike mount,and the reason of the picture is,I don't see a black wire on the CB/ PA switch,and I don't t see most of the wires you are showing. I will take a picture of the board number,and see what is going on. Thanks,Mark??????

 

[Handy Andy]

I sorry, if you cannot figure out the process having a radio to show you with it's own color coding and how the switch gets wired, then I cannot provide any more direction than for you to re-read the instructions in the premise of the troubleshooting...

Maybe this would help...
Locate the CB/PA switch...
Find the wires and their color code...
Locate their position on Your board..
Refer to the photos supplied...
You should be thinking "This color wire is here but mine it's this color" - so develop a reference chart for the colors shown in the photo to the new ones you have in your radio.

 

[Mark A Bradley]

I sorry, if you cannot figure out the process having a radio to show you with it's own color coding and how the switch gets wired, then I cannot provide any more direction than for you to re-read the instructions in the premise of the troubleshooting...

Maybe this would help...
Locate the CB/PA switch...
Find the wires and their color code...
Locate their position on Your board..
Refer to the photos supplied...
You should be thinking "This color wire is here but mine it's this color" - so develop a reference chart for the colors shown in the photo to the new ones you have in your radio.

Hey,that's fine,I have the manual,I will look at the board numbers,or I would pull another radio and give it my all. You and Eldorado 848 did great. All is appreciated,enjoy your Sunday.If and when I finish,I may post wires and the numbers they go to,I see Eldorado posted a picture,I shall see if it matches. Thanks to all.

 

[Handy Andy]

So you know:

Cobra 25/PC-66/PC68 series radios did PA switches differently than their larger Cousins the Cobra 29 and Uniden 76/78 series...

Cobra 25 / Uniden PC-66/68 Series:
The CB PA switch connected the Pre-driver DIRECTLY to the Mic Pin 3.- and grounded the Pre-drivers Emitter Leg to transmit. Completes a circuit.

Cobra 29 / Uniden PC-76/78 Series:
The CB/PA switch applied POWER to TR-21 - when turned on, would send power to TX side and included the Pre-Driver - Mic Pin 3 simply turned on and off TR21 - whether it had power to the Collector thru the CB side of the CB/PA switch - or not.

Your Color code for the radio you sent pictures of
​

 

[Handy Andy]

It is unfortunate but I have to issue this warning again:

Please keep the radios to topic.
Above is a perfect example of the confusion it can cause for both the posters and those attempting to answer.
Two ways of wiring a simple switch in two different radios had to be shown to CLARIFY the posters questions.
Again, please start a new thread and keep the radios separate...else too much time and confusion can result due to the required information needed to answer the question.
​

 

[Mark A Bradley]

It is unfortunate but I have to issue this warning again:

Please keep the radios to topic.
Above is a perfect example of the confusion it can cause for both the posters and those attempting to answer.
Two ways of wiring a simple switch in two different radios had to be shown to CLARIFY the posters questions.
Again, please start a new thread and keep the radios separate...else too much time and confusion can result due to the required information needed to answer the question.
​

Sorry,did not know I was off topic, I needed the wiring for the switch,thats it. If you have issues with what I need, then I won't ask for help. Just remove me from the Forum, you have been very helpfull, but if you are having issues with me, just remove me, I dont need help, it seems you have it in for me. I posted those pics to help you out, to make it easier for you, I thought a picture of the board may help you out with the switch, possibly a different board, as the wiring pictures pictures that were posted for me to see was different, that's how it got off topic, just asking for a simple where the wire go, as for where they go on the board, I can probably use another radio to find where they go, just needed the switch wiring. You saw the solder job, I was not sure if this was correct, as I have o other books or information on if this was a correct solder job or not. Seems that the radio wiring on some of the same radios are different, mostly the same, but where do you got get the correct switch wiring, cant find it on the internet, only seems that the Techs have all the information that a person may need, otherwise flying blind. Sorry, but just take me off, done. Cant do anything correct, So if I have another question pertaining to the switch wiring, I have to post another question, that would be more confusing for everyone, seems that everything on this is related as far as I can see, it all pertains to the CB/PA switch, where the wiring goes, and the wiring to the switch. Now how am I off topic, don't understand.
A picture of the board was sent to me, so I sent one back showing the wiring I had, was different, reason I posted picture of the board, to compare boards. I don't understand how it is off topic. Again, I don't have any information on these radios, thats why I asked for help, you have all the information, I give up, remove me, don't understand what I did to be off topic.

 

[Mark A Bradley]

This is the same radio. Sorry, did not know I was off topic, I needed the wiring for the switch, that's it. If you have issues with what I need, then I won't ask for help. Just remove me from the Forum, you have been very helpful, but if you are having issues with me, just remove me, I don't need help, it seems you have it in for me. I posted those pics to help you out, to make it easier for you, I thought a picture of the board may help you out with the switch, possibly a different board, as the wiring pictures pictures that were posted for me to see was different, that's how it got off topic, just asking for a simple where the wire go, as for where they go on the board, I can probably use another radio to find where they go, just needed the switch wiring. You saw the solder job, I was not sure if this was correct, as I have o other books or information on if this was a correct solder job or not. Seems that the radio wiring on some of the same radios are different, mostly the same, but where do you got get the correct switch wiring, cant find it on the internet, only seems that the Techs have all the information that a person may need, otherwise flying blind. Sorry, but just take me off, done. Cant do anything correct, So if I have another question pertaining to the switch wiring, I have to post another question, that would be more confusing for everyone, seems that everything on this is related as far as I can see, it all pertains to the CB/PA switch, where the wiring goes, and the wiring to the switch. Now how am I off topic, don't understand.
A picture of the board was sent to me, so I sent one back showing the wiring I had, was different, reason I posted picture of the board, to compare boards. I don't understand how it is off topic. Again, I don't have any information on these radios, that's why I asked for help, you have all the information, I give up, remove me, don't understand what I did to be off topic.