Cobra 139 no tx no rx

[radiocom215]

Help. My pa/cb switch has no power.
Lights up but nothing else.
Its 23 chan ssb.

Im not good at reading the schematic.
Can anyone please tell me where the power comes from and what voltage it should be?
I would really appreciate it.

 

[K4EET]

radiocom215,

I'm not quite sure what you are asking. Are you asking what voltage should you read at the PA/CB Switch (S3)? Or are you asking something else?

Cobra 139
Cobra 139

Cobra 139 Schematic
http://www.cbtricks.com/radios/cobra/139/graphics/cobra_139_sch.jpg

If you know, is a Cobra 139 the same as a Cobra 139XLR? There seems to be more information for the Cobra 139XLR on the Internet but that may be a different animal. Meanwhile, I'll try to determine if there is a difference.

Awaiting your response...

Cheers! Dave

 

[radiocom215]

I looked at 139xlr and the schem is different and I'm not good at reading these.
I have power now to the switch but no rx or tx.

I key the mic and nothing happens. No meter movement.

 

[ipfd320]

take a Piece of wire or a bent paper clip and jump out the pins on the mike jack if the tx lite comes on or if the receive starts working the its a microphone problem--if you jump out the pins and nothing happens then the finals took a crap

 

[radiocom215]

Hey, I really appreciate the help.

I just found the board is cracked at the right back corner.

Do you think it's possible to solder and connect those few circuits?

This makes me sick. Geez

 

[KC4RAF]

Yeah, you can solder the traces once you've scraped off the green (usually) insulation on them. Don't use too high a heat on the iron. I usually put a piece of very thin wire (~24 gauge) to help stabilize the board.
hth

 

[radiocom215]

Thanks for the help.
It doesn't seem to be easy scraping.
Im afraid of using too much pressure fearing I'll scrape the copper trace off.
I was planning on using telephone wire.
Is that too small?

 

[KC4RAF]

Telephone wire will be fine. I use a very small screwdriver or other decent pointed driver to scrape off the green. It does require a little bit of pressure to scrape; if you can get a finger under the board where it's cracked, will help when scraping.
BTW, you can use wire that is pretty much as wide as the trace, so don't worry too much about the size, (just as long as it's bigger than your hair!.)

 

[radiocom215]

Due to congested area and can't get a good scrape, if there are two different components on the same trace, couldn't I bridge the two pins?

 

[TheSpaceMann]

If you are having difficulties, you may need to just send the radio out for repairs.

 

[ipfd320]

yes you can solder from 1 component to the other on the same trace line with wire--i fixed a badly damaged radio from 1 side to the other on the solder joints

 

[KANE4109]

could you get into there with a dremel tool and a light wire brush? That might help...

 

[larbian]

That area is jammed with components and no room to get a dremel or anything down in so I bridged pins and the radio receives but when mic is pressed, the relay clicks but it does not transmit and doesn't interrupt the receive.
Probably something in my repair job but I don't know where to start.

By the way, how do you get the relay cover off. I used dental pics pushing and pulling on that tab but cant get it off.