Uniden PC68XL problems

[jetcracker82]

I'm new to this forum but not new to "radios". I am a communications tech for the Marine Corps. However I am new to working on CB's. I have a PC68XL that I've had for years. I was running it in my Jeep for a while. The jeep went down for a while and the radio sat pretty much the whole time. The jeep is back up and running but the CB isn't.

The radio will power on and I can rcv ok. It's not great but I can rcv and there is no meter deflection. I have no xmt and no meter deflection. The TX light goes from green to red when you hit the PTT. I don’t have schematics so I really don’t know where to start checking. I do have access to spectrum analyzers and o scopes as well as freq counters. I’m Navy certified in micro miniature soldering so any repairs I can do myself and do them properly. Any input would be helpful or common faults. I have done a visual inspection and didn’t see anything that looked suspect. No broken solder joints or toasted components. I even tried pushing on the board in different places to see if it was an intermittent problem, no luck.

I look forward to chatting with you guys and I might even see you out on the trail.

Thanks, Graham

 

[nobody]

Have you checked the antenna system and or microphone?

 

[mackmobile43]

Look for dry solder joints on the circuit board, use a plastic probe and just poke around.

Heating and cooling weather conditions are common causes to this.

 

[jetcracker82]

Have you checked the antenna system and or microphone?

Look for dry solder joints on the circuit board, use a plastic probe and just poke around.

Heating and cooling weather conditions are common causes to this.

I haven't done a ohm check on the RF cable. It looks fine though, no breaks or cuts. I will check that again. However, even if the ant and RF cable were bad wouldn't I still get some meter deflection?
I have looked over the board and I even poked around on it. All the solder joints looked good. If anyone has a source to some schematics that would make my life much easier.

 

[nobody]

I haven't done a ohm check on the RF cable. It looks fine though, no breaks or cuts. I will check that again. However, even if the ant and RF cable were bad wouldn't I still get some meter deflection?
I have looked over the board and I even poked around on it. All the solder joints looked good. If anyone has a source to some schematics that would make my life much easier.

Try another microphone and see if that works.

 

[443]

You talking about the meter in the radio is not "moving". Probably just stuck from sitting up. Take the cover off and tap on the meter a few times, may free it up, if not, may need a new meter, you can buy them online at Copper Electronics I think, or just rob one from another radio. Sometimes there is a screw you can loosen up on the meter and it will free it up, only need to turn it a hair sometimes and it will free up, I guess it sticks from corrosion buildup or something after sitting up for a while.

 

[Robb]

If you are getting normal receive into the radio and the meter isn't moving; then a replacement meter may be necessary. I buy my replacement meters from eBay. About ~$10 shipped. After replacing the meter, re-adjustment of the receive and transmit meter movements is often necessary; but not difficult to do. Getting the old meter out and replacing it with the new isn't too difficult either.

Most common problem with the output failure of these radios is the final transistor. Less often, it is the driver transistor. IF the final is gone; then get an Eleflow CB-20/2SC1969 transistor ONLY. ALL of the other 2SC1969 transistors on the market are made in China and are bonafide FAKES!!!
Real one:
http://rover.ebay.com/rover/1/711-5...0001&campid=5336136228&icep_item=220929737153

Or you can put a MOSFET IRF-520N or ERF-2030 and have more output power
Info here:
http://www.cbtricks.com/miscellaneous/fet_papers/index.htm

Ebay meters are fine and safe to buy; 2SC1969's transistors aren't unless they are the Eleflow's.

Made that mistake myself - just once . . .

Watch:

2SC1969 replacement with CB20W.avi - YouTube

MITSUBISHI 2SC1969 / ELEFLOW 2SC1969 (CB-20W) RF TRANSISTOR COMPARISON TEST. - YouTube