Question about Ranger SS-3900 240-Channels Base CB Radio

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Hi . Have Cobra 148..But the Driver tx transistor. as normal bias curant 50ma but the 1969 as none when the preset is adjusted .

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wcrave

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The 1969 is probably bad. Replace it.

Posted on Jun 29, 2011

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Have a cobra 148 boughtat local market d expect much told it was a fm rig so i have recieve i have a reverse tx key it is uniace mic 4 pin a question of reversing tx pins in mic many thanx martyn


Go to www.cbtricks.com go to radios and schematics then go to C look for Cobra look for 148 then from there get the mike wiring diagram and you should be in business.

Nov 23, 2016 | Cobra Radio Communications

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This sounds like a problem with the MB3756 Regulator IC. It controls voltage regulation and TX/RX Switching. It is a common failure in these radios. Check voltages with schematic that can be found at
CB Tricks Home Page

Sep 02, 2013 | Cobra 148 GTL 120-Channels Base CB Radio

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My cobra 200gtl has no transmit


hi More than likely your pa transistor has blown have you checked it with a power meter if so r you getting the red tx led when the ptt is pressed if so then your problem lies with the rf transistor
replacing rf transistor

Jan 18, 2011 | Cobra 200 GTL DX 4-Channels Base CB Radio

1 Answer

148 cobra with no modulation


possably corrosion on the pins of the plug into the radio, unscrew, push in and out a couple of times, and try again, maybe a break in the cable where it flexes the most. or faulty antenna

Oct 23, 2009 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Cobra 148GTL can't TX on USB


Its the cap that feeds the first transistor to the first of the finals. It is either shorted or burned out.

Or the audio IC. It could be putting just enough out on AM to seem like its working, and then not enough for side band.

look at the caps near the finals. Look for a burn one, or one that could be twisted, or shorted in any way.

May 01, 2009 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Low TX PWR/ATU won`t tune. No SWR and ALC metwr reading?


You've replaced the pre driver, the drivers and finals. Set bias and still low output. The pre driver is the same transistor used as the tx exciter transistor on other pcb chassis on bottom of radio. Follow the gray coaxial wire from the pre driver on the RF circuit board back to the tx/rx i.f. Circuit board. The gray coax cable plugs right next to the tx exciter transistor on this pcb. Again it's on a different pcb all together and on the bottom of the radio and also. Replace it! And check for open bias or emitter to ground chip resistor next to it. You will get your drive back. Very few rigs have I seen the actual Finals blown in the mosfet or the bipolar version. Just the driver stage with a week pre driver and the SMT "pre" pre driver on the same RF pcb. And the tx exciter on the other pcb.

Apr 24, 2009 | Computers & Internet

2 Answers

Cobra 148fgtl low power on am/ssb no swing all finals ok


try adjusting the L36,L38 to the highest reading on the external meter and then adjust VR10 TO 4 watts. If this doesn't cure the problem, you have a weak final transistor. Good Luck

Feb 06, 2009 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Cobra 148 GTL steady tone though speaker


try rerouting your coax cable and make sure it's long enough

Jul 07, 2008 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

No am power


Radio dude, What you have is a blown am regulator. The sideband side does not use the mentioned transistor. They use a few different numbers here for the am regulator. One of them is a 2sc1419. On the Uniden Grant they put the transistor on the rear right above the antenna jack. On the 148 they put the transistor back in the right rear of the radio as your looking inside on the speaker side. Fixing it includes unsoldering the transistor and purchasing a replacement and resoldering it back in. This transistor is bolted to the side rail in the rear. I usually use a ECG152 as a replacement. It's not unusual to blow this one if the radio has been tuned. Let me know if your comfortable swapping it out. Otherwise it needs to go to a shop with a decent tech that won't take you to the cleaners. Let me know,, Mechanic

Feb 20, 2008 | Cobra 148 GTL 120-Channels Base CB Radio

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