The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

i have a cobra 148 gtl with the mb8719 pll chip in it. it is locked on transmit both am an ssb. any suggestion?

Check to see that someone has not replaced TR38 and installed it wrong i have seen this happen and cause this problem. If the driver has not been replaced and is installed correctly check the keying transistor it may be shorted not sure what the TR number is right off maybe Rick or someone will chime in and give the correct number hope this helps.

I checked tr38 it is ok i am prety sure its the keying transistor.. but don't know the tr number.

TR38 is the 2sc2166 driver the keying transistor is located toward the front of the radio hopefully some one will get the number for you if not i will try and look it up for you tonight.

ok thanks . when ever you get a chance.

Try checking TR21 voltage in RX b. 0.24v c. 2.99v e. 0v and in TX mode b. 2.55v c. 1.87v e. 0v. If the volts are ok check TR22 and TR23.

I checked tr21 22 23 with a transistor checker they are ok.. radio is still keyed up all the time

Is the fault still there even when the mic is not connected to the radio?

yes it is doesn't matter if the mike is pluged in or not

As you have given very little information has to which model of Cobra 148GTL, I will assume that this the model with the voltage regulator IC4 bolted to the side of the chassis if this is so.
First try removing TR35, if it stops transmitting then replace TR35 with a new transistor, if it is still stuck in the TX mode unsolder Pin 8 of IC4, if it stops transmitting then replace IC4 (MB3756).

Rick I tryed what yo said an it stayed keyed up untill i unsoldered pin 8 of ic 4... so I am replacing it when i find the part...hopely soon..well let you know what it does....thanks alot.

I replaced ic 4 ..... radio works fine now.... thank you Rick