Cobra 139-XLR Aligment info needed

[kb6led]

Anyone by chance have the complete alignment info for both the TX and RX for the cobra 139xlr? the receiver on this radio is a bit numb and want to go through the whole thing.

Thanks

 

[radiohobby]

Ok just spotted this post and getting tired but if I understand correctly the 138xlr mobile is the same as the 139xlr base. I have the manual for the 138xlr and here is the info for the synthesizer. I will post the rest tomorrow if you haven't already gotten it before then.
synthesizer alignment
Input of RF vtvm or O-scope to tp6 ch 1 AM Clarifier midrange adjust L24 for maximum output
Input of DC meter to tp7 ch 1 adjust L17 for 2.0 volts
Input of RF vtvm or O-scope to tp8 ch 19 AM Clarifier midrange adjust L16 for maximum output
Input of frequency counter to tp8 ch 19 adjust CT6 for 34.9850 mhz +/- 20hz
Input of frequency counter to tp8 ch 19 USB adjust CT4 for 34.9875 mhz +/- 20hz
Input of frequency counter to tp8 ch 19 LSB adjust CT5 for 34.9825 mhz +/- 20hz
Input of frequency counter to tp8 ch 19 LSB XMIT adjust VR9 for 34.9825 mhz +/- 20hz
Input of frequency counter to tp9 ch 19 USB Xmit adjust CT2 for 7.8025 mhz +5hz/-0hz
Input of frequency counter to tp9 ch 19 LSB XMIT adjust CT3 for 7.7975 mhz +0hz/-5hz

 

[kb6led]

That is helpful info to get in on frequency, but do you by chance have the complete receiver tune up info? The main problem is the receiver has poor sensitivity.

 

[loosecannon]

the coils to align for the receiver are L8, L7, L6, L5, L4, and L3.

i think L3 is the dual can and it can be balanced for even sensitivity on 1 and 40.

VR2 is the SSB AGC control and it can be increased, but if you go to far you will be generating too much internal noise.

VR5 is the AM AGC and the same rule holds true.
LC

 

[radiohobby]

The book says to set the radio on usb ch 19 with a signal gen set at 27.186 with no modulation at .25uv through a .01uf cap into the antenna jack and put a voltmeter on the speaker terminals and adjust L8,L7,L5,L4,L3 for maximum with the clarifier set at midrange.

 

[kb6led]

Perfect!! thanks for the information guys. Yeah the receiver needs some attention I am measuring about 3uv @ 10db sinad not very sensitive, a local guy brought me the radio to take a look at for him it will be nice to get it done and off the bench. Thanks again.