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Picked UP A Cobra 139XLR

could i align it myself??? because it is WAY off frequency. i sound like charley browns teacher on sideband "WAHBAHWAHBAHBAHBAH" ahh and unforgetable voice. something us sidebanders with broken radios know all to well. aint that right?
 
hi,

yeah, you can align it yourself if you have a frequency counter with a BNC on the front of it. (not a freq. display like the FC-390 etc...)

you will also need some special tuning tools for turning the coils.
DO NOT use a jewelers screwdriver for two reasons.
for one, it will cause the adjustments to be inaccurate because its metal.
second, the metal screwdriver has a high probability of cracking the core of the coil, creating a huge headache.
cheap and dirty trick is to use a filed down toothpick, but you can get the tools at rad shak usually.

if you have never done this before, i would recommend that you have someone with experience do it; and you should watch very closely.
after that, you can probably do it yourself.
having said that; i like to offer the info and let the individual make their own determination about their ability to do the work.
(do this at your own risk)

let the radio warm up for about 20 minutes before starting.
radio to ch. 19 AM mode. clarifier centered (dont move it!)

connect freq. counter probe to TP8 and PC board ground.
(TP8 is near the mode crystals)
adjust CT6 for 34.9850 MHZ
switch radio to USB mode. adjust CT4 for 34.9875 MHZ.
switch radio to LSB mode. adjust CT5 for 34.9825 MHZ.

turn mic gain all the way down, key the mic (stay in LSB mode)
and adjust VR9 for 34.9825 MHZ.

connect freq. counter probe to TP9 (near VR9)
radio to USB mode (ch.19)
mic gain all the way down. adjust CT2 for 7.8025 MHZ.

switch radio to LSB mode, key the mic, and adjust CT3 for 7.7975 MHZ.

that should do it!

best of luck,
loosecannon
 
Thank you for the info MR Loosecannon. I really appreciate it. However I think this is Slightly over my head. Making a mod to a nice working Radio. 10-4 no problem. but fixing and aligning a classic cobra. Ehh id rather leave it to the professionals.
i will give this info to my tech if he doesnt already know this. and besides i do not have a freq counter.
Thanks for the info loosecannon
Maybe ill catch ya out in Dx land.
 
hey bigred,
i have been calling on 37LSB for the last few days, but i never hear anyone on there.
i'll keep trying. im CDX410.

im acutally using my 139xlr as my mobile right now.LOL
i have it sitting on the passenger seat facing me.
it actually works pretty well, but slides around too much.

later,
loosecannon
 
loosecannon said:
if thats not the problem, the driver is a 2SC1306, which isnt made anymore, but you can replace it with a 2SC2166.
the final is a 2SC1307, but again, not made anymore. can be replaced with a 2SC1969, or an NTE236. (1969 preferred)
you must re-bias the final and driver when replacing either.
driver should be at 40mA
final should be at 70mA.


best of luck, great radio!
loosecannon
Click to expand...

i checked it and its the driver it is Down and out for the count. ill be trying to find a 2sc2166

keep trying for me out on 37lsb mostly im just 202 not really ever CDX202 Roger.

CYa
 
normally the clarifier adjusts only the receive frequency.
no matter where you set the knob; you are still transmitting on the same freq. which is set by an internal adjustment.

"unlocking" the clarifier, which used to be known as "tied together", modifies the clarifier circuit so that when the knob is turned, both the transmit and receive frequency is moved together.
so, wherever you adjust the clarifier knob, you are transmitting and receiving on that freq.

make sense?
loosecannon
 
loosecannon said:
normally the clarifier adjusts only the receive frequency.
no matter where you set the knob; you are still transmitting on the same freq. which is set by an internal adjustment.

"unlocking" the clarifier, which used to be known as "tied together", modifies the clarifier circuit so that when the knob is turned, both the transmit and receive frequency is moved together.
so, wherever you adjust the clarifier knob, you are transmitting and receiving on that freq.

make sense?
loosecannon
Click to expand...
THank you Sir !
 
Ok i put the 1969 in and now it outputs. and OMG a person told me it outputs better audio than my galaxy :shock: so thats cool, too bad i cant align it. but all in good time a guy in the local ham club has one so he said he could align it for me. or ill try to borrow a freq counter off of another club member. for the most part the Sara has a lot of nice people.
 
loosecannon said:
hi,

yeah, you can align it yourself if you have a frequency counter with a BNC on the front of it. (not a freq. display like the FC-390 etc...)

you will also need some special tuning tools for turning the coils.
DO NOT use a jewelers screwdriver for two reasons.
for one, it will cause the adjustments to be inaccurate because its metal.
second, the metal screwdriver has a high probability of cracking the core of the coil, creating a huge headache.
cheap and dirty trick is to use a filed down toothpick, but you can get the tools at rad shak usually.

if you have never done this before, i would recommend that you have someone with experience do it; and you should watch very closely.
after that, you can probably do it yourself.
having said that; i like to offer the info and let the individual make their own determination about their ability to do the work.
(do this at your own risk)

let the radio warm up for about 20 minutes before starting.
radio to ch. 19 AM mode. clarifier centered (dont move it!)

connect freq. counter probe to TP8 and PC board ground.
(TP8 is near the mode crystals)
adjust CT6 for 34.9850 MHZ
switch radio to USB mode. adjust CT4 for 34.9875 MHZ.
switch radio to LSB mode. adjust CT5 for 34.9825 MHZ.

turn mic gain all the way down, key the mic (stay in LSB mode)
and adjust VR9 for 34.9825 MHZ.

connect freq. counter probe to TP9 (near VR9)
radio to USB mode (ch.19)
mic gain all the way down. adjust CT2 for 7.8025 MHZ.

switch radio to LSB mode, key the mic, and adjust CT3 for 7.7975 MHZ.

that should do it!

best of luck,
loosecannon
Click to expand...

on the first TX test on TP8 the highest I can get it to go is 31.420 and it fluctuates down to 31.311..


on rx testing my freq counter seems fine. Its a bk precision 1803


any ideas? btw I am talking about a 139xlr
 
hello is this thing on?

Is this one of those times where a guy is screwed no matter what he does. I used the search function to look for answers. I came close. But i will get crap for firing up an old thread. Now if I start a new thread I will get crap from people because I didn't use the search function.

my issue is directly related to the alignment procedure for a cobra 139 xlr
 

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