Newer Cobra 148 GTL

[tuner]

Hi guys , just looking for opinions on the new 148 GTL's that are available. Are they as good and solid as the older models? Any input would be greatly appreciated. Thanks

 

[sonoma]

they work fair on AM but on ssb some are terrible. not as good as the older side mic radios. one common problem is warrble on SSB and a 10ohm resister feeding the PLL burns out a lot until you upgrade it to a 1/2 watt. cobra even has a service bulletin on this item.

here is the resister bulletin
http://downloads.cobra.com/CB/TSB/TSB10002.pdf

here is a bulletin on the warrble.
http://downloads.cobra.com/CB/TSB/TSB10015.pdf

this does not fix it in most cases. this is just a couple documented items the 148 has that cobra will own up to. hope this helps. the side mic radios are a lot better if you could find a good used one. they just keep on working. the phillipin built ones seem to be the best.

 

[tuner]

Very Cool thank you !

 

[Robb]

Hey sonoma;

Are there any more links about this radio and part replacements that you know about? I've got one of these 148s that has gone belly up. Sure would like to fix it and get rid of it; or even keep it if it can be fixed satisfactorily.
Thanks.

 

[sonoma]

Hey sonoma;

Are there any more links about this radio and part replacements that you know about? I've got one of these 148s that has gone belly up. Sure would like to fix it and get rid of it; or even keep it if it can be fixed satisfactorily.
Thanks.

that info came from cobra . there is a link to all the info on the radios that they have. has schematics and service manuals. plus cbtricks.com has alot of the manual items for it. I will put the cobra link here for you to look at what they have.you might list here what the radio is doing and what you have checked so far and some one may have a idea as to what to check next to try to fix it. I guess you have a scope and freq counter to test the radio with plus a signal generator.


Cobra Technical

 

[sonoma]

if you have one of the new ones the 10 ohm resister feeds the PLL and if it shorts from the heat it will shut the radio down. that has been a big problem on the newer ones.

 

[RatsoW8]

Please do a search. There have to be at least a half dozen posts on this forum asking the same question about the new 148 GTL and the ensuing debate.

 

[sonoma]

Hey sonoma;

Are there any more links about this radio and part replacements that you know about? I've got one of these 148s that has gone belly up. Sure would like to fix it and get rid of it; or even keep it if it can be fixed satisfactorily.
Thanks.

here is a page I found some where awhile back and I have not seen one of this radio to see if this works. hopefully it will load here.

COBRA 148 MALAYSIA WARBLE MODS.


The nominal Uniden design has the power supplied to the audio section of the radio run through a large choke to filter stray RF out of the audio section.* The power that supplies the MB3756 comes directly from the DC jack in the back of the radio.*

The Malaysian 148s have the totality of the 13.8v input run through that big choke on the board (that looks like a transformer by VR10).* This works fine in a stock radio, but when you open it up, the additional current draw through that choke can cause a voltage drop.* This, in turn, plays havok with the PLL and is what leads to the FM condition (the warble) across the PLL.*

The modification involves returning the design to the Uniden design, thankfully this is easy to accomplish.* First, you will notice that there is a marking (with holes drilled) for a J44, but there is no shunt soldered across it.* Second, you will notice that there is a continuous trace between pin 1 on the TA7222P and pin 2 on the MB3756 (pin 2 on this is the +13.8v supply line).* The jist is that the MB3756 gets its power from pin 1 of the TA7222P, which draws power through that choke.*

You will see a spot along this trace that is thin (and on a Uniden radio, there is no copper at all there).* Scrape that copper off, you don't need to get it perfect, just ensure there is an interruption of continuity there.* Now, solder a wire onto the two holes for J44- this will supply line power to the MB3756 (replacing what you took away by scraping the trace off).*

Now, the only thing running through that choke is the power for the audio section - the rest of the radio now gets its power from the jack, just as Uniden designed.

Check C181 and C172* and replace with ones with a higher a working voltage.

they're the same part number on the Malaysia units as the older ones, D35 if i remember right, however on the Malaysia units when you look where D35 should be all you find is empty holes, thats because they used a junky surface mount varactor on the trace side, just remove it, and put a good varactor from a junker in the holes on the parts side where it belongs,


always use an ECG612 A.K.A. NTE612 varactor diode instead of those junky ones (bought in mass and on the cheap).* These diodes are frickin' tough, and worth the wait....over the mail and ect.* I very strongly suggest you order this diode instead of doing a "parts pull".

The factory part numbers are 1S2687D, 1S2687 or 1S2686.

not sure who wrote this up but it makes a lot of sense as far as repairing the radio for this

 

[sonoma]

hey Robb, is this some of the type info you was wanting for the newer cobra 148gtl. I listed all the main stuff I had for it.