148GTL SSB problem

[dss56]

So i received a 148gtl to add extra channels. As I always do I check out the radio first.

radio has been recapped
radio off frequency. Fixed
AM great power and clean audio.
LSB and USB has the dreaded dirty warble audio.
I cant lower the ssb power vr11 does nothing.
Also cant lower the AM power, seems like something has been modded to bypass am/ssb power.
Radio is spot on for frequency both AM and SSB
Receive is great. Just the bad audio on SSB.

Here are some pictures of a NTE36 mounted to the back of the radio.
Also if you transmit more than 30 seconds on SSB the back where the finals get real hot.

I called customer and he states he has had radio for 2 years with no problems.
Again radio has had a lot done to it and I hate radios like this as i dont know what was done just a visual.

Well there is some history of the radio and couple of more days and radio is going back if i cant find the problem.

Been searching the net for this problem. So im trying.

 

[BayouRadioAmplifier]

is this the made in China D version? got one here.
it was given to me. I posted my repairs here.
works great on SSB now.

check the voltage at PLL IC1-9 is it lower than 8 V?

the known problem is R130 10 ohm resistor on the blue
wire going down to the circuit board. Replace it with
a quarter or half watt resistor.

here:

Post in thread 'Finally! A practical use for the Cobra 148GTL-DEE'

Oct 26, 2024

Help needed for Cobra 148 NW ST

Okay, Apparently, when this rig went back to Cobra to get Factory Reconditioned, instead of changing out R130 like they should've, it appears the "geniuses" at Cobra installed a Mod consisting of a board labeled: KEPC-635-A, and says: "for 148nw latchup reset." The board consists of 2...

www.worldwidedx.com

read that post. it is the blue wire from that little board as pictured.
it goes to a 10 ohm resistor, to the main board. it needs to be changed to
higher wattage. that resistor fails, and the voltage to the 8719 drifts.
the PLL drifts... My "made in China" "D" version works great now.

• BayouRadioAmplifier

• 

 

[brandon7861]

Its definitely the china version. Thats the only reason to put the regulator on the back heat sync. The china version had a steel heat sync in the factory placement and steel is not good enough.

And I second Bayou's advice. I remember a discussion last year about that same resistor. If not that (which it almost certainly is), there is also technical service bulletin 10015

https://cbtricks.org/radios/cobra/service_bulletins/graphics/tsb_10015.pdf

 

[BayouRadioAmplifier]

yes, on my 148 there is a TIP3055 mounted on the back panel
for the modulator.

hey dss56 - check that the mod to make the receive RF gain adjusts the AM carrier
power. that is how the radio I got did it. so I put it back to stock,
and have 3.8 watts carrier.

and adjust the bias to the RF amp section.

I turned off the AMC and ALC and just turn the mic down a little.
sounds great. looks great on the-scope. Plus sometimes I feed a Palomar
type amp with it. 120 W PEP out.

 

[dss56]

Seems replacing R130 and adjusting the bias helped a lot. I have been talking on the radio and no ssb audio complaints. Thanks for all the help.

 

[somicide]

View attachment 71945

for future reference, if anyone ever sees it mounted to the wall like this then its 100% from china or taiwan. its unmistakable and cannot be missed. i dont run a cb shop or anything but i refuse to touch these radios, specifically, because of how unpredictable they are compared to "normal" (read: philipines, malaysia...)148s

glad you fixed it, peace