148 nw ssb problem

[blueridge]

got a 148nw with overheated am regulator. changing that and now or always the ssb is muffled and you can't make out what you're saying. the AM has good carrier and modest swing. any ideas what is making the sideband so low? There is also a hot spot on the board at L501, C501 and I assume R501 but I can't find a schematic. the resistor is burnt and I can't read the value, any ideas? the NW will not get very bright either but that may be a topic for a different day

 

[Radio Tech]

How did SSB sound before you had a problem?
It is my findings that the new 148 is not good on ssb. Reason is I have tried 4 out on the bench and found the same results.

Cobra was cutting cost and had the lastest builder leave out the 5 pin regulator and replace it with a cheap regulator circuit. This causes the voltage to change with modulation, making it unusable on ssb.

 

[loosecannon]

what kind of power supply are you using?
how many amps?

do other radios work ok on this power supply?
LC

 

[Switch Kit]

How did SSB sound before you had a problem?
It is my findings that the new 148 is not good on ssb. Reason is I have tried 4 out on the bench and found the same results.

Cobra was cutting cost and had the lastest builder leave out the 5 pin regulator and replace it with a cheap regulator circuit. This causes the voltage to change with modulation, making it unusable on ssb.

Agreed ! Sorry Blueridge.......sad but true dude. Here's some why for you.
COBRA RADIOS & MODIFICATIONS

 

[blueridge]

Agreed ! Sorry Blueridge.......sad but true dude. Here's some why for you.
COBRA RADIOS & MODIFICATIONS

i do have another 148 nw st and it seems to work fine. not a powerhouse but usable. it seems there is voltage where there shouldn't be on IC1 and crazy voltages elsewhere. I use an Astron 50 amp rack mount that drives everyhting else I have so I'm sure that's not the problem. After some tinkering it seems that if I whistle really loud or talk really loud I can start to clarify myself in on another radio. the clarifier on the NW does nothing, but it hasn't been unlocked either. On upper sideband channel 19 what should a frequency counter read? On AM it's dead on though i'm sure it needs a tuning to set some voltages.

 

[blueridge]

got a 148nw with overheated am regulator. changing that and now or always the ssb is muffled and you can't make out what you're saying. the AM has good carrier and modest swing. any ideas what is making the sideband so low? There is also a hot spot on the board at L501, C501 and I assume R501 but I can't find a schematic. the resistor is burnt and I can't read the value, any ideas? the NW will not get very bright either but that may be a topic for a different day

found the resistor value... it is a 10 ohm 1/4 watt. My other 148 doesn't even have the right value.

 

[Switch Kit]

I've heard those on AM without a problem Blue , as far as SSB is concerned , they will work OK , but if you are mainly a SSB'er it will not take you long to figure out there just not kosher compared to the older models and other cb SSB radios on the market today. The link I sent you and what Radio Tech mentioned is pretty much it in a nut shell for those.

I have yet to ever hear a fix when it comes to those radios and SSB , the radio was designed without some of the main parts that made the orignal 148s one of the best of it's times. It's really a crying shame that Cobra would let something like that happen to apparently cut costs ? There 25s and 29s are still pretty good after 30 some years of production.

 

[blueridge]

now I would like to get it working so I can sell it and get another REAL 148. I noticed today that when I touch either side (- or +) of a capacitor it starts to modulate on AM quite well. The cap is located near TR41 the AM voltage regulator. Not sure what this means. I replaced the cap and several surrounding but nothing new. I can key up with 3 watt carrier and barely make it to 3.5 watts, touch the cap and it goes back to DK 4 and swing about 8 which looks good on power meter but there is no RMS swing at all. Any ideas so I can get this junk off my lawn.

I've heard those on AM without a problem Blue , as far as SSB is concerned , they will work OK , but if you are mainly a SSB'er it will not take you long to figure out there just not kosher compared to the older models and other cb SSB radios on the market today. The link I sent you and what Radio Tech mentioned is pretty much it in a nut shell for those.

I have yet to ever hear a fix when it comes to those radios and SSB , the radio was designed without some of the main parts that made the orignal 148s one of the best of it's times. It's really a crying shame that Cobra would let something like that happen to apparently cut costs ? There 25s and 29s are still pretty good after 30 some years of production.