Taiwan R.O.C. (Republic of China) radios came before the Philly made ones, they are much better quality than the later China made 148's.
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Cobra 148 GTL Common Mods Question
- Thread starter crash-harris
- Start date
That's good to hear. Took a 1.5 hour trip today and couldn't get anyone to answer a radio check on 19, but swear I got someone mocking my "break 1-9" yesterday. A few times today it seemed like the "brit/dim" switch didn't change anything. After getting pictures tomorrow, I'm thinking about restoring power to the Uniden CB in the retired truck and listening for this one to transmit to it. Hopefully pictures tomorrow will clear some things up!
Still no pictures. Audio, after all is AC. It has a small bit of DC with it but it's the AC portion of the signal that can cause what you're dealing with. Improper mic wiring or wire fraying in the connector like you said could cause the mic audio AC portion to creep into the speaker return path that the mic is closing when you PTT. Mics are a two part mechanism, TX audio and PTT. Break each part down when troubleshooting similar problems. Always easy to overlook the simplest of parts.
Sorry about pictures, they are on the agenda for tomorrow. Between it raining all day and a splitting headache I didn't get out to the truck. I did start fixing the Cobra 5 pin mic that was attached to the radio previously, but for the life of me I can't find a Cobra wiring diagram for the mic using the wire colors. I have a red, white, black, yellow and the shield. All the diagrams I've found either contain a blue wire or list the wires as TX, RX, etc, but don't elude to which color that wire might be. You'd think Cobra would have a readout for that since they made them (I know there is no industry standard for this).
you are going to find out most truck drivers do not answer a radio check. if they do they will just say I have mine etc. just saying break 19 for a radio check 99% will never come back. they best way is to just ask some thing in general or if you hear some one talking just reply to it or ask for directions or some thing of that nature. saying breaker 1 --9 for a radio check is some thing that was used in the 70's and 80's.
just some info for your future using of the radio. or just ask if you are over modulated that you just had some work done on your radio etc. one that will get you a reply in most cases is ask if some one knows what time it is. the other day a guy asked that and the driver said to turn the mic gain down. after the driver finished he had the guy asking this to turn down the mic gain until you just barely hear him. not all do this but some will do this to you.
just some info for your future using of the radio. or just ask if you are over modulated that you just had some work done on your radio etc. one that will get you a reply in most cases is ask if some one knows what time it is. the other day a guy asked that and the driver said to turn the mic gain down. after the driver finished he had the guy asking this to turn down the mic gain until you just barely hear him. not all do this but some will do this to you.
It's rate that I don't get a reply for a radio check around here, but I get what you're saying. There's just some people out in that wasteland...
Finally, the long anticipated pictures!
From left to right, top to bottom...
Front outside, rear outside,
bottom outside, inside board top (faceplate pointing right)
inside board bottom (faceplate still pointing right)...
From left to right, top to bottom...
Front outside, rear outside,
bottom outside, inside board top (faceplate pointing right)
inside board bottom (faceplate still pointing right)...
...top of the inner faceplate, bottom of inner faceplate,
bottom side of the board where the ext speaker and PA Jacks are located, backside of the speaker (could that be the resistor causing the talkback?).
All pics are clickable thumbnails. Looks like the extra wires on the top of the board are wired to the brit/dim and hi/lo tone switches. Anyone recognize any of these mods?
bottom side of the board where the ext speaker and PA Jacks are located, backside of the speaker (could that be the resistor causing the talkback?).
All pics are clickable thumbnails. Looks like the extra wires on the top of the board are wired to the brit/dim and hi/lo tone switches. Anyone recognize any of these mods?
The radio definitely has a Channel mod, you can see by the wires running to the PLL area if you look up close I would not be surprised if one of the traces was cut for the mod to happen.
Edit: Yup the trace by the black and pink wires has been cut. On the channel select board it looks like one of the resistors may have possibly been swapped out for an inductor, also I see what looks to be a little capator on the channel indicator module.
It's kind of hard to tell from the picture, but under the DC input jack the choke on the right side looks like it might be burned or the wax maybe has melted, that could be just the picture though. Also I don't normally see a configuration with the ceramic capacitors arranged like that on the Cobra 29 and 25 radios, I have never worked on a 148 though so it might be standard, I'd have to look at the schematic.
That radio is clean, it looks like someone removed all the factory solder flux. This leads me to believe the modification likely has been performed correctly, most times the "hacks" will not bother to clean the old flux.
Edit: Yup the trace by the black and pink wires has been cut. On the channel select board it looks like one of the resistors may have possibly been swapped out for an inductor, also I see what looks to be a little capator on the channel indicator module.
It's kind of hard to tell from the picture, but under the DC input jack the choke on the right side looks like it might be burned or the wax maybe has melted, that could be just the picture though. Also I don't normally see a configuration with the ceramic capacitors arranged like that on the Cobra 29 and 25 radios, I have never worked on a 148 though so it might be standard, I'd have to look at the schematic.
That radio is clean, it looks like someone removed all the factory solder flux. This leads me to believe the modification likely has been performed correctly, most times the "hacks" will not bother to clean the old flux.
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Well than, that's a bit more than I want to chew off to return it to a stock-ish radio. I guess I need to know what switch does what then and learn to use it. Having extra channels but still looking like 1-40 is very disorienting for me.
Does it look to you like both of the aforementioned switches individually switch to the extra channels?
Any ideas what combos of switches being up/down would have the radio operating on the normal 40?
Request pics as needed and I'll post them up. Anything for help figuring out how to operate this radio with the mods!
Does it look to you like both of the aforementioned switches individually switch to the extra channels?
Any ideas what combos of switches being up/down would have the radio operating on the normal 40?
Request pics as needed and I'll post them up. Anything for help figuring out how to operate this radio with the mods!
I'm going to go out on a limb and say that your radio has 40 uppers and 40 lowers this is the common modification to do with this style radio meaning you'll have 40 channels below the regular number 1 and you'll have 40 channels above the regular number 40.
If you are confident with a soldering iron I can instruct you on how to remove the channel modification whatever functions are attached to the switches that were used for this modification will have to be rewired to the factory configuration this takes a little more work because you have to understand what wires go where on what switch.
I can help you figure out what switch position will give you the standard 40 channels but this will require another CB radio or an RTL-SDR. (Or plenty time spent looking at the swiitches, & studying what the mod does)
This channel mod has been done before many times, & it is normally referred to as uppers and lowers, perhaps several forum members will have the knowledge regarding what is involved in performing this modification. You could always resort to performing a Google search to discover what a Cobra 148 Channel modification entails.
Even without another CB radio or a friend with a CB radio you could still determine what switch positions gives you the 40 channels that are standard, but it will take a little bit of guess work and some time when locals are talking or skip conditions are good. (Or plenty time spent looking at the swiitches, & studying what the mod does) 73
-LeapFrog, 10-10 On the side.
If you are confident with a soldering iron I can instruct you on how to remove the channel modification whatever functions are attached to the switches that were used for this modification will have to be rewired to the factory configuration this takes a little more work because you have to understand what wires go where on what switch.
I can help you figure out what switch position will give you the standard 40 channels but this will require another CB radio or an RTL-SDR. (Or plenty time spent looking at the swiitches, & studying what the mod does)
This channel mod has been done before many times, & it is normally referred to as uppers and lowers, perhaps several forum members will have the knowledge regarding what is involved in performing this modification. You could always resort to performing a Google search to discover what a Cobra 148 Channel modification entails.
Even without another CB radio or a friend with a CB radio you could still determine what switch positions gives you the 40 channels that are standard, but it will take a little bit of guess work and some time when locals are talking or skip conditions are good. (Or plenty time spent looking at the swiitches, & studying what the mod does) 73
-LeapFrog, 10-10 On the side.
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they just did the poor mans channel mods as most call it. you really need a freq counter to know what freq the switches put you on. just a cheap external counter will show you what freq you are on.
here is one version of the mod
http://www.cbtricks.com/members/cblincoln43/Poormans_Conversion.gif
here is a second version of the mod.
http://www.cbtricks.com/members/cblincoln43/Poormans_Conversion2.gif
there is a couple more versions but these are the most popular ones.
here is one version of the mod
http://www.cbtricks.com/members/cblincoln43/Poormans_Conversion.gif
here is a second version of the mod.
http://www.cbtricks.com/members/cblincoln43/Poormans_Conversion2.gif
there is a couple more versions but these are the most popular ones.
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I'm rather proficient with a soldering iron, however, I got those nubby fingers and no longer have the "extra hands" (stand and clips) that my fat fingers would need to not get burned. I'm totally fine leaving the mod, as long as I know how to use it, or at least run the radio normally. I got to eyeballing the switches last night and it looks like the CB/PA switch is involved as well. From what I can see, there is a bridge between the terminals on both sides of the CB/PA switch in the CB position, the LO position of the HI/LO TONE switch and the DIM position of the BRIT/DIM switch. I'm guessing in those positions I should be operating within the normal 40? Hopefully I can catch a day this week were I can restore power to the Uniden in my other truck, throw an antenna on and verify normal channel operation.
It's been cold and terrible out this week with freezing rain last night, but it's suppose to be in the 50's today before we take our little trip again. I'm planning on getting the radio back into the truck and I'm going to try to get power to the Uniden in the other truck to verify normal 40 channel operation. I also found some good info on Cobra 5 pin mics that I'm going to attempt to put to good use if I get the time today.
So does anyone see anything that would cause talkback inside the radio? The only thing I see is the thing soldered between the speaker leads on the speaker itself. I'm guessing that's probably supposed to be there, but not sure since I normally don't deal with single, small speakers.
So does anyone see anything that would cause talkback inside the radio? The only thing I see is the thing soldered between the speaker leads on the speaker itself. I'm guessing that's probably supposed to be there, but not sure since I normally don't deal with single, small speakers.