It can be done but why waist the time and tear your gear? Heck people where doing that in the 1990's when I first got started. It was not a great idea then and it has not gotten any better. You can not just replace the driver and final and think you are going to see huge watts the Cobra 25 is not a 148 totaly different board with little in common.
I could pop a 1969 final in one of my PC122 clones I am never going to see the watts out of that chassis that my Old 148 made. Why? The rest of radio is not designed to drive the 1969 to it's full potential. In fact even with the stock final in the PC122 clones more then 15 watts and they live short lives because they can not dissipate the heat well enough so all the other parts inside the radio live short lives due to heat saturation and thermal runaway!
In case you do not know watts is a measurement of heat dissipation not really power. If I take a transistor that can dissipate 30 watts with just standing air conduction and I can cool it on demand rapidly like say a huge heat sink I can push that transistor past the it's rating up to the limits of the junctions at some point they will break down. I do not recall from H.S. if that magic temp is 150 or 180 F where they start to break down. So where is that larger transistor going to dump all the extra heat? IT does not matter if it is a 2SC1969 or a 2SC2897......
You can make it work you need to change the values of some caps and maybe a resistor or diode and re-bias the final and the driver but to what end?
If it is a decent amp and no more then 4 pills you should be able to drive it well enough with a single final radio. You should be able to use 1-2 watts dead key swinging to not more then 15 watts and drive any modest box that is cable of it to at least 250 watts.
You get the most bang with your first 100 watts if talking anything but local. I really do not need more then stock to talk localy unless you want to act like those guys on channel six. You next big leap does not really take place until you hit 500-600 watts. So if you are the type where being louder and more powerful then is needed stop now save your money until you can afford a 667 and be done with it for a while.
I see people all the time getting 300 watts out of the RFX-150 amp and it is just silly. That gear will not last that long tuned to with in every inch of it's life! Worst yet most people can not say no to more power so they will not run with it at a modest setting and just let it swing!
I always set my gear low so that I in a fit of stupidity which I am prone to like anyone else it is not practical for me to "turn it" because I would have to open my radio up and get the magic screwdriver out. I have never flown a final or a driver or an amplifier up!
My gear has saved my life twice and at least 7 times it kept me from getting a ticket on I75S and I95 and it has on more then one occasions helped me before we had GPS find where I was and how to get back to where I wanted to be. I can not even begin to count the hours of entertainment CB's have given me!
So get your gear properly aligned and repaired if need be. Get an amp that is twice as powerful as you think you want or need then let it idle and watch it last a long long time!
My Lincoln has a single MRF455 in it. It is about 16 years old and it has not once set foot in a shop. It has a huge aluminum heat sink that makes all they Magnum chasis amps in 75-150 range look gimp. It is not just the number of fins and surface area total mass has an impact as well. You know why? To dissipate the 65 watts that the transistor is rated for. IT would scare you to know how much power and heat it makes on SSB if I am rag chewing! Now imagine if it did not have that heat sink!!! For the record I never turn it up past 12 O'clock because I am a bag of hot air on SSB. LOL
I could pop a 1969 final in one of my PC122 clones I am never going to see the watts out of that chassis that my Old 148 made. Why? The rest of radio is not designed to drive the 1969 to it's full potential. In fact even with the stock final in the PC122 clones more then 15 watts and they live short lives because they can not dissipate the heat well enough so all the other parts inside the radio live short lives due to heat saturation and thermal runaway!
In case you do not know watts is a measurement of heat dissipation not really power. If I take a transistor that can dissipate 30 watts with just standing air conduction and I can cool it on demand rapidly like say a huge heat sink I can push that transistor past the it's rating up to the limits of the junctions at some point they will break down. I do not recall from H.S. if that magic temp is 150 or 180 F where they start to break down. So where is that larger transistor going to dump all the extra heat? IT does not matter if it is a 2SC1969 or a 2SC2897......
You can make it work you need to change the values of some caps and maybe a resistor or diode and re-bias the final and the driver but to what end?
If it is a decent amp and no more then 4 pills you should be able to drive it well enough with a single final radio. You should be able to use 1-2 watts dead key swinging to not more then 15 watts and drive any modest box that is cable of it to at least 250 watts.
You get the most bang with your first 100 watts if talking anything but local. I really do not need more then stock to talk localy unless you want to act like those guys on channel six. You next big leap does not really take place until you hit 500-600 watts. So if you are the type where being louder and more powerful then is needed stop now save your money until you can afford a 667 and be done with it for a while.
I see people all the time getting 300 watts out of the RFX-150 amp and it is just silly. That gear will not last that long tuned to with in every inch of it's life! Worst yet most people can not say no to more power so they will not run with it at a modest setting and just let it swing!
I always set my gear low so that I in a fit of stupidity which I am prone to like anyone else it is not practical for me to "turn it" because I would have to open my radio up and get the magic screwdriver out. I have never flown a final or a driver or an amplifier up!
My gear has saved my life twice and at least 7 times it kept me from getting a ticket on I75S and I95 and it has on more then one occasions helped me before we had GPS find where I was and how to get back to where I wanted to be. I can not even begin to count the hours of entertainment CB's have given me!
So get your gear properly aligned and repaired if need be. Get an amp that is twice as powerful as you think you want or need then let it idle and watch it last a long long time!
My Lincoln has a single MRF455 in it. It is about 16 years old and it has not once set foot in a shop. It has a huge aluminum heat sink that makes all they Magnum chasis amps in 75-150 range look gimp. It is not just the number of fins and surface area total mass has an impact as well. You know why? To dissipate the 65 watts that the transistor is rated for. IT would scare you to know how much power and heat it makes on SSB if I am rag chewing! Now imagine if it did not have that heat sink!!! For the record I never turn it up past 12 O'clock because I am a bag of hot air on SSB. LOL
