I found somewhere can not remember right off where but these were listed as good finals and drivers. Could some one tell me if these are or not and which ones you can use as driver or final. 2sc2132 ,2sc1307, 2sc1817, 2sc2166, 2sc2312, 2sc2314, 2sc1957. Started reading understanding and repairing cb radios and The screwdriver expert's guide by lou franklin. Found me 5 radios for free. cobra29 classic 05 model to experiment on. Thanks to my trucking buddies. there is a guy around here that works on cb's but is high dollar. One of my friends had him work on his radio and he told me he replaced a regulator, couple of diodes and a transistor for $60.00. I was talking to him on the cb and past each other so I did not get the low down on what was wrong with radio but don't that seem a little high. He thought so. thanks for the help guys I'm learning every time I talk on this forum. looking for a o-scope seen a tektronix 465 I think that was the number older model. would have to learn how to use it.
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cobra 29 & 25 driver's and finals
- Thread starter daddyo
- Start date
When one wants to change out to a better final, the simple, cheap solution is to put a MOSFET IRF-520 in there are change out a few parts to make the transition from a bipolar(stock) final to a Mosfet device. But one would need to make sure the AM Limiter and 54mhz coils are proper in the radio first.
The benefits? If properly peaked and tuned, they can produce a solid 30-35W. They are also very cheap, about $2.50 and can be found everywhere. Make your own biasing part for about $1/less. $6 for everything to do the job yourself.
http://www.worldwidedx.com/threads/cobra-29-with-irf510-irf520-erf2030-question.170400/
Also did it to a Cobra 148 with xlnt results; xlnt read too.
http://www.worldwidedx.com/threads/mosfet-conversions-for-upd858-and-mb8719-boards.95853/page-6
The benefits? If properly peaked and tuned, they can produce a solid 30-35W. They are also very cheap, about $2.50 and can be found everywhere. Make your own biasing part for about $1/less. $6 for everything to do the job yourself.
http://www.worldwidedx.com/threads/cobra-29-with-irf510-irf520-erf2030-question.170400/
Also did it to a Cobra 148 with xlnt results; xlnt read too.
http://www.worldwidedx.com/threads/mosfet-conversions-for-upd858-and-mb8719-boards.95853/page-6
Last edited:
yo daddyo,
here is a list for you:
2SC2312= final. can be substituted for the 2SC1969 and the 2SC1307. these are not made anymore, and most of the ones you find online are fakes. they are a great final, very robust, and will usually put out a watt or two more than a 1969.
2SC1307=final. can be substituted for the 2SC1969, and the 2SC2312. these are made of unobtanium and will not be found anywhere except inside an old 70's SSB cb. great final. again, if you find any online for sale, they are probably fake.
2SC1817=final. can be substituted for the 2SC1969, 2SC1307, and the 2SC2312. these were not used in too many radios, and have not been made in decades. good final, and usually puts out a watt or so less than its counterparts. you MIGHT find someone selling a NOS one of these, as they are not as well known. there are probably fakes being made of this one too.
2SC2166=driver. This was also used as a final in some AM cb radios in the 70's. great driver, and matches up well with any of the finals listed above. these can still be found online sometimes, but are still very rare. yes, there are fakes.
2SC2314=driver. very good driver and tends to push a few more watts out of the 1969 and its counterparts. this is the driver of choice when modding 25 and 29LTDs. not a drop in replacement for SSB gear.
2SC1957=driver. also a good driver, but doesn't put out quite as much as the 2314.
good for a driver in AM units like the 25 and 29, but is not a drop in replacement for SSB gear.
As Robb said, the IRF520 MOSFET is the go to replacement for AM radios these days for both driver and final, and gives a nice power boost to those radios.
it is also used in SSB gear, but they are not drop in replacements for radios with SSB unless the radio already came with them from the factory.
you will find instructions to do the change over in the older SSB radios, but they can be a pain in the butt to get right, so not usually recommended for the casual modder.
exit13 has posted great tutorials for using these mosfets in the older mb8719, and upd858 radios, but again, there is still the possibility of part value tweaking required.
no two radios are ever exactly the same.
You will find in your reading that Lou recommends some motorola drivers and finals as replacements, and they do work, but they won't deliver any more power than the stock transistors. those MRF transistors are also not made anymore and will be expensive.
as for the price of the repair, it could be a LITTLE bit high, but depending on how much troubleshooting was involved, it could also be a sweet deal.
repair prices are almost never based on how many parts are replaced, unless they are very rare, or in a case such as replacing all the electrolytic capacitors in an old radio.
it's the troubleshooting that you are paying for. who knows, some other guy may have found the bad regulator, replaced it and called it good. they may have charged less, but from the sound of it, the radio would have been back at the shop before too long.
the scope is imperative, but if it were me, i would start with a good watt meter, a good RF signal generator with a calibrated output level, and a good accurate voltmeter, both digital and analog. try to find voltmeters that will measure AC millivolts.
find the instructions online to build your own dummy load, because tuning other peoples' radios with your antenna can cause some confusing results sometimes.
you really want to know that you are tuning a radio to a load with no reactance and a true 50 ohm value no matter what frequency you are on.
that first chapter in the Understanding and Repairing book where Lou shows you what kinds of equipment you should have, and how to make some of it is pure gold.
follow what he says there.
hope this helps,
LC
here is a list for you:
2SC2312= final. can be substituted for the 2SC1969 and the 2SC1307. these are not made anymore, and most of the ones you find online are fakes. they are a great final, very robust, and will usually put out a watt or two more than a 1969.
2SC1307=final. can be substituted for the 2SC1969, and the 2SC2312. these are made of unobtanium and will not be found anywhere except inside an old 70's SSB cb. great final. again, if you find any online for sale, they are probably fake.
2SC1817=final. can be substituted for the 2SC1969, 2SC1307, and the 2SC2312. these were not used in too many radios, and have not been made in decades. good final, and usually puts out a watt or so less than its counterparts. you MIGHT find someone selling a NOS one of these, as they are not as well known. there are probably fakes being made of this one too.
2SC2166=driver. This was also used as a final in some AM cb radios in the 70's. great driver, and matches up well with any of the finals listed above. these can still be found online sometimes, but are still very rare. yes, there are fakes.
2SC2314=driver. very good driver and tends to push a few more watts out of the 1969 and its counterparts. this is the driver of choice when modding 25 and 29LTDs. not a drop in replacement for SSB gear.
2SC1957=driver. also a good driver, but doesn't put out quite as much as the 2314.
good for a driver in AM units like the 25 and 29, but is not a drop in replacement for SSB gear.
As Robb said, the IRF520 MOSFET is the go to replacement for AM radios these days for both driver and final, and gives a nice power boost to those radios.
it is also used in SSB gear, but they are not drop in replacements for radios with SSB unless the radio already came with them from the factory.
you will find instructions to do the change over in the older SSB radios, but they can be a pain in the butt to get right, so not usually recommended for the casual modder.
exit13 has posted great tutorials for using these mosfets in the older mb8719, and upd858 radios, but again, there is still the possibility of part value tweaking required.
no two radios are ever exactly the same.
You will find in your reading that Lou recommends some motorola drivers and finals as replacements, and they do work, but they won't deliver any more power than the stock transistors. those MRF transistors are also not made anymore and will be expensive.
as for the price of the repair, it could be a LITTLE bit high, but depending on how much troubleshooting was involved, it could also be a sweet deal.
repair prices are almost never based on how many parts are replaced, unless they are very rare, or in a case such as replacing all the electrolytic capacitors in an old radio.
it's the troubleshooting that you are paying for. who knows, some other guy may have found the bad regulator, replaced it and called it good. they may have charged less, but from the sound of it, the radio would have been back at the shop before too long.
the scope is imperative, but if it were me, i would start with a good watt meter, a good RF signal generator with a calibrated output level, and a good accurate voltmeter, both digital and analog. try to find voltmeters that will measure AC millivolts.
find the instructions online to build your own dummy load, because tuning other peoples' radios with your antenna can cause some confusing results sometimes.
you really want to know that you are tuning a radio to a load with no reactance and a true 50 ohm value no matter what frequency you are on.
that first chapter in the Understanding and Repairing book where Lou shows you what kinds of equipment you should have, and how to make some of it is pure gold.
follow what he says there.
hope this helps,
LC
Loosecannon, that sure helped me with the final and driver question. Been trying to make heads or tales out of which ones would be good together and where to get them. RF company has several for sale but I don't know if they would be fakes. I looked at the threads robb posted for me that helped a great deal also. But I can not find in the forum using the search engine on how to make the decreate part that was mentioned (biasing part) for the irf-520 mod. It listed parts but I would not know how to put them in series/paralle (excuse my spelling) I have a good volt meter and I am looking around for the rest of the equipment you mentioned. I think I can figure out how to use the signal generator / tracer etc. Scope would have no idea how to use it right off. I'm just learning as I go. You guys are a big help to me and I can not wait to get all parts together and try the irf-520 mod and a few others. BIG THANKS, DADDYO
anything you buy from RF Parts Co. will be the real deal. Merit the owner is the man.
yes, you will pay dearly for it, but it will work. the 25 dollar minimum order is a real deal breaker for a lot of people it seems.
as for the IRF520 conversion, here are the places you need to look:
http://www.cbtricks.com/miscellaneous/fet_papers/ekl/graphics/erf2030_cobra_29_mod.jpg
here is the info for building your own companion part:
http://www.cbtricks.com/miscellaneous/fet_papers/mosfet_experiment.htm
here is the page with all the schematics and service info:
http://www.cbtricks.com/radios/cobra/29ltd_29ltd_st_29wx_st/index.htm
a word of caution here. there are two different service manuals listed on this page, and one of them is wrong. its actually for the 25LTD.
for the 29LTD use the links that say "page 1-11, and page 12-34". not the all in one version below those. it can get pretty confusing if you try to use the wrong one and don't notice right away.
make sure to consult your books on proper power transistor replacement techniques.
good luck,
LC
yes, you will pay dearly for it, but it will work. the 25 dollar minimum order is a real deal breaker for a lot of people it seems.
as for the IRF520 conversion, here are the places you need to look:
http://www.cbtricks.com/miscellaneous/fet_papers/ekl/graphics/erf2030_cobra_29_mod.jpg
here is the info for building your own companion part:
http://www.cbtricks.com/miscellaneous/fet_papers/mosfet_experiment.htm
here is the page with all the schematics and service info:
http://www.cbtricks.com/radios/cobra/29ltd_29ltd_st_29wx_st/index.htm
a word of caution here. there are two different service manuals listed on this page, and one of them is wrong. its actually for the 25LTD.
for the 29LTD use the links that say "page 1-11, and page 12-34". not the all in one version below those. it can get pretty confusing if you try to use the wrong one and don't notice right away.
make sure to consult your books on proper power transistor replacement techniques.
good luck,
LC