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Cobra 29 High Power mod with 2sc1969 transistor
- Thread starter Moleculo
- Start date
I've tested 2SC1969, 2SC1307, 2SC2312 to destruction .
I have never seen any useful power over 18W for any significant period of time with anything close to acceptable IMD or even approaching a linear amplification characteristic.
If you want more from a 29* Talk to Nomad about a peel and stick carrier control and buy, build, bowwow, steal a broadband 2 device BJT amplifier. A 2SC2290/2SC455 pair will accept 4W a 2SC454 pair a bit more and the 2SC2879 still more but do read the data sheet.
As for RM- Spaghetti and their fustercluck of plastic cased FET's of dubious origin you are on your own. In the time it took to write this 4.5 more of them died an instantaneous death due to force feeding their input with a steroid saturated radio.
There is one easy way to get a few watts out of many radios if you actually understand RF I/O .
Yes it's a HR-2510. So what ? It's driven with a 2SC2166 as well. It does have somewhat more heatsink area than a '29 but if you're doing these hotrod mods you already installed some sort of additional heatsink. (you did , didn't you? )
Oh ? You can't find 2290's, 455's, 454's 2879's or even the 2SC1969 anymore? (at least not reliably and economically)
Welcome to the new century. You have about 20 years of catching up to do.
TANSTAAFL
MosFets, LdMos, and a correctly aligned dilithium matrix are the new millennium boys and girls. Get on board or get left behind....
I have never seen any useful power over 18W for any significant period of time with anything close to acceptable IMD or even approaching a linear amplification characteristic.
If you want more from a 29* Talk to Nomad about a peel and stick carrier control and buy, build, bowwow, steal a broadband 2 device BJT amplifier. A 2SC2290/2SC455 pair will accept 4W a 2SC454 pair a bit more and the 2SC2879 still more but do read the data sheet.
As for RM- Spaghetti and their fustercluck of plastic cased FET's of dubious origin you are on your own. In the time it took to write this 4.5 more of them died an instantaneous death due to force feeding their input with a steroid saturated radio.
There is one easy way to get a few watts out of many radios if you actually understand RF I/O .
Yes it's a HR-2510. So what ? It's driven with a 2SC2166 as well. It does have somewhat more heatsink area than a '29 but if you're doing these hotrod mods you already installed some sort of additional heatsink. (you did , didn't you? )
Oh ? You can't find 2290's, 455's, 454's 2879's or even the 2SC1969 anymore? (at least not reliably and economically)
Welcome to the new century. You have about 20 years of catching up to do.
TANSTAAFL
MosFets, LdMos, and a correctly aligned dilithium matrix are the new millennium boys and girls. Get on board or get left behind....
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If you put 30 Volts onto the collector supply of a 2SC1969 you'll see a 40 or 50-Watt carrier.
But don't blink, because it won't be for long. And only if the output circuit has been tweaked to match the lower collector impedance this brings about.
The positive peaks of your modulation audio can reach 30 Volts peak in a radio that delivers that much audio power to the final's collector circuit.
The mid-1990s Superstar 3000 model used a single 2SC1969 with push-pull pair of 8-Watt audio power chips feeding a really large modulation transformer.
Did an honest 50 Watts PEP. Until you blew out one of the two audio-power chips.
Or that big modulation transformer. It was a hot rod, and would end up smashing into the track barrier from time to time.
The Cobra 29-type radios with the audio voltage stepped up by the modulation transformer will be limited by the audio power available. The 2SC1969 can do things that the rest of the radio may not have the gumption to make it do.
73
But don't blink, because it won't be for long. And only if the output circuit has been tweaked to match the lower collector impedance this brings about.
The positive peaks of your modulation audio can reach 30 Volts peak in a radio that delivers that much audio power to the final's collector circuit.
The mid-1990s Superstar 3000 model used a single 2SC1969 with push-pull pair of 8-Watt audio power chips feeding a really large modulation transformer.
Did an honest 50 Watts PEP. Until you blew out one of the two audio-power chips.
Or that big modulation transformer. It was a hot rod, and would end up smashing into the track barrier from time to time.
The Cobra 29-type radios with the audio voltage stepped up by the modulation transformer will be limited by the audio power available. The 2SC1969 can do things that the rest of the radio may not have the gumption to make it do.
73
Manufacture data sheets are not the end all to transistor output.
Most show the device at 12 volts and in a test jig that has not been optimized to get max output from the device in question.
Nomad is quite correct that the 1969 is capable of much more than what most think.
There was a radio built by ranger that also was a " hot rod" on AM mode the RG 33.
This radio used two audio ic's in push pull and was a real monster when tuned right.
If I rember correct I think the TRC 448 also used this type of 2 device push pull set up to achieve some nice output on AM mode.
73
Jeff
Most show the device at 12 volts and in a test jig that has not been optimized to get max output from the device in question.
Nomad is quite correct that the 1969 is capable of much more than what most think.
There was a radio built by ranger that also was a " hot rod" on AM mode the RG 33.
This radio used two audio ic's in push pull and was a real monster when tuned right.
If I rember correct I think the TRC 448 also used this type of 2 device push pull set up to achieve some nice output on AM mode.
73
Jeff
the RG 33 is basically the same radio as the 3000.
i have one that ive been messing with for a couple of years.
still not right, but i have to wind the modulation transformer again.
one of these days...
LC
i have one that ive been messing with for a couple of years.
still not right, but i have to wind the modulation transformer again.
one of these days...
LC
Agreed and kinda my point. Nitro engine that you rebuild every 4 seconds or a healthy daily driver. Daily driver of course means different things to different people.
I see several directions this can go in, so I'll try to go answer the OP question that "re-awakened" this thread.
You wanted to know the differences between the 2166 1969 pairings versus the 2314 1969 pairings and what was the differences.
Well, they are subtle - mostly by the power curve out of one, to meet the input requirements for the other.
So if your question is about replacing the Driver a 1907 - with a 2314 versus a 2166 and why?
Well, a lot of this has to deal with the simplicity of the mod conversion.
Some has to deal with gain, yes...but other factors of impedance as well as board layout to even make it workable comes into play.
Which in light of the above sentence - "PLAY" is the keyword here.
Take a radio that say, uses a 2166 - like an older radio of 1990's vintage - a 538W - you'll see it uses a 2166 for a final and produces quite a bit more in PEP than you'd expect a driver to do.
Hence the problem - on that same chassis - you can take out that 2166 - put in a 1969 final and change a cap from 220pF to 470pF and rework the output network coils. What you get is a wildly swinging radio that is ABSOLUTELY HILARIOUS to watch on a Meter, or the Receivers meter and the audio from it - contains nearly all audio and carrier simply follows it. The precursor of the mess we are in now...
But if you can obtain the Datasheets of the parts in question you'll see that their "Test Jig Circuits" they used to obtain the mess of charts afterwards in the sheets - you'll see that they expected it to do this - under these conditions.
So if you change the conditions - Meaning Not Voltage OR Current - but the circuit it is used in, like drop the part in, to replace another you blew up, and you find it seems to work ok, but curiosity hasn't killed you or your pet cat yet - we find the part, paired up with some minor changes to the components both upstream and downstream from it, can do some truly astonishing things that no one had predicted.
So if that is your question - again, in subtle ways, the part it replaces in the circuit provided - it can perform and in some cases - can be made to be idealized (work beyond your expectations) for the very process you wished to accomplish.
You wanted to know the differences between the 2166 1969 pairings versus the 2314 1969 pairings and what was the differences.
Well, they are subtle - mostly by the power curve out of one, to meet the input requirements for the other.
So if your question is about replacing the Driver a 1907 - with a 2314 versus a 2166 and why?
Well, a lot of this has to deal with the simplicity of the mod conversion.
Some has to deal with gain, yes...but other factors of impedance as well as board layout to even make it workable comes into play.
Which in light of the above sentence - "PLAY" is the keyword here.
Take a radio that say, uses a 2166 - like an older radio of 1990's vintage - a 538W - you'll see it uses a 2166 for a final and produces quite a bit more in PEP than you'd expect a driver to do.
Hence the problem - on that same chassis - you can take out that 2166 - put in a 1969 final and change a cap from 220pF to 470pF and rework the output network coils. What you get is a wildly swinging radio that is ABSOLUTELY HILARIOUS to watch on a Meter, or the Receivers meter and the audio from it - contains nearly all audio and carrier simply follows it. The precursor of the mess we are in now...
But if you can obtain the Datasheets of the parts in question you'll see that their "Test Jig Circuits" they used to obtain the mess of charts afterwards in the sheets - you'll see that they expected it to do this - under these conditions.
So if you change the conditions - Meaning Not Voltage OR Current - but the circuit it is used in, like drop the part in, to replace another you blew up, and you find it seems to work ok, but curiosity hasn't killed you or your pet cat yet - we find the part, paired up with some minor changes to the components both upstream and downstream from it, can do some truly astonishing things that no one had predicted.
So if that is your question - again, in subtle ways, the part it replaces in the circuit provided - it can perform and in some cases - can be made to be idealized (work beyond your expectations) for the very process you wished to accomplish.
back in the late 90's I use to change out the final on a cobra 29 for a 1969 and put a 1957 I think it was for the driver. I would change out a resister also for more power out. forget just what one it was but it made the 29 work just fine.
for some reason the truck drivers would come in and want a large final as they would call it for more out put.
it has been to long since I did that so not sure just what all I did for sure. the radio would swing up to about 25 watts on my dosey meter I used. the original final would on put out about 15 to 18 watts and the driver would think he was talking over every one else after the mod.. to me it was just a mind set for them. you could here them bragging about how much the radio was putting out with a single final.
back then I would only charge them 25.00 for labor and parts so not a lot of money at the time. the final was about 2.00 and the driver about 1.50 and a 5 cent resister and maybe a cap to get it to swing.
for some reason the truck drivers would come in and want a large final as they would call it for more out put.
it has been to long since I did that so not sure just what all I did for sure. the radio would swing up to about 25 watts on my dosey meter I used. the original final would on put out about 15 to 18 watts and the driver would think he was talking over every one else after the mod.. to me it was just a mind set for them. you could here them bragging about how much the radio was putting out with a single final.
back then I would only charge them 25.00 for labor and parts so not a lot of money at the time. the final was about 2.00 and the driver about 1.50 and a 5 cent resister and maybe a cap to get it to swing.
I did this mod with a uniden 76xl and I get backswing when my variable power is all the way up on an external meter
If it doesn't look good on the 'scope, it's not a good mod.
Absolutely correct, Leapfrog.
You can't squeeze blood out of a turnip and you won't get 50 watts pep out of 2SC1969 no matter what kind of mod you do. Period. You may see this on a cheap meter, but it is the harmonic content that you're seeing. The absolute maximum output of a 2SC1969 is 25 watts peak, so anything more is a pipe dream.
There are a lot of mods out there that look good on cheap meters, but common sense says that you can't make a 25 watt peak transistor make 50 watts, no matter what snake oil you use. Anyone saying otherwise is only fooling themselves, and trying to fool everyone else.
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