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best option for blown final 148

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9Lives

Active Member
Oct 3, 2012
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I believe the final is blown bc it is output 1 watt give or take but looks good on the scope still.

What is my best option? It's a new front Mic. I have several 2030 and 520s I only have the erf 1230?m can't remember, it's the one for cobra 29s. I also have a c1307, and a few 1969 that may be blown as well
 

Test all of the NPN transistors with your DVM. Toss out all the ones that fail. If you don't know how to test an NPN or PNP transistor yet; then read up on it and watch some videos on YouTube. Testing MOSFETs is a different process; that can also be found on the net.

The best replacement for the 1969 is the Eleflow 1969 or 2312.
The best replacement for the new 4 pin front mic Cobra 148 - is the older 5 pin side mic plug 148.
 
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I would replace it with what ever final and driver is in there now. The ONLY way I would even consider a mosfet conversion is if you can no longer get the stock final or the cost outrageous.
 
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Yep, go with a bipolar transistor if you can. You can replace the C1969 with the following numbers and they will all work with retuning.

2sc1969 (and its Eleflow equivelant), 2sc1307, 2sc1817 (rebranded 2sc1307), 2sc2312 (and its Eleflow equivelant), a 2sc1945 will work, but the base and collector pins are reversed, so you have exercise caution when installing this transistor.


Robb and 9C1 Driver both have you in the right direction.


~Cheers~
 
It may not even be the final. You may have a bad driver and are getting just a little bit of power from the predriver. Use exact replacement when possible. If it is a 1969, just a heads up, stay away from copper's replacement. Its a cb20w and is worthless. It works, but no where near what a 1969 final would do.
 
Crusher said:
It may not even be the final. You may have a bad driver and are getting just a little bit of power from the predriver. Use exact replacement when possible. If it is a 1969, just a heads up, stay away from copper's replacement. Its a cb20w and is worthless. It works, but no where near what a 1969 final would do.
Click to expand...

First time I heard a bad thing about the Eleflow transistor (CB-20W).
The NTE-236 is the one to avoid, as it definitely will not perform like a OEM 2sc1969 will.
 
Robb, Workman makes a knockoff copy of the Eleflow CB-20W final, and those are junk. Copper/H&Y sells the junk Workman finals. And Crusher is right, avoid 'em like the plague. The genuine Eleflow finals are quite good, I have used them in SSB rigs with no problems.


~Cheers~
 
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I've got a few on the way from futurlec. I ordered them 2 months ago. Anyone got experience from them? The comment you made driver makes me suspicious. It's there a way I can tell which one it is? The wave form looks perfect on the scope but ssb doing 3 watts. I know this radio is junk and I will never purchase one again but it still worth fixing imo. This 1307.. it has reverse pin? Only reason is it the only one UN used.

It might be the driver, if it was the final wouldn't there be some distortion on the output? Also the volume on AM is lower than it should be.
 
The C1307 final is a direct drop-in. It might put out a watt less or so than what a C1969 would, but it will work fine with some retuning.

I'd almost suspect that the cans in the TX chain are out of alignment. I have had radios come across my bench with low power like yours, and all I've had to do was re-align the inductors (cans) in the TX chain, and all was well. This might be something to consider, before you do any changes to the final, driver and/or predriver.

~Cheers~
 
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9Lives said:
I believe the final is blown bc it is output 1 watt give or take but looks good on the scope still.

What is my best option? It's a new front Mic. I have several 2030 and 520s I only have the erf 1230?m can't remember, it's the one for cobra 29s. I also have a c1307, and a few 1969 that may be blown as well
Click to expand...
 
This is not indicate a blown final. many have said to avoid a mosfet replacement, I agree!!
the ELEFLOW TRANSISTORS are terrific I have used them on more radios than I can count They are merely an original spec. 2sc1307 that will handle more power than the original. I did radio design for path-com in the late 60's and early 70's we were buying 2sc1307 and mps8004 transistors but had to switch from these to something else so the FCC would get off our butt. with a simple re-tune the transmitter would go 12 to 20 watts on the 2300 we commonly had customers complain that after the radio would leave the factory for a receive problem the transmitter was not as "strong" I often had to explain that the transmitter was set way too high that 30 watts was not legal for CB the same unit was sold for taxi cab use and 30 watts was legal for them. they would take it to a local screwdriver and i am sure it was right back to the 30 watts it was capable.
 
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RF Parts still has the real 2SC1969s at $16.95 a piece. If the radio is a new front mic 148.........replace with a side mic 148.
 
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so do I, but in some cases I prefer a ele 20-cb I have been able to get 20 watts from them on a regular basis then you can tune into a safe area so the signal doesn't flatten and cut the peaks off
 
9Lives said:
I've got a few on the way from futurlec. I ordered them 2 months ago. Anyone got experience from them? The comment you made driver makes me suspicious. It's there a way I can tell which one it is? The wave form looks perfect on the scope but ssb doing 3 watts. I know this radio is junk and I will never purchase one again but it still worth fixing imo. This 1307.. it has reverse pin? Only reason is it the only one UN used.

It might be the driver, if it was the final wouldn't there be some distortion on the output? Also the volume on AM is lower than it should be.
Click to expand...
 
starting at the out put go backward to the predriver checking the output by tweeking the coils to see if you can increase the out put of each stage. when you find a stage that will not adjust higher, this is where you begin to look for the real problem. look for defective parts in the bias or just pull the transistors and check them. the look in the signal line for a bad mica cap. I recently had a problem very similar and it ended up a 150 pf mica cap had changed value to 10 pf. did not have enough to transfer the signal.
 

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