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Cobra 29 High Power mod with 2sc1969 transistor

Cobra 89XLR MOD 2sc1969 and 2166 Installation.

HELLO. I WOULD LIKE TO SEE THE PROCEEDURE FOR INSTALLING 1969 AND 2166 IN COBRA 89XLR AND WHAT COMPONENTS TO CHANGE TO GET THE BEST PERFORMANCE. THANK'S IN ADVANCE SCOTT.
 
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Wow old post, sorry for bringing' it up again. Few questions.... just like the post above. CB20w and the eleflow versions. How do you ID correctly. There is a shop called Abel near here that has them.
Those monolythics are hard to find,,,, is there a good online source?

I've read that just upgrading electrolytic caps helps sound quality and stability . Also using high quality components with tighter tolerances.
 
What is the name of the tuning coil?

Step 4 mentions a tuning coil to remove a turn from. Which coil is this ? If you can tell me which one or how to find it then I would try this mod and post it on youtube. Also I have heard of buying a different slug and inserting it for the same result? anyone know if this works?
 
they are referring to L14. dont bother with the different tuning slug, removing a turn is the way to do it.

LC
 
Want a treal easy super-modulation kit to turn it into a Modulator when you move the switch?
1.) Remove JP36 and clean out the holes.
2.) Install a 220-1000uf electrolytic cap(16-25VDC) with negative towards the final. leave the leads long.
3.) Attach jumpers to leads, starting with 60 ohms attach resistor to other end of leads and turn on and key into wattmeter and dummy load. Keep watching and dropping resistance until you get 4 watts deadkey with max swing.
4.) Adjust VR4 for 2.5 watts and turn off radio.
5.) Shorten leads and solder resistor across them.
6.) Install SPST switch in radio and run lines to both sides of resistor. This gibve you a choice between a 2.5watt dead key with monstrous audio to drive a box or about 8 watts or so deadkey with about 20 watts of swing in conjunction with the supertune.

All for educational purposes only.
 
Moleculo said:
I was asked by a few people how to do this mod, so I figured I'd just post it up.

Please don't copy and paste this mod to other sites/forums, but feel free to link to it.

Also applies to:
Uniden 78
Cobra 25 & Uniden 76 mod is similar, although you'll need to cross reference against the schematic.

1: change the final to a 2sc1969
2: change the driver to a 2sc2314.
3: change the electrolytic capacitor by the audio IC (C42, 1000uf) to a
3300uf, 16v.
4: Take a turn off the output tuning coil (see tuning coil note below)
5: Remove the AMC potentionmeter (VR4), and put a 1K resistor in it's place.
(only two connections are used on this pot, use those two connections
for the resistor)
6: add a 1K in series with D11.
7: Change R48 to a 33K ohm resistor.
8: Change R55 to a 10K 1 watt resistor.
9: change C37, and C68 to a .2 monolythic (this changes the A.F.
response on TX)
10: Now align the radio, start with the output coil, the the predriver
stage for peak output.
11: Tuning notes: Tune L17 for max with audio. Then, tune L23 for max output with audio, this will upset the radio's frequency. So, after L23 is set, adjust L24 to put the radio back on frequency.

Tuning coil note: If the radio says "made in China" on the back, you must remove 1 turn from the output tuning coil with the slug in it. If it doesn't then you may or may not have to. Count the turns, if it has 4, leave it alone, if it has 5, it's too many and won't tune, remove a turn. You may have to add a 68pf capacitor from the left terminal of the coil to ground, with the solder side of the board up. This method produces better results than just removing the tuning slug.

This mod will consistently produce output between 10-12 watts AVG and 45-50 watts peak. If I can find my video clips of Bird 43P power meter and spec analyzer I took after doing this mod, I'll follow up with those.
Click to expand...

I notice you recommend a 2SC2314 over the OEM's normally pairing a 2SC2166 with the 2SC1969 in SSB radio's. Is this just a matter of preference or is it related to gain at operating bias and voltage? Is it just that it performs better with the other electrical properties of this chassis? When I looked at the Sanyo data sheet for it they did not give the gain at the bias and voltage combo we normally see in a CB. The graphs did not do much good either too blury from years of being copied or scaned. LOL If I remember right the gain was in the 60 at 120ma, 100 at 200ma and 160 at 320ma range 2SC2314 and the gain for the 2SC2166 has gain number's about 1/2 of the 2SC2314 but seems to produce it's gain with less bias current and more total watts out but can not handle as much input bias current. I have a Uniden PC122 clone that someone did this too and was wondering why they chose those parts. Thanks for your time! I had to turn down they had it adjusted so that it was swinging to 26 watt's I turned it down to 15 did not want the thing to destroy the transformer.
 

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