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BK Cobra 98 schematic

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db-shortwave
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Radio: BK Cobra 98 W.I.P.
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Name: Aaron

BK Cobra 98 schematic

Post by db-shortwave » Monday, 27 January 2014, 8:46 AM

About 12 or 13 years ago I purchased a Cobra 98 and did some poking and prodding to get some signs of life out of this radio and I did with the help of a friend. I ran this rig for maybe 20 mins knowing it had issues (stone me later for doing this) and it needed some extra TLC but I was happy that everything worked inside an I shelved the unit for a "rainy day project". More recently the rainy days are coming faster and staying longer an I need to keep my hands busy. The repair bug has bit me and I want to try my hands at a transmitter and expand my skills a little.

I am on a quest for mercy and salvation in hopes of a set of schematics and alignment data for this radio. I would like to bring this rig back to its original specs after the lightning strike it took many moons ago. ANY help would be grateful.

Here is a list of issues "remembered" and recently discovered.

resistor's have drifted
electrostatics are dry (self explanitory)
SWR meter pot wrong value and needs to be adjusted.

Some things had been repaired, there was a piece of substrate that was on the antenna output had been blown apart. Assuming was from the lightning. and some resistors had been "guessed" at to bring it to life and to make sure everything was 'ok' since I didn't have a tube checker at the time and to see if it received. Hence the request for info. I have pictures of this radio on imgur.
I'm not looking to sell this radio I want to use it I haven't been on a CB in a good 15 years.




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Bombero
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Re: BK Cobra 98 schematic

Post by Bombero » Monday, 27 January 2014, 10:18 AM

Hey..

CBTricks.com is usually the place to find schematics and other good info.

Here is info on your Cobra 98 : http://www.cbtricks.com/radios/cobra/98gtl/index.htm" onclick="window.open(this.href);return false;

Bombero


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MDYoungblood
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Re: BK Cobra 98 schematic

Post by MDYoungblood » Monday, 27 January 2014, 17:01 PM

Hello db-shortwave,
Welcome to the forum. Boy, a B&K Cobra 98 is really hard to find, I remember the Cam 88 but never had one. Your best bet is to track down a copy of the Sams Photofact #CB-23. It has the info you need and would be well worth the price if you plan to sell the radio at a later date.

3's

Greg


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db-shortwave
NEW DUCK
NEW DUCK
Posts: 2
Joined: Monday, 27 January 2014, 7:09 AM
Radio: BK Cobra 98 W.I.P.
Antenna: Wilson 2000
Name: Aaron

Re: BK Cobra 98 schematic

Post by db-shortwave » Tuesday, 28 January 2014, 4:57 AM

Wow thanks you guys!
The other day I dove into the power supply section an replaced the main filter cap and replaced the one 1k 2watt resistor. Cleared the hum right out and changed a few tubes out from the collection of spares I've got. I also changed out the one pot for the swr meter since it was locked up tighter than a drum. Wouldn't move. Sprayed the switches and pots with contact cleaner and i was able to hear skip with a 5 foot piece of wire on channel 6 with a room full of various noise producing electronics. Its what I was aiming to do. As for transmit that will have to wait till I build a dummy load and scare up a mobile radio to see if I get a hum on transmit with the dummy. Once I get this thing cleaned up its more than likely going to sit on my Sony stereo next to the computer. :lol:



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MDYoungblood
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Re: BK Cobra 98 schematic

Post by MDYoungblood » Tuesday, 28 January 2014, 9:38 AM

Making a dummyload is easy , look up "Saltwater Dummyload", all you need is a jar with a lid, a couple pieces of copper wire, a connector or coax, water, and salt (about an 1/16th to an 1/8th of a teaspoon depending on the jar size). Use a multimeter to adjust the mixture to 50 ohms. I like that you are doing the dummyload for testing and I do the same thing with an old 23 channel radio with a homemade attenuator/dummyload and headphones to hear how the radio sounds. It is a good start to making a workbench.

3's

Greg


"321, the Middle of Maryland"

23 AM "WORLD WIDE" 38 LSB

Strong Supporter of America's Original Homeland Security Act
The Second Amendment



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