Image

cobra 19 dx 3 lowering the dead key

Need some help with a radio mod? Pop in and ask away.

Moderator: JR Moderator

User avatar
mustang056
Mud-Duck Sr.
Mud-Duck Sr.
Posts: 6
Joined: Tuesday, 10 November 2009, 16:15 PM
Name: TJ
Home Phone: 3864902567

cobra 19 dx 3 lowering the dead key

Post by mustang056 » Wednesday, 11 November 2009, 19:03 PM

What i did was put a 10 ohm resirtor and another diode where DM2 is on the board this droped the dead key to 1.5 watts. i used 1 watt resistors but they get vary hot do you think this it ok? i also put a 220pf cap on there(dont know what good that does)

The audio still sounds good and i held it key down for about 1 min and no smoke came out. ( Good thing too, because i dont have any smoke on hand)




User avatar
WESTGATE
Donor
Donor
Posts: 495
Joined: Thursday, 24 September 2009, 20:23 PM
Name: randall robles
Location: WESLACO, TEXAS

Re: cobra 19 dx 3 lowering the dead key

Post by WESTGATE » Wednesday, 11 November 2009, 20:49 PM

good question im looking to do the same mod to the same radio so i can run a RM KL-200, i wanna make a killer rental car setup, hope someone has some answer on the deadkey,

Randy


WESTGATE
Image

User avatar
mustang056
Mud-Duck Sr.
Mud-Duck Sr.
Posts: 6
Joined: Tuesday, 10 November 2009, 16:15 PM
Name: TJ
Home Phone: 3864902567

Re: cobra 19 dx 3 lowering the dead key

Post by mustang056 » Thursday, 12 November 2009, 7:59 AM

Yea i will get a pic up later on to show what i did. i put the 2 diodes in line for the voltage drop they have and then i added resitors in series until i got the dead key down to where i want it. now i want it lower. im thinking about a 1/2 watt dead key



User avatar
mustang056
Mud-Duck Sr.
Mud-Duck Sr.
Posts: 6
Joined: Tuesday, 10 November 2009, 16:15 PM
Name: TJ
Home Phone: 3864902567

Re: cobra 19 dx 3 lowering the dead key

Post by mustang056 » Thursday, 12 November 2009, 13:28 PM

here is a pic of it. the resitors got hot enough to shrink the shrink wrap.
Image



User avatar
WESTGATE
Donor
Donor
Posts: 495
Joined: Thursday, 24 September 2009, 20:23 PM
Name: randall robles
Location: WESLACO, TEXAS

Re: cobra 19 dx 3 lowering the dead key

Post by WESTGATE » Thursday, 12 November 2009, 15:05 PM

lol...your a trip dude... :r&r: ....did u just disconnect the wire that was solder to the SO-239 and put all the resistors and diodes inline..?seems simple enough...how does it work out for you??would one diode and just 1 certain value of resistor work??interesting and seems like an easy fix,

randy


WESTGATE
Image


User avatar
WESTGATE
Donor
Donor
Posts: 495
Joined: Thursday, 24 September 2009, 20:23 PM
Name: randall robles
Location: WESLACO, TEXAS

Re: cobra 19 dx 3 lowering the dead key

Post by WESTGATE » Thursday, 12 November 2009, 15:12 PM

ooOOoooo.....nevermind i see what u did here....my bad , lol in my head i was thinking about what i saw at first and was like......i duunnnooooo....its all good sweet man i gotta try that out, thanx for the pix


WESTGATE
Image

User avatar
Night Crawler
Wordwide & Qualified
Wordwide & Qualified
Posts: 3839
Joined: Tuesday, 15 May 2007, 8:03 AM
Location: Northern NJ
Referrals: 1

Re: cobra 19 dx 3 lowering the dead key

Post by Night Crawler » Thursday, 12 November 2009, 15:17 PM

mustang056 wrote: i used 1 watt resistors but they get vary hot do you think this it ok?
No that's not ok.
There's a reason for that if you used it where DM2 is the driver and final are pulling over one and half amps of current through that 1 watt resistor sooner it later it will fail.

A better way to do it is to replace RT12 a 10 ohm 1/2 watt resistor that's going to the collector of the driver with a higher value. Also you could put a 100uf-200uf cap across it if you want the lower dk with the swing.



User avatar
mustang056
Mud-Duck Sr.
Mud-Duck Sr.
Posts: 6
Joined: Tuesday, 10 November 2009, 16:15 PM
Name: TJ
Home Phone: 3864902567

Re: cobra 19 dx 3 lowering the dead key

Post by mustang056 » Thursday, 12 November 2009, 16:37 PM

A better way to do it is to replace RT12 a 10 ohm 1/2 watt resistor that's going to the collector of the driver with a higher value. Also you could put a 100uf-200uf cap across it if you want the lower dk with the swing.

this sounds like a good plan i was about to get a 10 watt resitor and put on there i will open her up in i min and go after the driver. thanks ill put some pics up



User avatar
WESTGATE
Donor
Donor
Posts: 495
Joined: Thursday, 24 September 2009, 20:23 PM
Name: randall robles
Location: WESLACO, TEXAS

Re: cobra 19 dx 3 lowering the dead key

Post by WESTGATE » Thursday, 12 November 2009, 16:55 PM

which direction does the negative side of the capacitor face?towards the driver??im almost sure it faces towards the rear of the radio but just wanna make sure


WESTGATE
Image

User avatar
Night Crawler
Wordwide & Qualified
Wordwide & Qualified
Posts: 3839
Joined: Tuesday, 15 May 2007, 8:03 AM
Location: Northern NJ
Referrals: 1

Re: cobra 19 dx 3 lowering the dead key

Post by Night Crawler » Thursday, 12 November 2009, 18:19 PM

mustang056 wrote: this sounds like a good plan i was about to get a 10 watt resitor and put on there i will open her up in i min and go after the driver. thanks ill put some pics up
RT12 the 10 ohm resistor is already there.
What has to be done is to remove it and replace it with a higher value. The value of the resistor will depend on the amount that the carrier is to be lowered. Experiment with different values until the carrier is set where you want it.



User avatar
Night Crawler
Wordwide & Qualified
Wordwide & Qualified
Posts: 3839
Joined: Tuesday, 15 May 2007, 8:03 AM
Location: Northern NJ
Referrals: 1

Re: cobra 19 dx 3 lowering the dead key

Post by Night Crawler » Thursday, 12 November 2009, 18:22 PM

The negative side goes to the collector of the driver.



User avatar
mustang056
Mud-Duck Sr.
Mud-Duck Sr.
Posts: 6
Joined: Tuesday, 10 November 2009, 16:15 PM
Name: TJ
Home Phone: 3864902567

Re: cobra 19 dx 3 lowering the dead key

Post by mustang056 » Thursday, 12 November 2009, 20:04 PM

all right with the help of yall i got this done. the dead key on this radio is now 1 watt and it swings up to about 2 watts. the amplifier is no longer making any splader and the tx bandwith is about 15 khz .

before i got the dead key down the tx bandwith was about 1 mhz :bom: because the amp was so over diven.

I went with adding 110 ohms in series with rt12 thanks to night crawler, and got good results.

Also note this could have been done much cleaner but there is a good amount of room in there so what ever.

a good idea might be to put a potentiometer on the back of the radio so you can change the output as needed. i did not do this because i dont have one on hand.

Image



User avatar
WESTGATE
Donor
Donor
Posts: 495
Joined: Thursday, 24 September 2009, 20:23 PM
Name: randall robles
Location: WESLACO, TEXAS

Re: cobra 19 dx 3 lowering the dead key

Post by WESTGATE » Thursday, 12 November 2009, 22:47 PM

this was a pretty sweet post here man....just in time i was looking all over where to get a low dead key and still sound good.....awesome..

randy


WESTGATE
Image

User avatar
mustang056
Mud-Duck Sr.
Mud-Duck Sr.
Posts: 6
Joined: Tuesday, 10 November 2009, 16:15 PM
Name: TJ
Home Phone: 3864902567

Re: cobra 19 dx 3 lowering the dead key

Post by mustang056 » Friday, 13 November 2009, 6:20 AM

also note dm2 has not been removed i just moved it to the other side of the board. the red wire just carrys the 13.8 volts to the resistor at rt 12



User avatar
Sporty Mike
Wordwide & Qualified
Wordwide & Qualified
Posts: 1635
Joined: Friday, 13 November 2009, 17:02 PM
Radio: Alot of 'em!!
Antenna: S.S. 102 / Maco V5/8
Name: Michael
Home Phone: 205-683-9333
Cell Phone: 205-400-5810
Location: Trussville, Alabama
Referrals: 1

Re: cobra 19 dx 3 lowering the dead key

Post by Sporty Mike » Monday, 07 December 2009, 18:58 PM

Far out man :r&r:


Amazed,

Mike


Redbeard 759 , your non profit Prophet from the 'Bam!!!


Image

User avatar
Mr707
Mud-Duck Jr.
Mud-Duck Jr.
Posts: 4
Joined: Friday, 10 February 2017, 5:48 AM
Name: Big Red

Re: cobra 19 dx 3 lowering the dead key

Post by Mr707 » Saturday, 11 February 2017, 3:19 AM

LOL im was just doing this the other morning this pic was on google and now im on the cb website as a member LOL yes its working but I had no one watt just a lot of 1/4 watt resistors at different values (Radio Shack) so put 4 100ohm together and looks a little different but LOL she's talking LOL also my first post on this website thanks guys ohh yea sounds good also added a fan to the little radio LOL LOL and thermal compound to my wrapped together resistors cool old radio was sitting for couple years until i thought of this and I guess great minds think alike




Post Reply Previous topicNext topic