The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

I HAVE A COBRA 29 LTD CLASSIC I WAS DOING A MOD ON.. REMOVED R123 (1 Ohm AND REPLACED WITH A JUMPER .AND Replace stock final with a 2SC1969 transistor.AFTER I DID ALL WHIS THE RADIO STILL WORKED.I Change R58 (10 Ohm) to a 2.7 Ohm AND THE RADIO QUITE WORKING.I UNDID IT AND THE RADIO STILL DIDNT TRANSMIT .I CHANGED MICS AND STILL NOTHING.ANY IDEAS?

hello,and welcome to the forum......well first of all you should never jumper out anything..i know alot of these mods tell you to jump out anti spiking diode and resistor that regulates voltage to the driver final..but these are in the circuit for a reason.and jumpering these out your only asking for trouble..so probably you have blown the driver final..

Do you have a way to test a transistor for a blown junction from base to emitter?

Time to check the driver and final both. That's what I would anticipate. That one of the two will show an open circuit from B to E.

73

i do have a way to test them but i wouldnt no what im looking for

I can't escape the suspicion that some step in your procedure went wrong, and clobbered something.

It's pretty easy to unintentionally create a solder "bridge". If the solder glob from one foil pad spills over onto an adjacent one, this can cause unpredictable failures.

Just to start, I'd check to see that you have 12 Volts DC or more on the collector (metal tab surface) of the final transistor while the mike is keyed.

If not, there is trouble upstream from the final and driver. You didn't smell anything that could have been a burned resistor or diode, did you?

73

i did nt smell any thing or here any thing pop i took it to a c.b. shop and thay said i blew the new final and driver.but every thing was working until .I Change R58 (10 Ohm) to a 2.7 Ohm . the radio still has recieve just no transmit.wouls i sheck the final with a watt meter?

what kind of driver should i use in the radio

the driver is a 2sc 1957,,also you can use a 2sc 2314.

now i want to install a super swing kit/modulation what can i ecpect every body already says my radio is loud. the mod is susposed to drop my dead key to adout 1/2 a wat and swing the rest .is ther e any truth and will it help me get out better

If you're going to run an amplifier, you will need to reduce the radio's carrier (dead-key) power level.

Cranked for all it's worth, the radio will dead key between 5 and 6 Watts. Too much for most ammplifiers.

But if you'll run it barefoot, by itself, this is TOTALLY WASTED EFFORT!

Yep. Won't increase your range by so much as ten feet, installed in a barefoot radio.

The only rational reason to install one of those is to run the radio with an amplifier.

73

ok another question is it tru you can make it where you input 16 wats in your radio or wan i go inside of my power supply and turn it up it is a pyramid 10 amp

ok another question is it tru you can make it where you input 16 wats in your radio or wan i go inside of my power supply and turn it up it is a pyramid 10 amp

i ment 16 volts or amps not to sure what to call it