cobra 29 ltd classic - stumped again!

[badfish]

Ok, so I got this radio (dead) and changed the final to a c2166. I also changed C71 to a 33uf 25v. electrolytic capicitor. I tried to adjust L17, L20, L21, L16, and L14 for max RF output, but there is no slug inside L16....it's just hollow. Looks like the stock driver is a c2314. Could this driver be weak? Is this driver junk to begin with? Should I change that to something different? No matter how I try to adjust it, it wont go past 5 watts of output. If it helps any, Mfg. date is 04' on this radio.

Forgive me, I am somewhat new to tinkering with radios. And a big thanks in advance for any help.

 

[loosecannon]

L16 never has a slug in it.
well, not on any of the 29LTD's ive had.
ive tried adding one, and it just made the output lower.
best to leave it hollow.

if you are getting 5 watts of power, your driver and final are fine.

my guess is the problem is your choice of final transistor.
the 2SC2166 is used as a driver in most of the radios you find it in.
i think there were a couple of AM only radios that used it as a final, but they would not do more than 4 or 5 watts either.

changing the final to a 2SC2078, which is the stock final in that radio should give you 6 watts or so on the deadkey and about 20-25 watts of PEP swing after a good tune up.

you could also change the final to an IRF520 or ERF2030 mosfet.
the instructions are on cbtricks.com and the kits can be found all over ebay.

what kind of meter are you using to measure the output?
does it have an AVG/PEAK switch?
is 5 watts the deadkey or the max modulated wattage?
LC

 

[badfish]

It does 5 watts, swings close to 6. I am using an old Motorola swr/power meter that seems to give accurate readings. Its only settings are 10w/100w and swr. Its probably from the 70's and has seen its use....but it does its job.

I guess I'll search for a sc2078 final. Should I leave the c2314 driver or upgrade that as well?

 

[longhaireddwb]

Sounds to me that your reading AVG. so thats about what your going to get. If you were reading PEP then it would be reading more. I've done the ERF2030 mod before and it gets you more for sure if your wanting more. Get some audio checks and see what you got right now.

 

[Dodgem250]

I'm with LooseCannon on this one. You can't use a 2sc2166 for a final in the Cobra 29, nor can you use it as a driver. You need to either use the stock originals or in most cases I go to the MosFet upgrades if I'm replacing finals / drivers. If you need the parts give me a shout, I have many here of all.

 

[loosecannon]

the 2314 is the best driver to use with that radio.

make sure that when you are aligning the TX section that you are tuning the coils for maximum MODULATED wattage.

if you just turn the coils for max deadkey, you will have no room for your modulation and can end up with downward modulation.

key the mic, say "ahhh" into the mic while you tune the coil for max reading on your wattmeter.
best to do this on channel 20 to keep the power balanced across the band.
LC

 

[Grey Coyote]

The 2166 is usually used for SSB power, like in the Grant XL and the Cobra 148 GTL