Kraco kcb4007 (what I learned before I let the smoke out)

[sunbulls]

It makes me wonder what dealer sold those Jeepers that radio, either ignorant or unscrupulous. Take your pick. I love refurbishing or improving older radios that few people want, it’s kinda my thang, but I draw the line when even SAM’S catapulted over that radio like a plague infected rat. It’s one of the very few radios that I toss into the parts bin before cracking open the covers. Once was enough. The value for me mainly consists of the LED display and the Pll.

 

[Shadetree Mechanic]

I've been messing with different cap values in the output and driver stage. The stock driver transistor which is a 2314 is not heat sinked at all stock. It's in the whole backwards but they made it real convenient to drop an irf510 in there and it actually sounds pretty good driving a 520. I'm doing a recap later on tonight of all the electrolytics, which is honestly not that many, and I will see where I am at from there. I suspect I'm going to poke around the audio section and Mic preamp and maybe change out the AMC limiter release cap to something faster

The AMC release cap really opens up a Cobra 29. I suspect the Kraco has a modulation transformer? You should post some pictures so we can see what you are having fun with.

 

[Handy Andy]

The AMC release cap really opens up a Cobra 29. I suspect the Kraco has a modulation transformer? You should post some pictures so we can see what you are having fun with.

+1

Hint it does, but the parts driving it - OMG! UGH! - remember the TDA 2003? I think this one has it - much like the Mayday. I had...

 

[Uncle Ronnie 336]

It does have a TDA 2003. Is that schematic the same radio in question? I know there was a resistor on the driver transistor which went from base to collector like it was biased in class A or something. I know I don't have this thing fully tuned out yet with the irf510 driver pushing a irf520 but even so I already got higher peaks and the audio on transmit is much louder than it was.

 

[Uncle Ronnie 336]

Also to get close to where I'm at with the mos RF section, I basically pulled all of the air wound coils and replaced them with tuning slugs out of some parts pigs. I put the smoke back in and we are back in business as far as getting this thing maximized. I have another question about the modulator, is the TDA 2030 a drop-in replacement?

 

[Handy Andy]

Need the "clipping Drive" diodes to help clamp the spikes so they don't blow the output Change C36 Electrolytic to a 150ohm 1/2W resistor, install a 4.7uF (475) Electrolytic + towards Pin 2) IN SERIES to/with R40 - R40 to a 47ohm and pull R72 - it can work, just this device isn't for the Cobra 25/29 using the 2005 chip - feedback and biasing is different for those.

I'm referring to my schematic for that 2030 conversion - the output "floats" due to internal regulation - so the output has a DC bias, which returns to the Pin 2 of the IC, don't try to shunt it (R72) for it will drive the thing to clip because of the DC offset bias is pulled low, it will try to push it back up - ruining your effort.

 

[Uncle Ronnie 336]

Very good thank you for the info. I will let you guys know when I order that part what the translation of that circuit comes out to on this radio.

 

[Uncle Ronnie 336]

Also if anyone is watching this has this model radio please send it to Handy Andy (and pay the guy if you get the radio back screaming)

 

[Uncle Ronnie 336]

It makes me wonder what dealer sold those Jeepers that radio, either ignorant or unscrupulous. Take your pick. I love refurbishing or improving older radios that few people want, it’s kinda my thang, but I draw the line when even SAM’S catapulted over that radio like a plague infected rat. It’s one of the very few radios that I toss into the parts bin before cracking open the covers. Once was enough. The value for me mainly consists of the LED display and the Pll.

Locals here just tend to find a cheap radio at a tag sale or on eBay not always knowing what they are buying. The 4x4 Bros tend to prefer smaller sized radios.

 

[9C1Driver]

There are some Jeep and 4x4 camping locals that had good luck adding a KL60 or KL203 to the smaller cb radio's. The Uniden 980 and 122xl were the choice for the few that also wanted SSB.

 

[Uncle Ronnie 336]

Yeah unfortunately the bearcat 980 is roughly the size of a Cobra 29. I have one in my truck.

 

[Uncle Ronnie 336]

:: UPDATE:: I*R 520 FET has been dropped in and now I have about 3.25w carrier, and 25w peak! This little junk box is SCREAMIN with an 80s realistic microphone. So I'm thinking I will be making the checklist for this model radio. A 4pin Cobra wired microphone connector is getting slapped on and I'm thinking I might order a ranger SRA 198 for a microphone. I basically rebuilt the whole driver and final stage.

 

[Handy Andy]

This little junk box is SCREAMIN with an 80s realistic microphone.

AWESOME!

Glad you kept at it!

 

[Uncle Ronnie 336]

The vishays were alright, but the I*R def gave me a couple more peak whiskeys

 

[Uncle Ronnie 336]

Stock vs. hot.