Pll chip cobra 29

[Heranney76]

Has anyone seen a 24pin pll chip in a cobra 29 nw ltd 2015 model. I was going to do the pin 14 pll to + c12 mod but didn't know how that would work out with 24pin pll
The older ones just have 22pin or ones I've seen anyway

 

[NZ8N]

Even the new 29 LX-LE radios have the 22 pin uPD2816 or their rebranded Cobra 29LTD chip in them in the schematic.
Pin 14 of the PLL is the Reference Oscillator Buffered output (10.240MHz), and hooking it somehow to C12, a 4.7uF electrolytic capacitor which is part of the RX +8v and near the RF Gain circuit, I have never heard of this mod.
Maybe the wrong capacitor number?

 

[sonoma]

I do not know what this mod is either. what does it do?

 

[LeapFrog]

I found this on Google;

Cobra 29 LTD:

Receive Boost: Locate pin 14 of the PLL chip, and the Positive (+) side of C-12. Install a 22k-220k ohm resistor between these two points. The smaller the value, the more the receive is boosted. Use CARE when soldering to the PLL chip! If desired, this mod may be wired through a switch.
Try this,it is all I could find.

Mike

And apparently the new and old PLL function the same? (early 2000's to 2015?)
http://downloads.cobra.com/CB/TSB/TSB10085.pdf
I don't know if the datasheets are easily found.

Edit: I also found this but I don't know if it is very relevant to what you're doing..

~All The Best~

 

[NZ8N]

According to that TSB , the FS pin (Pin 20) is now grounded instead of left floating if you use a new 29LTD chip in place of the older uPD2816. Maybe they switched the internals to use 5kc steps in the newer chip?
Along with the other small part changes to the VCO.

Edit - Pin 20 is grounded in the older 29LTD with the uPD2816.

Maybe the part changes are needed because the uPD2816 had a more sensitive F-IN pin than the new 29LTD chip?

 

[Heranney76]

It boosts recieve on distant station but you have to be careful as a local will overload you. You install a 22k-220k resistor inline with it. The lower the value the more it is boosted. As I said this pll has 12pins on each side only says cobra 29 series on it

I like the mod. It doesn't boost noise much but boosts audio quite a bit

 

[Heranney76]

Looks like this. Neither of my other radios have one like it

 

[Heranney76]

So based on that tsb it would attach to pin 16 but without knowing for sure makes me Leary although this ic would work in older radio what about a new one that has came factory with it?
Guess I would need to check with multi meter see which one was floating as said earlier

 

[Heranney76]

Upon checking with multimeter pin 16 has the same voltage readings as my 22 pin chip so one would assume it would be the same guess nothing left to do but try it out see I'll keep you posted. Thanks for the help guys

 

[Crossbow]

Here ya go.

 

[LeapFrog]

I found this on Google;


http://downloads.cobra.com/CB/TSB/TSB10085.pdf


~All The Best~

I guess the link to that document wasn't easy enough to find in my original post..

 

[Heranney76]

I seen the article but it is talking about retro fitting the new 24 pin into a older 22 pin circuit. I did check and voltages are the same on pin 16 which would be old pin 14 so might try it this weekend.