Cobra 25ltd pll part # needed

[dss56]

I have a cobra 25ltd mfg date 2013. The pll is bad I had a good one from a good 25ltd mfg date 2006 and worked.
I did get some info that a TC1906 would replace the cobra 25ltd pll well I tried 4 TC9106s and will not work it is not the replacement for the cobra 25ltd which i thought it was.

So I had a friend with a 25ltd mfg 2006 and we pulled his chip and tried in my 25ltd and worked great.
So I hope someone can tell me the correct part # for the pll replacement. Here is a picture of the chip with just cobra 25ltd on it no part #. I have tried all the schematics out there and many sites and all refer to the chip as IC3. I'm determined with your help to get this radio back on the air. Thanks for the help in advance

 

[Handy Andy]

Firstly it's TC9106 for an older Cobra 25 - Even Realistics use this PLL too... but Uniden - the Cobra "Brother" uses an SM5126
All seem to be pin compatible - so no guarantees
Cobra ID Part # as KEIC - 25LTD - IC3

That's all I got..

Only other option is the schematic...and that is to an OLD-ie....attached to this post - open at your leisure...
The graphic is for the older 9106 chip - I hope it helps you decide which route to take....

 

[loosecannon]

my opinion is that neither cobra or uniden is going to spend one red cent in re-designing one of the best selling CB radios in history.

i would buy a TC9106 and drop it right in there.
LC

 

[Handy Andy]

The later versions of the Cobra use the 25LTD "Style" chip...

So what makes me wonder then, if this chip can work better...

This is from a PC68 Manufactured in 1997 - so yes its old - but here goes...


See if comparing the "glow thru" PC traces below the chip can help line up to spots on your radio - if it does you may be able to get away with the chip being a drop in - the BCD channel selector "programming" of the pins on the PLL is the only hang-up.

 

[kopcicle]

President Herbert (old) near enough to the 25 and the only place I remember the SM5126BP being subbed for the TC9106 . In french , sorry all I have ?! Ajouter = add...

This may be the only difference between the installations and or it was used to quiet oscillations in the loop filter ? Close as I get . As far as availability I hope you write and or speak Chinese.

 

[kopcicle]

the whole manual if needed

 

[Handy Andy]

Hi @kopcicle

Pin 8 is the "toggle line" for RX/TX IF 455kC shift...runs off of the Pin 3 "shift" to TX (Pin 3 to GND - Pin 1)

Thanks to you and @loosecannon for stopping by!

 

[kopcicle]

10.240 divided by 1024 = 10khz (channel spacing)
10.240 divided by 2 = 5.12 times 3 = 15.360
Digital input to the divider is .91 Ch 1
TX oscillator is 10.695

15.360 + 10.695 + .91 = 26.965
10.695 - 10.240 = .455

where did that come from?

 

[TheRealPorkchop]

You are a scholar and a wizard.

 

[dss56]

I did try a good 9106 and did not work it made the led display work ok the bad chip made the display not work correctly. and some of the channels were not working. I took a good 25ltd mfd 2006 pll and it worked correctly.
Someone said a 9106 will work and I tried 3 of them and all 3 made the channel led work correctly but no correct channels 1-40. No transmit.

 

[TheRealPorkchop]

So you want a part number or a used PLL from the same year model 25? Let me look through the radio graveyard... I’ve been doing that a lot lately it seems.

 

[dss56]

there is no part # on pll just cobra as pictured in first post. I tried searching/google and nothing has popped up

 

[dss56]

any pll from 2006 up to 2013 from a 25ltd will work again no # even in the schematics I googled everything and zilch nothing

 

[Handy Andy]

Hmm - even a NPC5126 chip too?

 

[dss56]

Have not tried a NPC5126 ill see if I can get one on ebay and try it