cobra 148 unlock PLL

[Handy Andy]

Hmm. I remember a conversation or two about a pin on that PLL that may need to be puled hi or low - because if left floating - doesn't always "toggle" the right channels.

Maybe this link?
https://www.worldwidedx.com/threads/l21-frequency-mod-for-mb8719.234452/

Talks about Pin 10 - acts kinda like a carry function for frequencies.

Only other things I can think of to check is,

Does your radio have a working 10.240 Xtal in it?

 

[loosecannon]

well Robalo, i know i haven't been much help on this problem, but i wonder if your tripler coil is doing its thing or not.
i don't have the time to read through the whole thread, so please disregard if you've already exhausted this possibility.
im talking about L21.

do you have 33mhz signals on the emitter of TR20?
if not, can you try fiddling with L21 while you have the freq counter connected to TR20 emitter?
maybe, just maybe, you might get this thing to start oscillating.
totally guessing here...
LC

 

[Robalo]

Ok LC i let you know

 

[SIX-SHOOTER]

no radio is not RX and no TX. I want to fix it as factory.

I have a Cobra 148 GTL (Philippines) that I am pretty sure is unlocked since it transmits on the same frequency no matter what channel it is on.It's not even a CB Channel that it does this on? I have a Cobra 29 doing the same thing.

SIX-SHOOTER

 

[Robalo]

six-shooter on cobra 29 check C112

 

[Robalo]

well LC tr20 (2sc1675) C and B read 324740 46 MHZ and E do not read nothing and l21 been replace again hmm i am close to the rabbit? tr29 C READS 324850 11 MHZ

 

[Handy Andy]

Did you replace TR20?

IF not already done so, pull the part - leave everything else in place, power it back up and look for DC voltages on the holes for TR20 - gotta' check BIAS to make sure you don't blow TR20 again. You lost Emitter - unless you have a blown Coil feeding it.

8 Volts on collector - 4 volts on Base and NONE on emitter (DC).

Ok, TR20 IN PLACE? Now remeasure...Collector? Should be about 8 volts, Base? About 4 - Emitter? About 3.3~4V

You may have lost L21 or you have a short somewhere in the can itself.

 

[Robalo]

Remover TR20 b 4:14v c 8:33v e 0.0v now tr20 back b 4:1v c 8:31v e 3:49v
pull L21 LOOK

 

[Robalo]

 

[Robalo]

ALSO REPLACED TR27,TR22,R133,R132,C110,D61,C99,R116 WE see tomorrow

 

[Robalo]

Happy thanksgiving to all here on the forum. Thank you for helping on my repairs.

 

[Low_Boy]

Hoping you get this going.

 

[Robalo]

I been busy with repairing my cars blown head gasket, The funny thing is some of the parts are ID'd with 148.

 

[Robalo]

 

[Low_Boy]

That sure is a long motor. Shure is not a small block chevy.