Cobra Realtree CB no power

[nosaj]

I've got a Cobra 29 LX Realtree model CB no lights on display.I followed the DC from Power supply to Vol pot, it appears there is 14v on every leg of the Pot. That doesn't seem like a good thing . I have a schematic but not sure where to go next.
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Thanks,
Jason

[51]

need a little more info on the symptoms. so the radio does turn on just no display or lights? (has rx/tx etc), or does it just not turn on at all?
if not at all, does it blow the power cord fuse when you turn it on?

[nosaj]

Does not turn on at all. no lights and fuse is good .
jason

[MDYoungblood]

Does not turn on at all. no lights and fuse is good .
jason

Did you try another fuse? If yes the next step is to check D10, that is the protective diode that blows if the radio is ever hooked up backwards.

3's

Greg

[nosaj]

No but the same plug works on my test Cobra 29.

Thanks,
Jason

[51]

Did you try another fuse? If yes the next step is to check D10, that is the protective diode that blows if the radio is ever hooked up backwards.

3's

Greg

the only problem with that theory is if the reverse polarity diode fails, it is usually a dead short thus blowing the power line fuse when power is applied to the radio. it is possible for the diode to go leaky but highly unlikely. i do agree on the the fuse part, use a multimeter to check the fuse and power cord for continuity. if thats all good next step is to signal trace the dc input voltage from the source thru the radios circuit to find out where it stops. also op said the power on/off pot had some dc voltage across all of the contacts, check the pot for problems with the meter, and then jumper the pot to see if normal operation is restored. let us know results

[MDYoungblood]

Did you try another fuse? If yes the next step is to check D10, that is the protective diode that blows if the radio is ever hooked up backwards.

3's

Greg

the only problem with that theory is if the reverse polarity diode fails, it is usually a dead short thus blowing the power line fuse when power is applied to the radio. it is possible for the diode to go leaky but highly unlikely. i do agree on the the fuse part, use a multimeter to check the fuse and power cord for continuity. if thats all good next step is to signal trace the dc input voltage from the source thru the radios circuit to find out where it stops. also op said the power on/off pot had some dc voltage across all of the contacts, check the pot for problems with the meter, and then jumper the pot to see if normal operation is restored. let us know results

Yes your right, need to read twice. This radio has 2 separate power sources to the switch, one turns the radio on/off the other is on all the time for the logic board, clock, and memory. With that said, next check should be IC-5 most likely that is bad.

3's

Greg

[nosaj]

I must be blind.. Looking at the schematic I posted I only See IC's 2,3,4.
Is there another schematic that lists ic numbers? I was going to pull the datasheet to determine which pins to test for voltage(power to IC), etc except I can't seem to find IC5 on the schematic I have.
Thanks,
Jason
Going to verify plug , D10 , and where power stops

[sonoma]

see if this tech bulletin will help you to trouble shoot the display not coming on. this is a common problem with some of the LX radios.

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[nosaj]

Ok when I flipped it over there is a diode soldered on the back side but right next to it a blown trace. Repaired it and my power supply is loaded down.
Start at power there is a choke at the top where the wire loops through maybe 1v there. so I pulled choke and looking at wire characteristics of burnt copper. It looks to me I can just replace the wire running through the choke. I have a LCR where I can trim the wire to make it what is needed.
Maybe it's not a choke but a ferrite core [Please login or register to view this link]
I know the European one should differ some in later stages but this one gives a layout of the PCB which helps me if it won't be a problem to use it.
i think it is l18 that I pulled listed as 752 WF What Value is that?

Does someone have a better schematic or service manual for me?
nosaj

[nosaj]

Ok hold the presses on the PCB is printed
29LBT
KEPC-1141-K1
2012 JUN 15
Gonna try and find the schematic for that.
And it appears my Google Fu isn't working well or I can't find the right schematic. The face place on this radio looks just like the one in the TSB that was posted.
Any help much appreciated



On the other hand the coil I was referring to on the PCB is labeled L201 it was burnt replaced it and power supply drags down like theres a short.
I pulled T2 and it is measuring .3 ohms

Thanks,
Jason

[nosaj]

Is there a schematic that shows the values of the components?
What would burn up, l201, T2 and blow a trace on the PCB?

Thanks,
Jason