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Radio Make and Model:MK2 Cobra 18GTL DX
PCB Number: PB 010 AB
PLL Number: MC145106p
Test gear available: Loads
Symptoms: TXing all the time

What is working:TX

What has been tried: see below

Did it suddenly happen ?: Yes, when it was thrown against the wall.
Anything else that may be of help.


I have a Cobra 148GTL DX MK2 that goes into TX as soon as it's switched on, even without the mike.
I've fitted loads of new parts (listed below) but it's still the same.
What I have done is to de solder pin 5 of IC4 the OP- AMP and I get RX, I also had to de-solder the CW wire from the mode switch to stop it giving out a tone when switched onto CW, I've put 6 different IC's in at IC4 but it's still not cured the fault that happens in all modes.
Things that have been changed are,
TR 32, 33,34, 35, 36, 37, 38, 39, 40, 41, 42, 54, 55.
D76, 77, 78, 79, 80, 81, 82, 83, 86, 87. 88, 89, 90, 91, 92, 95, 105.
C138, 144, 146, 148, 149, 150, 172, 173, 174, 179, 227, 228,
I've never come across this fault before without fixing it.

Help Please.
Dave.

Problem resolved.
It was the CW socket that had a single strand of wire from the speakers 0v lead that was causing the problem. I decided to remove the socket just to make sure it wasn't shorted as I was convinced it had to be that after checking everything else, even though I'd checked it for a short previously,