148gtl pluged in backwards

sandy · Post by **sandy** » Monday 28th Jan 2008, 4:33

I pluged my 148 in backwards, now no receive or trans. lights com on channel led lights work and when you key the mic. the red light indicator doesn't light I checked ic 4 all volts good except last pin trans side but won't key so I don't count that I can smell some thing burned but can't see any thing I have volts to the final but won't key up so can't check any thing else? dose any body have any idea?? thanks.

Rick · Post by **Rick** » Monday 28th Jan 2008, 5:15

Which one of the 148 are you talking about?

The only way we can help you is for you to help us.
So please read the info in the link below, or you post will be ignored.
www.radiomods.co.nz/forum/viewtopic.php?t=312

sandy · Post by **sandy** » Monday 28th Jan 2008, 8:32

this is a 148 gtl made in 1997 in malaysia board only # i can find is
ept01481 z and pll ? rci8719-a if that will help. thanks

Rick · Post by **Rick** » Monday 28th Jan 2008, 9:40

What is the voltage at the Emitter and Collector of TR40 in TX and TR44 in RX also, what are the voltage at Pins 1 and 3 of IC4 and the voltage at each side of D4?

It is most likely you will need a new AF amp IC6 (KIA7217).
You will most likely find diode D55 by the power socket has gone south and maybe D56 also.

sandy · Post by **sandy** » Monday 28th Jan 2008, 12:19

rick can't find tr40 or tr41 or d4 ck d55 d56 ok yesterday the channel light came on and when I ck ic4 volts were good now I re checked it and they are
pin 1 1.185
2 13.5
3 .606
4 0 all wrong according to chart
5 13.5
6 .078
7 .078
8 .10

but I haven't done any thing to it all I did was unplug it and leave it alone?

Rick · Post by **Rick** » Monday 28th Jan 2008, 12:43

The diagram I have for your radio is the wrong one. Do you have a copy of the diagram?
Is IC4 a MB3756?

sandy · Post by **sandy** » Monday 28th Jan 2008, 12:53

rick I think that is the # the diagram I have shows tr40, tr41 also but it isn't there??? I have never messed with these before most of my stuff is 29s but I'am pretty good at finding parts on the board but can't find them..

Rick · Post by **Rick** » Tuesday 29th Jan 2008, 0:42

I did ask is IC4 an MB3756, if it is so then replace it and the AF Amp IC6.

See my diagram it may help you see how the MB3756 voltage reg works in the Cobra 148 GTL

http://www.cbtricks.com/radios/cobra/14 ... redraw.pdf

sandy · Post by **sandy** » Tuesday 29th Jan 2008, 3:02

Thanks I'am going to oder them first thing this morning i'll let you know .
again thanks!!!

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