Cobra 142gtl transmit issue

[Stovepipe]

Hello all, I have a transmit/power out put problem. I was talking on the 142 yesterday, barefoot about 10 watts. Out of the blue I lost my carrier and modulation.

If I turn the radio off and turn it back on and key up right away the meter will swing up to about 5 watts and within 20-30 seconds the meter slowly drops down to 0. During the 20-30 second time period I am able to transmit and I'm told it sounds like it normally does, but drops down to 0 output. No carrier, no modulation. The person I am talking to can hear the audio gradually get worse until I drop totally. After everything drops out and I turn the radio on and off I have another 20-30 seconds to talk before I have to shut it down again.

8 out of 10 times that I turn the radio off and on again the radio will not even key up (no transmit light) and sometimes when I key the mic the transmit and receive light flash on and off.

I should mention that I was using a studio mic and a mixer wired to the audio wire in a stock mic to to key up. I was having no issues.


I'm not even able to check SWR's,

Would this be the finals? Caps?

Very odd how it's fine for 20-30 seconds....

The receive has also cut out twice, without me touching anything but if I turn the radio off and on again the receive is back????

Anybody have a clue? Help....


-Stovepipe

 

[Robb]

Check the radio in PA mode and see if there is audio out - first.

If not; then it could be the power supply, the voltage regulator, or cold solder joints.
Not enough info.

Start simple. You are going to need a DVM and check voltages in/out of the voltage regulator when the failure occurs and find out if it is not getting enough voltage before it gets to the regulator. If not; then it is the power supply. If you see steady voltage coming in the voltage regulator after the radio drops out again; then check the output voltage of the voltage regulator. If not seeing 8v; then the regulator may be at fault. Or there is a short elsewhere and may need to be sent to a shop; an old electrolytic cap may have shorted somewhere - but not necessarily.

First blush guess would be the internal power supply. Try running an external 13v power supply thru the DC plug in the back. If that problem stops; then the power supply needs work.

 

[Stovepipe]

I tried running DC and got the same results. I believe repairing/restoring the 142 is beyond the scope of my ability so I am probably just sell for what I can get out of it and put it towards a new radio. It's been many moons since I bought a NEW radio and I think it's about that time. Till then talking on a borrowed Cobra 90LTD, kind of a neat looking little thing.

Thanks for your input....

-Stovepipe

 

[M0GVZ]

Have you checked the power supply?

 

[Stovepipe]

Have you checked the power supply?[/QUOTE

No, only tried running DC. I'll put a meter on it when I get home from work.

-Stovepipe