View Full Version : Kenwood TM-742 Wont Power Up Correctly

08-26-2011, 06:15 PM
I am at whits end with my radio. I love it but it's becoming more difficult to power up.

Problem is it will only turn on when I ramp the voltage up from about 4 volts to 13.8 volts...and then it will only turn on sometimes and when it does its in the demo mode. I then need to reset the radio to get into normal mode. If I try just using 13.8 volts then the power button does abolutely nothing. Only issues other than the power up problem is that the backlight lamps have long been burned out. Could this be related? Where would I even get these lamps from?



09-13-2011, 04:10 PM
I am studying the service manual now, I need to get these guys fixed.
One tries to come on and is variable by voltage and the other is just dead.

-John KF6DQU

09-14-2011, 04:28 PM
Unless you were Kenwood Service trained, why are you not calling or e-mailing Clif Holland at Avvid ?? -- Who was!!


09-15-2011, 05:12 AM
I have seen this once on a TM-V7 also, the fix was a new set of caps at power board, otherwise there was no problem. I would consider a fracture trace as well.

The one thing that strikes me, is the reseting of operations every time, to me this sounds like it could also be a bad memory power source or it is just failing.

The rest is for you to ask Clif Holland at Avvid, I have no more for help, but when you figure this out let us all know.

09-17-2011, 12:27 AM
my 742 just occasionally wont power on..Usually i just apply 120 ac to the power supply and it comes on..
but some times I have to flip power off, then hit power button while power is dying,, then power on.. seems if I catch the power at some lower than 13.8
the it will power up..

lately its been about one in 50 times it doesnt power on..so I just live with it..

I got this radio from a friend who bought it new but he could not get it to power on , hardly ever..
but if you find a fix I will be glad to try it..