Cdm1250 backlight
Moderator: Queue Moderator
Cdm1250 backlight
I have a VHF CDM1250 50W dash mount and the control head backlight is not lighting. The LCD is fine. I swapped another head and that head backlight works so I have isolated it to the head. I have seated it Properly. All other functions and buttons are fine. Before I dig In to this are there any known issues on the head board and is there a pico fuse somewhere I can check?. I have the detailed manual but want to start here first. Thanks
I may not fire the first shot, but I will fire the last one.
-
jackhackett
- Posts: 1519
- Joined: Tue Jun 10, 2003 8:52 am
Re: Cdm1250 backlight
There are no fuses that would only affect the backlight. If everything else is working, including the TX/RX/Scan LEDs, I'd look at the backlight circuit itself. First look for any corrosion/liquid damage to the circuit traces, if that looks okay it could be a bad component.
One possibility would be a shorted C0843. The uProcessor outputs a PWM signal to charge that cap, and the voltage on it goes to the LED driver circuit to determine the brightness. The driver circuit is a regulator that senses the LED current through a couple of resistors, shouldn't be too difficult to troubleshoot with a voltmeter.
One possibility would be a shorted C0843. The uProcessor outputs a PWM signal to charge that cap, and the voltage on it goes to the LED driver circuit to determine the brightness. The driver circuit is a regulator that senses the LED current through a couple of resistors, shouldn't be too difficult to troubleshoot with a voltmeter.