GM300 No Power?

Glenn · Post by **Glenn** » Thu Dec 09, 2004 10:07 pm

While messing around with my 16 pin connector on one of my GM300's, I think I accidently may have shorted something. I lost power to the radio so I think it's related. Is there anything I can check or a fuse to replace? Is it time for a repair shop visit or wheel chock? Any help is appreciated.

wa2zdy · Post by **wa2zdy** » Fri Dec 10, 2004 1:34 am

Sounds like maybe you popped the fuse in the ignition control line. It happens all the time, fear not.

Disconnect the power from the radio and check for continuity the positive pin of the main power connector and pin 10 of the accessory connector. If it's open, the fuse is open. You can just apply 12v to pin 10 along with the main power connector and your radio should work.

Pin 10 is the ignition control line. That would normally be connected (if desired) to switched power so the radio would go on and off with the auto ignition switch. (The GM300 doesn't like having the main power switched on and off like that. They do wierd things if you hook them up like that.)

Good luck.

Glenn · Post by **Glenn** » Sat Dec 11, 2004 11:53 am

Okay, I restored power to the radio by jumping out the fuse, but now have very low audio when turned up all the way. Radio transmits fine. Where is the audio power amplifier and is there a way to test it? I don't have a schematic available.

jackhackett · Post by **jackhackett** » Sun Dec 12, 2004 5:52 pm

The audio PA is that big chip on the logic board heatsink,should say something like TDA1519C on it.
Easist way to do a quick check is measure the voltage from ground to the outputs, pins 4 and 6. With the speaker disconnected and squelch open you should get around 6 volts on each one. If you don't it's probably blown...
Not a complete test, but it's a very good indicator.

Here's info on the chip:
http://www.semiconductors.philips.com/c ... 1519C.html