GME Fau Pa!! help needed tech issue

Where are you located?

I'm not a big fan of doing reverse polarity protection that way - it doesn't guarantee other PN junctions in the circuit will not conduct... anyway... the diode will probably be located very close to where the 12V enters the PCB. It'll probably be a 5 or 10A diode so should be pretty chunky even in surface mount form.

If the only consequence of the reverse polarity was to open circuit the diode and blow the fuse then once the fuse has been replaced the radio should work as the diode is, essentially, not there any more - just DON'T reverse it again until you replace the diode and ensure you use an identical once to the GME part - hopefully, but I'm not holding my breath, they will have chosen one with a low forward voltage.

Mike Harding

Did you have a suitably rated fuse in line? as generally the fuse blows before the diode, When you connect it up the wrong way current flows through the diode and blows the fuse. And when the diode blows it usually goes short circuit, if it's gone open circuit then the radio will still work it just means you have no reverse polarity protection anymore. The diode is only used for reverse polarity in normal operation it is reverse biased and no current flows.So if your radio is not working and it's not blowing a fuse every time you connect it up then the diode is not your problem. In 25 years of CB's I've destroyed numerous protection diodes and they all went short circuit and all went this way because there was no fuse in line or the fuse was a bolt.If the diode did go open circuit or it was just removed to get the CB going, had to get back to the YL's ASAP, the next time it was connected the wrong way there were a few bit's that got fried, in the old AM/SSB rigs it was the audio IC.
So if your radio is not blowing the fuse and it still won't power up there are more bits fired than the protection diode.

I've not had the pleasure of working on a TX4600 yet. But generally, GME does a good job with reverse/over voltage protection.
Usually a 16V zener diode is placed across the incoming supply, hopefully you had a properly rated fuse between the radio and the battery. This zener diode will blow the fuse on application of reverse polarity or over voltage (>16V).
50% of the time, application of reverse polarity blows the fuse and nothing else happens, a replacement fuse get the radio up and going again. The other 50% of the time, the zener diode goes short circuit and replacement fuses continue to blow.
If you have a multimeter, check for a short circuit between the red and black wires on your radio. If there is a short circuit, then you had best get it to someone that can replace the zener diode and check the rest of the radio.
If there is no short circuit and you are game, install a new fuse and hook it up (the right way around) and see what happens.
The GME TX3200/3400 series radios also had a small internal fuse (a circuit board track) that would blow if the user continued to fit bigger and bigger fuses until the zener diode cracked open and no longer provided protection. The TX4600 might have a similar internal fuse as well.
Surface mount components aren't really meant for people to work on them, I hate having to do the mod on the TX32/3400 radios for the new UHF output power module, the replacement resistors are the size of a couple of grains of sand!