OpenGD77

Hi, I have a problem with the GD-77 open. Something happened to the device. The device died.
I turned on the microphone and normally turned on the device when the device showed no signs of life. The green LED does not work. I tried to replace the battery in the hope that there was a fault in the battery, but the device still does not work. Of course when I turned off the microphone the situation did not improve and the device still remained dead. I tried everything and never brought it back to life. Do you have any idea about the mistake or what could be wrong. Before the last connection between the microphone and the device, the device worked perfectly and without any problems.

It sounds as if your hardware might have failed. There is an internal fuse which will blow if there is a fault with the radio.

If you can power the radio from a current limited 8.4V bench power supply you could check to see if it is drawing any current. If it isn't then it is likely the internal fuse has failed. Repairing or bypassing the fuse is unlikely to fix it, if the fuse has failed there will be another fault in the radio causing it.

I have seen this now on two GD77s. On one it was caused by a short circuit capacitor which was difficult to find but easily fixed. On the other it was caused by a blown audio amplifier chip. That was easy to find as it was burnt but it was not an easy fix.

You say that the radio failed when you plugged in an external microphone it might be that the audio amplifier was shorted out by the speaker plug and has failed. If that is the case the radio is probably not repairable.

Colin G4EML

Sorry, I don't remember which capacitor it was. The only memory I have was that it was close to the edge of the board.

Your only option is to trace out the shorted rail with an ohm meter and remove components until you find the shorted one.