Initial fault: First power up at 12 and popped a 3A fuse. Visual inspection: Shorted SMPS Q104/Q103.
After multiple parts replacements, I can now power up the QMX+ with the current limited to 250mA. After applying power for about 5 seconds, the radio will self start up. Alternatively, I can touch Q105 on the SMPS and also make it boot up. The supply drops from 12v to 7.4V and the current limit is reached. The LCD is flashing a 6V low input voltage.?
I have replaced both AOD403’s on the 5V board and Q507 (shorted), c213 + r214 (shipped damaged/missing), two shorted BS170’s (changed the full set), diodes checked for proper operation.?
No solder bridges and all connections and solder joints verified.?
My suspicion is the 5v SMPS is still defective but what would cause the power on condition?
When I press the encoder to power off, the display shuts down but the voltage drop is still latched with current railing the set limit.?
Please advise any more items to check. I will order a replacement SMPS just in case but I would like to troubleshoot further if possible.?
TNX, Damon kc5cqw
