Thanks Paul. I realize that they may be blown, but from my recollection they didn't continue shorted. Low power out was the usual symptom IIRC. This is a complete short immediately on power on.

73,

Cliff, AE5ZA

On Aug 28, 2023, at 18:25, Paul - AI7JR <paul.hanchett@...> wrote:

Most likely culprits are going to be the BS170's, and possibly IC503, from other reports.

Paul -- AI7JR

On 8/28/23 15:32, Cliff wrote:

Well, guys, I'm up a creek it seems here. I'm an old guy, raised on Tubes, and don't really understand Mosfets and the schematics for the QMX are hard for me to follow.

Some suggestions to trace the issue here would be much appreciated.

I built this QMX about 3 1/2 months ago. It's been working FB with firmware 006 ever since. This morning I was using it and transmitted accidentally with no antenna attached. It's happened before with no consequences, but this time something shorted out big time. The power supply went into current limiting at 1 amp with the voltage dropped to 6 volts. Powered off with a BIG SIGH!

Opened it up and just a little smell of hot electronics, but not the usual burnt smell. Inspecting all the boards and nothing obviously burned.

Lowered the voltage to 7 volts and current limiting to 600 mA. Pushed the encoder to power up and nothing happens. Raised the power back to 12V and with one hand on the power off switch pushed the encoder. Current started climbing rapidly so power off quickly.

Tried to figure out the schematics and I get lost with all the plug numbers not being consistent between pages and some times I see multiple connector diagrams like JP101 and JP102 that seem identical as well as new to me symbols, etc. and Not really knowing how things work in the sequence I finally started this email.

Obviously something in the power up sequence has shorted, but how to trace it I'm totally at a loss.

Some help/ideas will be greatly appreciated.

Thanks!!!

73,
Cliff, AE5ZA