I turned it off with the QMX power switch. Earlier today it was exposed to more voltage for a short period of time but it was still working fine after that. I'm not very good at reading schematics but what measurements should I do?
When you turned it off and back on, did you do it with the switch on your power supply, or with the QMX front button?
?
Your symptoms are that you now have an internal power fault, which prevents the QMX+ from powering on.
One possibility:? If the input voltage from your power supply ever exceeded 14V, for more than a second or two, even with the QMX+ turned off, or if there was a high voltage transient from the power supply, it may have fused the input protection TVS diode (D110).? 13.8V on continuously for a period of time possibly could also damage that diode, which starts conducting somewhere between 13V and 14V.? There are of course other possibilities, only measurements will tell.
?
It will be best to turn down your voltage to about 7V and set a 250mA current limit while diagnosing this, if possible, to avoid any new faults.
Stan KC7XE
