Post by gjaky on Jan 29, 2018 16:30:00 GMT -5
I throw this in, maybe you have some idea.
So there is this amplifier and the problem is from time to time (unpredictible: days, weeks, months) it thinks buttons are pressed while they don't. Not random buttons, but the problem is always with two certain buttons: up arrow and mute. The up button itself makes little harm during listening as it is only changing between EQ presets if present, but mute is obviously more annoying, especially because long pressing the mute turns the amplifier in standby.
The amplifier can be switched on as well from standby by long pressing the mute button.
And indeed all iterations have happened so far, concerning the bogus key pushing period.
The front panel hosts the 2x20 character VFD display, the remote sensor and the opto based rotary volume controller as well. A 40 pin flat cable is going from the front PCB to the main board.
The button sensing looks rather sophisticated: It looks like some of the data lines are tied to each button's first terminal, then when the button is pressed they are fed back to the main board after the buttons are "OR-ed together" with diodes (but there is also other gating going on). On the main board a freescale microcontroller is working, all connections are direct (I mean no further circuitry).
I've cleaned thoroughly all the boards and connectors -> no joy
I've even removed the switch itself -> no joy
I've sprayed freeze spray all over the surrounding components but could not reproduce the problem just by using the freeze spray.
Any ideas?
So there is this amplifier and the problem is from time to time (unpredictible: days, weeks, months) it thinks buttons are pressed while they don't. Not random buttons, but the problem is always with two certain buttons: up arrow and mute. The up button itself makes little harm during listening as it is only changing between EQ presets if present, but mute is obviously more annoying, especially because long pressing the mute turns the amplifier in standby.
The amplifier can be switched on as well from standby by long pressing the mute button.
And indeed all iterations have happened so far, concerning the bogus key pushing period.
The front panel hosts the 2x20 character VFD display, the remote sensor and the opto based rotary volume controller as well. A 40 pin flat cable is going from the front PCB to the main board.
The button sensing looks rather sophisticated: It looks like some of the data lines are tied to each button's first terminal, then when the button is pressed they are fed back to the main board after the buttons are "OR-ed together" with diodes (but there is also other gating going on). On the main board a freescale microcontroller is working, all connections are direct (I mean no further circuitry).
I've cleaned thoroughly all the boards and connectors -> no joy
I've even removed the switch itself -> no joy
I've sprayed freeze spray all over the surrounding components but could not reproduce the problem just by using the freeze spray.
Any ideas?
It is rather difficult to decide whether I did something to aid it or not.
