Display turns off after 30 seconds or so

Discontinued products Shruthi
#1

I have strange problem with the Shruthi - everything works fine when I plug it first, the display comes on, sound works, midi etc. After half a minute or so, the writing of the display fades out - as if I had changed the contrast. The strange thing is that the display worked fine for the past few weeks, and only a few days ago this problem had come up, after I had cleaned the boards of the residual flux.

When I unplug and plug the Shruthi again, the display doesn’t come on, it goes directly to zero contrast. If I leave it rest for a couple of minutes, the display will work again for a short time - as if something needs to “cool off” before the display can come back. I wonder if something overheats and causes the problem. I have a 12V wallwart which delivers 12V accurately, but I can also mention that the 7805 gets really hot.

Any help would be greately appreciated!

#2

Maybe you have a small short. But it could also be that using a 9v adapter solves the problem.

#3

check the voltages after it craps out (+5/-5)

#4

A hot 7805 and fading out display is a good sign of an emergency-power-down in the regulator. When it gets too hot, it will shut down to prevent damage. The Shruthi is not designed to run from a 12V supply - test it with a 9V Supply or attach a big (!) heatsink to the 7805

#5

Indeed I suspected the 7805 to be the problem here, or the 12V supply. I’ll try with a lower voltage. Thanks a lot !