Re: Short?


howard winwood G4GPF
 

The variable resistor sets the voltage on the contrast pin of the LCD, if contrast is not changing then voltage is not getting to R47 correctly, which could explain your hotspot.
I suspect a short somewhere in the vicinity of R47 or tracks that feed it.

On 24 Mar 2021, at 20:25, Mark <radiosportdx@gmail.com> wrote:

Hello all,

While trying to troubleshoot an lcd whose contrast doesn’t change with turning r47, I noticed a very hot spot on the main board underside where the 2x4 IU header was soldered. This happened on startup.
The solder points look good with no bridges.
Looking at the main board from the top, the header has
continuity from bottom left pin to one just above it. (Schematic shows they both go to ground??) should there be continuity?
If yes, how would one explain the hot spot?
If no, how do I remove the header without destroying it?
Please bear with me as I am a newbie at this. The qcx mini is my first intermediate build.

Thanks for your help,
Mark




Join QRPLabs@groups.io to automatically receive all group messages.