One segment of the display GCP less bright

Q & A for building and interfacing your rack gear with Ground Control Pro and GCX-based systems.
Vorg
Posts: 3
Joined: Sat Apr 17, 2021 12:43 am

Re: One segment of the display GCP less bright

Post by Vorg »

Alright, I ordered 2 new ULN2003 ICs and tried stacking one on IC10 and IC11, no results as shown here: https://youtu.be/mycn_GTLY5s .

I should add, though, that I also tried catching some voltages around the "core" PCB and found different values on some pins of IC10 and IC11. Suspecting something wrong there, I found R27 to be 1K and R28 to measure 500 Ohm while showing a small ding on one of its two legs. To my experience, it's unlikely for that to actually damage the resistor but since I was at it, I swapped that one with another 1K resistor (it's a carbon comp VS the blue metal film that was in that place but it doesn't matter).
Now I have both R27 and R28 rated 1K and albeit the problem stayed there, I noticed the flickering I had on that segment (progressively getting brighter and visible while supposed to be off) had disappeared. Maybe I'm getting closer to the real problem, but I don't have a schematic and don't know how many volts I should expect at each pin of IC10 and IC11. Perhaps anyone could tell me which resistor value you have in R27 and R28? Or maybe there's some other component involved that I should check?

Rico Coolen
Posts: 15
Joined: Wed Jan 27, 2021 1:21 pm

Re: One segment of the display GCP less bright

Post by Rico Coolen »

Looking back at my pictures, the resistors would be R27 - 1K and R28 - 10K

Image

Vorg
Posts: 3
Joined: Sat Apr 17, 2021 12:43 am

Re: One segment of the display GCP less bright

Post by Vorg »

Thanks, Rico! As shown in the pic attached (sorry for its quality, however I had the resistor checked with my multimeter prior to the installation), I installed a 10K metal film resistor in R28 but it didn't change much. I thought maybe having had 500 Ohm in that place could have "fried" the new ULN2003 in IC10 but then, again, I tried stacking another new ULN2003 on top of the one soldered and nothing changed. Checked back all solder joints on IC10 and everything seems to be alright so… what could I still check?

It also puzzles me not to receive a reply from any staff member at VoodooLab, they've always been very supportive before this issue but now it's months without a proper assistance, feels kinda strange.
Attachments
IMG_20210429_154733.jpg
IMG_20210429_154733.jpg (52.55 KiB) Viewed 3621 times

Post Reply