I acquired a budget-priced GX4000 console, having been informed it was in working condition. However, the reality was a bit more complicated. The video display was significantly distorted, appearing blurred and seemingly out of sync. Initially, I suspected the culprit was the SCART cable, but testing this yielded no improvement.
Upon closer examination, I noticed signs of prior tampering. It appeared that someone had attempted to remove the 7805 voltage regulator. My measurements revealed that both the input and output were registering at +8.5VDC, which was abnormal. After removing the damaged 7805 regulator, it became apparent that the previous repair attempt had also damaged the board. The vias connecting to the regulator pads were torn out.
As the original 7805 was faulty I replaced the 7805 regulator with a new/old one and this didn't resolve the issue; the 8VDC persisted on both sides of the regulator. Further investigation revealed that Diode D183 (1SS132) had short-circuited. This explained why the 8.5VDC was passing directly through the system. It's rather astonishing that this didn't cause more damage to the GX4000.
With the 1SS132 diode unavailable, I substituted it with the nearest in spec that I had here, a 1N4148 diode, which brought the console back to life. ;D
My next steps involves replacing the 7805 regulator with a more efficient DC-DC equivalent, mending the damaged pad vias on the board, and obtaining a replacement 1SS132 diode. Given that D183 acts as a shunt diode, I'm optimistic that the DC-DC 7805 replacement might obviate the need for D183 altogether. DC-DC converters are generally more efficient than 7805 linear voltage regulators, often equipped with built-in protection mechanisms.
Also, some how I just lost the photos of this work :picard: , but I am sharing this work should anyone else have the same issue in the future.
I will keep this post updated.
Just a long lost follow up.
This mod worked very well, however I did mange to source some 1SS132 Diodes just to ensure all works as it should.
It also means the GX4000 does not get warm anymore.