Return of the (slightly less) faulty ZX Spectrum
Posted: Sun Dec 02, 2018 8:17 pm
A few weeks back I asked for help with a problematic ZX Spectrum (viewtopic.php?f=22&t=1107) and it was pretty much decided that the voltage regulator was faulty and that it might have damaged other components as well.
I've changed the regulator and the unit is now actually responding though not without glitches as can be seen in the picture I've attached. The glitches/artifacts appear after some button presses, though admittedly I can't test it properly as the keyboard ribbons are pretty crap and needs replacing. It sometimes also reset but I haven't been able to get a picture of that.
I've done the same tests as before and here's the results
The edge connector
Pin 3B/+5V: +4.94V
Pin 4B/+9V: +10.76V
Pin 20A/-5V: -4.9V
Pin 22A/+12V: +10.7V
4116 DRam
Pin 1-16: 0.004V
Pin 8-16: +9.95V
Pin 9-16: +4.94V
7805 Voltage regulator
Pin 1: +10.77V
Pin 3: +4.95V
Is it safe to assume that the previously faulty voltage regulator might have damaged the DRam chips?
I've changed the regulator and the unit is now actually responding though not without glitches as can be seen in the picture I've attached. The glitches/artifacts appear after some button presses, though admittedly I can't test it properly as the keyboard ribbons are pretty crap and needs replacing. It sometimes also reset but I haven't been able to get a picture of that.
I've done the same tests as before and here's the results
The edge connector
Pin 3B/+5V: +4.94V
Pin 4B/+9V: +10.76V
Pin 20A/-5V: -4.9V
Pin 22A/+12V: +10.7V
4116 DRam
Pin 1-16: 0.004V
Pin 8-16: +9.95V
Pin 9-16: +4.94V
7805 Voltage regulator
Pin 1: +10.77V
Pin 3: +4.95V
Is it safe to assume that the previously faulty voltage regulator might have damaged the DRam chips?