First post, by avxstudios
Hi folks,
Wondering if anyone could chime in on this particular topic.
I'm tinkering with a 486 system that uses a standard AT psu, (P8/P9 connectors)
The system seems to get unstable the longer it has been on, which suggests the power supply is not working right, I've measured the pins and get the following:
P9/6 : +5Vdc
P9/5 : +5Vdc
P9/4 : +5Vdc
P9/3 : -5Vdc
P9/2 : GND
P9/1 : GND
P8/6 : GND
P8/5 : GND
P8/4 : -12.2Vdc
P8/3 : +12.2Vdc
P8/2 : +3.4Vdc
P8/1 : GND/Power good
P8/2 is the one that raises an eyebrow, as when the system boots the line shows 3.4V, and briefly as the CRT (which is part of the system) the line jumps to 4.9V then back down to 3.4V, and if left running the voltage eventually drops to 3.2V at which point the system becomes unstable and crashes / shows artifacting, I don't believe this to be a heat issue as the CPU is well cooled, to me it feels more like the prolonged heat is knocking already out of spec capacitors slowly further out of spec as they heat up, and allowing it to cool somewhat reverses this.
I'm just curious as to if the P8/2 line should be as close to +5Vdc as possible or not?
Thanks folks.