28-11-2025, 03:13 PM
If you are still getting a low on pin 18 of the right hand 25 way pin strip (pin 1 is at the back of the machine, pin 25 towards the front, then have a look at both C43 (0.68uf) and C52 (2.2uF) on the coreboard.
After half a second or so of power on, both of these should have close to 5v on their +ve terminal. C43 in particular is notorious for failing at this age. If you see either of them showing a voltage of less than 4.0v
then replace them as they have broken down and have a low internal resistance. The values are not critical, and you can replace them with tantalum or electrolytic parts rated at 10v or greater.
Eg, for the 0.68uF you can use a 1uF - it will just mean that you have to hold the RESET key down longer when you want to reset the machine.
After half a second or so of power on, both of these should have close to 5v on their +ve terminal. C43 in particular is notorious for failing at this age. If you see either of them showing a voltage of less than 4.0v
then replace them as they have broken down and have a low internal resistance. The values are not critical, and you can replace them with tantalum or electrolytic parts rated at 10v or greater.
Eg, for the 0.68uF you can use a 1uF - it will just mean that you have to hold the RESET key down longer when you want to reset the machine.