Hello,

I have a very old board where the microcontroller stage doesn't turn on. The power supply circuitry is okay. I then realized that one of the capacitors next to microcontroller crystal (4 MHz), like shown below, is kind of cracked up because of age. The marking code says 22J, so I guess they are 22pF. I don't have that value available right now, I just have 2200pF, 0.01uF and 0.047uF. I guess I will have to replace both of the capacitors to make them match. So, how do I determine if I strictly need the same capacitor value, or other values work?

 

You need a 22 pF capacitor; none of the other values you have will work. 18 pF may work, or 27 pF, or perhaps even 15 pF or 33 pF; but the values you have on hand aren't usable at all.

 

You need a 22 pF capacitor; none of the other values you have will work. 18 pF may work, or 27 pF, or perhaps even 15 pF or 33 pF; but the values you have on hand aren't usable at all.

I imagined it . Thank you. I'll see what I can do.

 

I've just found 27pF. I'll give it a try.