Ceramic disc caps question

Rrcade

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This is a quote from braze tech. web site regarding pcb repair:

Other things to check for while you are inspecting the board include burnt edge connectors, burnt components, broken components such as capacitors and resistors, and of course missing components. Note it is very common for boards to have unpopulated chips, so don't assume any empty socket means a missing component. Check the schematic. Also, TTL designs require that there be a capacitor (usually a disc capacitor) every so often (sometimes as often as each chip), and they need to be nearby each chip. Anyways, it is common to see one or two of these capacitors broken. I usually don't worry about this right now, and usually don't replace them. However, for broken disc capacitors, I usually just remove the entire capacitor and mark the area to remind me that I removed it. This prevents a possible short-circuit which can occur if the broken disc capacitor happens to have the metal plates inside it touching each other.

What I get from this is that the ceramic disc caps AREN"T necessary? Can someone explain this further, as I'm about to replace a bunch of broken ones on some Midway SI boards, and now am wondering if it is Really necessary.
 
The caps you refer to are those that are strung between the ground and +5 volt lines, their function is to smooth out any ripples and ugliness in the supply voltage and are usually refered to as 'smoothing caps'.

Depending on the power supply these caps may be more or less necessary, a board with no smoothing caps at all may still run perfectly, but the more you have, the more consistent the voltage will be.

Not every ceramic cap is a smoothing cap though, some will be used for other purposes like audio or XTAL circuitry, and electrolytic caps are sometimes used as smoothing caps aswell.
 
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