what is this white stuff on board

[stevepaa]

So I am trying to get my color classic up and running.  I will recap the logic board but I was looking at power supply board and saw what looks like wax.  What is it?  I cannot seem to attach jpg ?

 

[olePigeon]

If it's a tough, but semi-soft white goop that looks like it was placed in various areas (kinda like a more resilient hot-glue), then it's likely an ESD & high-temperature safe resin epoxy that they use to secure stuff to motherboards.  Sometimes it's hard like a rock, though.  You'll sometimes see it blobbed in there to secure heavier components (or components that may vibrate) and keep them from becoming damaged from movement.  You can sometimes melt it with an iron, or if you can get a good grip with pliers, peel it off.  But you have to be careful not to pull off components as it could have solidified around leads or other parts that might catch.

I'm sure it has some official electronicsy-sounding name, but I don't know what it's called.

 

[rsolberg]

The product/goop I think you're looking at is often referred to as Silastic, Dow Chemical's trade name for the product.  It's a elastomeric silicone rubber/polymer used both to secure heavy components and support components that stick out from the PCB considerably, such as large electrolytic capacitors.  The product is used because it doesn't break down or melt, even with repeated thermal cycling.  Importantly, it's inert, unlike common acid-curing household silicone sealants that will corrode PCB traces and component leads.

 

[olePigeon]

That'd be it.