This one was strange so we thought we'd share the knowledge. Customer was experiencing very poor audio - almost indecipherable - on certain calls and on voicemail greetings/messages etc. Tech realized the problem was only occurring when a VCM channel was involved. He pulled out the Combo Card and saw this strange black deposit on all the exposed copper; something we've NEVER seen before. He replaced the Combo card and the issue went away completely! Weird one eh?

This the only card in the system with the black deposits? Weird indeed.

If this is is evident on more than one PCB I would think environmental issues such as high humidity.

If this is ONLY on the one PCB I would think manufacturing issues such as delaminating, that is, the PCB wasn't properly laminated.