The "pop" you heard was very likely an old dried up capacitor shorting and exploding. Any caps over 15 years old are suspect and NEED to be replaced. Other items like resistors should be checked for heat damage, or burn marks on the board.
The first thing you would want to check for in the set, are the capacitors visually, making sure none are bulged, swollen or leaking fluid. The picture at the link shows a leaking capacitor (a blown capacitor will literally have the side blown out of it and looks like a soda can that was shot with a shotgun):
http://www.google.com/imgres?imgurl=http://www.m ikerepairscomputers.com/blog/wp-content/uploads/2009/07/Bad_Capacitor_01.jpg&imgrefurl=http://www.mikerepairscomputers.com/blog/hardware/bad-capaci tors-your-computer/&h=600&w=800&sz=114&tbnid=JA6P6E-fpa5A1M:&tbnh=90&tbnw=120&prev=/search%3Fq%3Dfaulty%2Bcapacitors%26tbm%3Disch%26tbo%3Du&zoom=1&q=faulty+capacitors&docid=Jfij2k-0Zi2uuM&hl=en&sa=X&ei=PS67TrjyHa_KsQKfh4m8CA&ved=0CEIQ9QEwAg
Any that do not appear cylindrical, or are leaking you would take the rating (In uf), and the voltage off the cap (example: 2200 uf, 50 vdc), and cross reference them at the sites below:
They each solder into place with two leads, a positive and a negative. Make sure you solder the news ones in the same way, or they will explode when the unit is powered up.
Make sure you are careful not to un-solder any other adjacent circuit traces when removing the old caps, and carefully solder in the new ones allowing the solder to flow into the joint. Replace any and ALL caps that are questionable. Remember- when in doubt, change them out.
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