Here is a problem I just had with my Jurassic Park, I figured I would share here to help others:
Turned on the power and only had GI lights, and noted a slight acrid smell, so I turned it off quickly.
Checked the voltages on the power supply board in the backbox at the test points and found the 5vdc was ~2vdc, and noted whenever the power was on, I could smell the acrid smell in the backbox so I only left it on briefly to take measurements. (also the +12vdc was a little low, which makes sense, since the +12 is used in the 5v circuit)
I made some colored highlights on power supply drawing to follow what goes where.
Orange is the AC input.
Pink is the -12v rectifier output
Green is the +12v rectifier output
Blue is the output of the 5v regulator (IC1)
Red is the output of the 5v driver (TR5) after the regulator which is supplied by the +12v.
Purple was a mark I made next to each cap after checking it with my ESR meter.
Checking online, it was reported that a bad C2 will affect the 5v, but my C2 was previously replaced and tested good.
power supply 3 (resized).png
After confirming the Power supply board appeared good, I checked the 5v with the output cables CN5 and then CN6 unplugged and found the 5v was normal with CN6 unplugged which is CN17 at the CPU board. Likewise with CN6 connected and CN17 unplugged from the CPU board, the 5v was Ok.
With all cables disconnected from the CPU board it still loaded down the 5v when CN17 was connected, so the problem appeared to be on the CPU board.
There is only one electrolytic cap on the CPU board, C157, and the acrid smell appeared to be from that area. C157 tested OK with my ESR meter but when I removed it, I could see it was burned on the under side, and it smelled burned.
Replaced C157: 25v 470uF, and now the 5v measures 4.8v which I read is a typical value and everything is working with no issues. Back to C.H.A.O.S. as usual.