Help with N64 that won't power on? (No LED)

After taking apart a WORKING n64 to clean it, I put it back together and the power wouldn't come on. I suspected the PSU but it works on my 2 other n64's. I thought maybe I put in the expansion pak in backwards, but it still didn't turn the next day. I decided to try reheating the solder joints near the power plug on the MOBO and it turned on! But then when I went to put it back together it went back to not working. Reheated the solder joints again, it worked, I put it back together carefully, and again it stopped working after! No LED, no picture, no sound.

I have no idea what to do can someone help me out?

EDIT: So far I've discovered that the N64 works when the heatsink is off. It won't work with it on.

 

If the expansion pack is inserted backwards, all of its three different power rails (VCC, Vterm, Vref) short to ground – setting off one or more PSU fuses, as well as frying the RCP and RDRAM(s).

Did you tamper with the large aluminum heatsink/shield? Was the board bent or flexed when disassembled vs assembled with the PSU attached? Can the 6 pin power connector wobble?

 

Are you noticing any imperfections or anything of the sort on the case itself? When I RGB modded an N64 about a year ago with the RGB board I had an opposite issue. Colors looked super faded and the brightness was off, but once I put the console together it all worked perfectly.

 

EDIT: Okay idk how this part got left out but I just found out that the console turns on with the heatsink off, and it won't turn on when the heatsink is put in.

Something must have happened how that whenever the heatsink is added it won't work. The power connecter doesn't wobble.

The case itself is fine. Just found out the Heatsink is the issue.

Okay what do you guys suggest I do from here?

EDIT: Im a dumbass. A small metal part of the heatsink wasnt attacked the right way. Fixed and working!

 

With heatsink = console does not power on, no LED lighting up.
Without heatsink = console can power up normally and boot up games.

Did you by any chance use any fluids to clean the internals of the console?

The heatsink distributes its weight onto the cartridge slot, CPU, RCP, RDRAM, and memory expansion slot (with attachments). Adding weight onto these components (including tightening screws) seems to not allow the console to power on (if there was fluid present it would be squeezed out from underneath these components and onto neighboring pins?).

A multimeter continuity test would come in handy to see if 3.3V and GND or 12V and GND are shorted - a continuity test can be done while you press down on each: cartridge, CPU, RCP, RDRAM, and expansion slot - no need to keep PSU attached. Note all these components are quite densely populated with pins as well.

 

Well problem solved, didn't see the edit before making a posting.