MCR power supply on spyhunter keeps blowing fuse

Fuse

Start unplugging things like the Game PCB, Amp board, Etc and see if the fuse still blows on power up or use and Ohm meter between ground and the fuse holder to see if there is continuity without power to be safe. Then start disconnecting stuff.
 
That fuse is at the beginning of what ultimately becomes the 5VDC rail. Also, on a Spy Hunter...that fuse is supposed to be a 1/2 amp slo-blo. Disconnect the two larger connectors on the power supply board. These connectors send power out to all the other boards. This will isolate the power supply from all the other boards. If the fuse still blows...the problem is on the power supply board, or the transformer assembly. If all the fuses are the correct value on the transformer assembly....it's probably not your problem. The transformer assembly would probably blow one of it's fuses if it was the problem. This leaves the power supply board....and a lot of potential suspects. Looking at the schematics....D106, U2, or the regulators. Just the other day I had this same issue. I had the power supply board on my bench....since it kept blowing it's fuse, I couldn't probe it with power applied. Probing around the 5VDC circuit (with power off)....nothing jumped out. I got pissed at it and pulled out a 15 amp circuit breaker....alligator clipped it to the fuse holder, flipped the power on, and waited for the fireworks....there you go, C109 pretty much immolated itself. Problem found :). Now, I wouldn't exactly recommend doing this....the risk is kinda high for doing more damage, than not.

Edward
 
Thanks Edward for the info it gives me a starting point. I did disconnect the two large connectors on the power supply board and the fuse still did blow so I guess the problem is either the power supply board itself or the transformer assembly. I didn't get much time to work on the game so I will have to take a close look at the fuses on the transfomer assembly with my mulitmeter to see if any are blown. I'll keep you posted.
 
I couldn't probe it with power applied. Probing around the 5VDC circuit (with power off)....nothing jumped out. I got pissed at it and pulled out a 15 amp circuit breaker....alligator clipped it to the fuse holder, flipped the power on, and waited for the fireworks....there you go, C109 pretty much immolated itself. Problem found :). Now, I wouldn't exactly recommend doing this....the risk is kinda high for doing more damage, than not.

Edward

Was that one of my boards? LOL Cheater :)
 
Well I had a 1 amp slow blow fuse handy so I put it on the mcr power supply board to see what would happen. Turned power on and the 1 amp sarted to glow orange but before it blew the % amp fuse on the transformer assembly blew. I am thinking the problem is on the MCR borad and not the transformer assembly becuase when the mcr had a 1 amp fast blow it blew but nothing happened to the fuse on the transformer assembly. Does that sound right. I am going to test the diode at 106 becuase that is connected to the fuse and see if it is bad. If that diode is bad I assume it could be causing the fuse to blow?
 
Well I got the pwer supply MCR power supply working, I thought I would change the c109 like ELutz did on his board and bingo the fuse stopped blowing and I have 5v and 12v coming off the pwer supply. Now on to my next problem is that I am getting just a red and yellow picture on the screen and when I tryto coin up I get no sound. It's a spyhunter board and the led is not lite up. Time for a new thread.Thanks to all for your help.:)
 
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