MCR Troubleshooting.

@cdjump I am chasing cause of f1 fuse blowing on PS board in Spy Hunter. It boots and runs for 10-15 seconds.
- It happens in with 2 different PS boards and they both work fine in Tron so unlikely it is the PS board.
- I have likely narrowed it down pcb stack as I have everything (cheap squeak, lamp, coin door, etc) plugged in except pcb and it doesn't blow.
- caveat, not sure the lamp board is doing anything if not activated by pcb.
- however, with just pcb plugged in, it still blows so back to pointing to pcb.
- I then added 1 amp load on 5v line and it doesn't blow and ripple voltage is low on +5v line. I could add more artificial load too.
- Disassembled the board stack, measured resistance between +12 and +5v rails to associated gnd; there are no obvious shorts on either rail.

Am I missing something?
What size fuse are you using?
Also did you by chance replace the 9 pin molex on the 90412? edit - i guess not, if it works in a Tron.
I'd try a 1 amp fuse. SH draws more current than Tron does, by a good bit. I think there was a service bulletin about it.
 
Last edited:
What size fuse are you using?
Also did you by chance replace the 9 pin molex on the 90412? edit - i guess not, if it works in a Tron.
Curious, what was your thought here? mixed up the connectors?
I'd try a 1 amp fuse. SH draws more current than Tron does, by a good bit. I think there was a service bulletin about it.
Thanks for the reply. It had 3/8 amp fuse in it for the longest time till it just went kaput. I put in 1/2 amp (I guess known "upgrade/change" based on manual) and it blew as well. I will try stepping it up to 1 amp. I think the only thing that would pull amps through this fuse is q104, q105, and u2. load on 5v line putting to much stress on regulation ckt?
Anyway I will report back after upgrading fuse and putting boards back in.
 
Curious, what was your thought here? mixed up the connectors?
No, i had someone send me a 90412 one time that they rotated it 90°, and that was blowing fuses, i think it was on the suitcase, though, its been a while back. I thought that if its working fine in Tron, though, that's not the issue. I'm going to guess that it'll be fine with a 1 amp slo-blo.
 
Where to start.... I still have an issue with fuse F1 but found something wrong with both power supplies while investigating.
1) My "tron" ps had J5-12 solder bridged to 12v unreg common. I fixed that and Tron is much quieter, hum wise, now. doh!
2) My "spy hunter" ps had J5-9 (+12v reg) floating. This PS had major issues and I had replaced J5 long time ago. Guess that is why my lamps weren't working. Found this out by swapping into Tron and spinner wouldn't work. double doh!

Because the boards were out, I cleaned every board, chip, headers etc. and noticed that from the factory, they didn't have correct 24 pin socket at 10B & 12B so they hacked two sockets together. Doh by midway.

So finally back to fuse F1 on spy hunter. I still think something is bad on the pcb as the +5v starts at like 4.7v on pcb and then starts dropping. If I let it go it will just blow F1. I am going to try and narrow to one of the boards next. I am hesitating putting higher amp fuse in for fear of ruining damaging something on PS. going to poke some more but figured this was worth sharing.

edit> unplugged video and ssio board ribbon cables from cpu pcb and all other connectins (controls, video, etc) voltage is stable at 5v on cpu pcb.
plugged in ssio ribbon cables and voltage was steady at 4.9v
plugged in video ribbon cables and voltage is 4.6v and dropping like in video. Seems something is awry on video pcb.

edit2> pulled and tested all the sram on video board good. powered up video board on bench by itself and it is pulling 1.3 amps at 5v compared to both cpu and ssio together at 1.8 amps. No obvious shorts on 5v line as gnd to +5v is @ 280 ohms. hmmm

 

Attachments

  • 2025-09-20 12.47.55.jpg
    2025-09-20 12.47.55.jpg
    461.8 KB · Views: 6
  • 2025-09-20 19.16.24.jpg
    2025-09-20 19.16.24.jpg
    419.3 KB · Views: 5
  • 2025-09-20 19.14.57.jpg
    2025-09-20 19.14.57.jpg
    439.1 KB · Views: 5
Last edited:
plugged in video ribbon cables and voltage is 4.6v and dropping like in video. Seems something is awry on video pcb.
Did you replace the filter caps on the video pcb? Every so often, i see people do that, and bridge the +5 and gnd together. Could also be a failing 10uF tantalum cap. I've only seen one or two of them fail at 5v though. The ones that see 12v fail all the time though.

All of the 24 pin narrow sockets for the customs are 16 and 8 pin sockets. Every single one of them.
 
Did you replace the filter caps on the video pcb? Every so often, i see people do that, and bridge the +5 and gnd together. Could also be a failing 10uF tantalum cap. I've only seen one or two of them fail at 5v though. The ones that see 12v fail all the time though.
Nope. Board is completely original with no prior work. I will do more testing and checking. Might be red herring.
All of the 24 pin narrow sockets for the customs are 16 and 8 pin sockets. Every single one of them.
Interesting. These sockets must have been rare bitd.
 
Ok. Probably won't ruin this thread any more but figured I would post a correction and update. I will post when/if I finally figure it out.
1) the amps displayed and reported in post #64 were not accurate because there was too much voltage drop in my cheap cables. PCBs weren't even getting 5v in that test.
2) I wired up the board set on bench and it is working and stable (note switcher is rated at 20amps on 5v); no obvious shorts or unusual load so back to investigating power supply and/or maybe resistance in lines / connectors.

Pics with better amp draw per board measurement just in case it helps others.
CPU 2.4A, SSIO 1.2A, VIDEO 2A. That is @ 5.5 amps for 5v on just PCB.

Note. No sync combiner but it works good enough on pvm.
 

Attachments

  • 2025-09-28 17.11.11.jpg
    2025-09-28 17.11.11.jpg
    428.7 KB · Views: 6
  • 2025-09-28 17.10.51.jpg
    2025-09-28 17.10.51.jpg
    601.2 KB · Views: 6
  • 2025-09-27 17.32.07.jpg
    2025-09-27 17.32.07.jpg
    571.6 KB · Views: 6
  • 2025-09-27 17.28.24.jpg
    2025-09-27 17.28.24.jpg
    575.3 KB · Views: 5
  • 2025-09-27 17.19.31.jpg
    2025-09-27 17.19.31.jpg
    531.2 KB · Views: 5
Last edited:
Back
Top Bottom