MM3 modchip soldering points?

Discussion in 'Modding and Hacking - Consoles and Electronics' started by StriderSubzero, Feb 22, 2018.

  1. StriderSubzero

    StriderSubzero Active Member

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    I have a SCPH-101 model PSOne/Ps1 Slim, and I'm not getting any power after installing the chip. I'm somewhat experienced in soldering so I had no issues soldering to specific points and have done mods in the past of this nature with no problem.

    I think I'm misunderstanding the diagram I found, though: imgur.com/a/336Yk

    On this diagram, it does not indicate pins 2, 4, or 5, so I soldered to points I found using another diagram for a different board. Should I instead desolder those points since they're not included in this diagram?

    The other question I have is, what is meant by the red circle pointing to the power jack and the red circle on top of the chip (to the left of point 8)? I did not solder anything to the power jack.

    I would appreciate any guidance here. Thank you!
     
  2. TriMesh

    TriMesh Site Supporter 2013-2017

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    OK, the first thing to check is that you have the correct drawing for your board (I.E., it really is a PM41(2) rather than just a PM41) since the pinouts are different.

    All the signals on that drawing look reasonable to me.

    Pin 1 is modchip power - shown going to the power pin on the boot ROM
    Pin 2 is an optional LED output and should be left open
    Pin 3 is the signal monitoring the comms with the CD controller
    Pin 4 is RESET/ - since the PSone doesn't have a reset button, i would tie it to pin 1
    Pin 5 is WFCK - output signal from the CD DSP
    Pin 6 is input to the tracking error amplifier
    Pin 7 is door switch
    Pin 8 is GND

    So I would connect 1, 3, 5, 6, 7 and 8 as shown in the drawing, leave pin 2 open and wire pin 4 to the same point as pin 1.

    I think you can ignore the red circles - my guess is that the drawing was originally for the PAL ONEchip and was modified for MM3.

    It's also worth checking the SMT fuses located at the lower left corner of the PCB (reference designations are PSxxx) and seeing if they appear to be blown.
     
  3. StriderSubzero

    StriderSubzero Active Member

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    Thank you, that's really helpful. I'll open it back up and double-check my board version.
     
  4. StriderSubzero

    StriderSubzero Active Member

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    Okay, so I've opened it back up. I actually have a PM41, but the good news is I used the PM41 diagram but I uploaded the wrong one above. This is the diagram I used: https://imgur.com/a/Xt2v3

    So I've followed your advice (disconnected pin 2 and wired 4 to the same point as 1) and unfortunately I still am not getting power. Here's a photo of my board/chip wired up: https://imgur.com/a/SBb8T Does it look like I've done anything wrong?

    One thing I wasn't clear on is checking the fuses. I'm like 90% sure I know what you're referring to, and they don't look damaged to me, but I'm not sure how to tell with that type of fuse.
     
  5. TriMesh

    TriMesh Site Supporter 2013-2017

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    OK, all the connections look reasonable. Unfortunately, those type of SMT fuses don't generally show any visual sign when they blow, and you need to check them with a meter. The simplest method is to power up the board and connect the -ve lead of the meter to the ground plane and then read the voltage on both ends of the fuses. If the fuse is good, then you will get pretty much exactly the same voltage on both ends - it you get something like 3.5V on one end and 0.8V on the other then the fuse is blown.
     
  6. StriderSubzero

    StriderSubzero Active Member

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    Okay, thank you for your help. Turns out one of the fuses was blown. For whatever reason my multimeter wasn't much help so I just bridged them with a wire one-by-one (I know...) and it powered up once I got the right one. My question is, how can I go about replacing the fuse? It's marked simply "20" but I'm not sure of the value and I can't find anywhere online that lists all the fuse values. I don't have much experience replacing fuses of this kind so I apologize if this is a stupid question.
     

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