SCPH-1001 intermittent disc reading

General information to do with the PlayStation 1 Hardware. Including modchips, pinouts, rare or obscure development equipment, etc.
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baraka
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What is PSXDEV?
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Joined: May 18, 2022
PlayStation Model: SCPH-1001
Discord: itsbaraka
Location: United States

SCPH-1001 intermittent disc reading

Post by baraka » May 18th, 2022, 1:38 am

Hi there, first off I'd like to thank this forum for all the help you guys have given so far. That said, I'm having enough of a rough time with my friend's old PS1 to make an account and post so here goes.

Basically I have an MM3 chipped PU-8 board PS1 that only reads official or burned discs on the first startup after being off for a while. At this point I'm fairly certain is has to do with the laser and pot adjustments, it was reading official discs fine there for a while but after adjustment it has a hard time with those now too. I've worked with a soldering iron in my hand everyday for the better part of 10 years now so I've tried a number of things so far:

- Recapped entire PU-8 board and verified capacitances
- Recapped power supply and verified capacitances
- New spindle motor/laser assembly
- Swapped old working laser into new sled assembly
- Multiple calibration attempts on bias/gain (I tried multiple values between +-0.1V off 1.70V bias and 1.85V gain)
- Vpp = 1 to 1.2V via scope on the laser pot, tried for both official and burned discs but reset back to ~1.1Vpp with laser at mid-disc on an official disc
- Multiple disc re-burn attempts with verbatim CDs (it managed to load Crash up to the level select screen once)
- Verified lens clarity and alignment

I suppose it could be an issue with the modchip but based on what I've read it seems more likely to be a disc reading issue, seems like something is heating/charging up somewhere and once that disspipates it has an easier time reading discs. It'll usually boot a game on the first start but then crap out a few minutes in. Below is a pic of my modchip installation in case anyone sees something wrong or if I soldered to the wrong trace somewhere but seeing as how burned games do boot I doubt it's the issue. I'd attach the full resolution pic but it's rejecting it for size despite it being under 3Mb, weird. I've found so little official service documentation so I've been going off user-reported voltages and tips but I'm kinda stuck for now and I'd rather not buy a disc drive emulator, lol. Any help is appreciated, thanks for reading.

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Studie
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Joined: Aug 16, 2023
PlayStation Model: SCPH-1001
Location: Japan

Post by Studie » August 17th, 2023, 7:06 pm

I've had the same problem on a similar board that I had, it also had a mod chip but eventually installing a PS1PSU ended up frying the thing and now I'm figuring out how to repair it.
I suspect the mod chip interferes with how the CD-rom reads. I bought multiple KSM-440BAM drives to try to solve the skipping and reading problems and it wouldn't fix.

I got to the point where I thought it was a faulty powersupply but then replacing the PSU with the PS1PSU 12v board ended up frying the diode on D301.

That being said, I should have tried removing the mod chip.
SCPH-1001

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