PS1 mod chips and laser calibration

Oct 29, 2023 | Retro Gaming

I had been having issues with my childhood PS1’s for a while, one of them had a bad laser and the other started displaying grey scale only and the CD drive making awful noises. Figured I would finally address it.

Motherboard issues

Only one of the units had issues, it the 9000 series one. The board was totally fried so I got a donor unit from a mate that made a bad case, bad laser and a mod chip attempt that destroyed a couple of pins on the CD chip in the top right. I swapped over the CD chip from my board and restored it back to factory. It all powered up and kind of read discs ( laser was still bad ).


I opted for the MM3 modchip method as I had the programmers, the chips were cheap and still in stock at Jaycar, well not anymore as I bought the last of the stock. I used the PIC12C508A and the PIC12C509A chips. I followed the guide on William Quade’s Blog to do the install. He has documented all the possible boards and has the MM3 hex files for each chip and region you could want.

Laser replacement and calibration

The last step once I verified I had done the mod correctly was to replace the laser assemblies and recalibrate the new lasers. This was the most painful part of the whole thing as the trim pots are under the CD itself and are very fine adjustments. I started first with an Audio CD with 22 tracks to rough dial it in and then used a genuine game disc and the below guides to do the fine adjustments.

To do the laser adjustments, you need an old analog scope to be able to get the eye pattern, modern cheap and midrange digital scopes do not do this. It just takes patience but I got there in the end and actually modded and repaired a friends PS1 at the same time as all the gear was already out on the bench.

Laser Calibration references:
Alex Free’s Unofficial PS1 CD Drive Service Manual
Replacement Lasers


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