Hardware PS1/2 PS1 MM3 modchip not working - weird laser behavior

[IC_]

Hello. I've done one successful modchip install on a PSone already, as seen in my blog on this site (https://gbatemp.net/blogs/psone-adventures.19365/), and a while ago I got another PS1, model SCPH-1002 PAL version, to install a modchip for a friend, but this time I ran into some issues...
I'll try to not make this post too long, but basically, the PS1 still turns on normally, spins up and reads the disc, but just shows either the BIOS menu or an "Insert Disc" screen immediately afterwards. I'm trying to boot original legit Japanese-region games. I unfortunately don't have any original legit PAL games on hand to test.
Whenever the disc cover is open (the switch isn't closed), the laser starts really acting up, constantly jumping up and down in a seemingly random matter, to the point that it makes some audible clicking noises by doing that. The laser itself also does seem to repeatedly switch on and off while that is happening (definitely shouldn't happen with the disc cover open!). However, as soon as the disc drive cover switch is closed, whether there's a disc inserted or not, the weird laser behavior immediately stops and the drive starts working as if nothing ever happened, reading a disc if there is one inserted. An audio CD reads and plays normally, so I think the possibility of disc read issues can be ruled out. As far as I know, my friend also replaced the laser at some point.
The modchip is a multimode3.0 chip, bought from a local seller. I bought the OneChip for my PSone from them too, and they say that they test every chip on a test console before shipping it, so I don't think there should be any issues with that.
I've tried:
- reflowing all the modchip connections and making sure they are soldered accordingly with the schematics
- checking voltages on the chip's pins with a multimeter - the voltages are there and are variable on some pins
- inserting a burned tonyhax boot disc that works on my PSone
all without results.
I know I might be at a dead end here, but maybe this weird laser behavior can suggest what the issue is? Either way, I'd appreciate any help, since I've done everything I've thought of by myself and I've basically given up at this point.
@KleinesSinchen - maybe you'll know something about this.

 

[SylverReZ]

Hello. I've done one successful modchip install on a PSone already, as seen in my blog on this site (https://gbatemp.net/blogs/psone-adventures.19365/), and a while ago I got another PS1, model SCPH-1002 PAL version, to install a modchip for a friend, but this time I ran into some issues...
I'll try to not make this post too long, but basically, the PS1 still turns on normally, spins up and reads the disc, but just shows either the BIOS menu or an "Insert Disc" screen immediately afterwards. I'm trying to boot original legit Japanese-region games. I unfortunately don't have any original legit PAL games on hand to test.
Whenever the disc cover is open (the switch isn't closed), the laser starts really acting up, constantly jumping up and down in a seemingly random matter, to the point that it makes some audible clicking noises by doing that. The laser itself also does seem to repeatedly switch on and off while that is happening (definitely shouldn't happen with the disc cover open!). However, as soon as the disc drive cover switch is closed, whether there's a disc inserted or not, the weird laser behavior immediately stops and the drive starts working as if nothing ever happened, reading a disc if there is one inserted. An audio CD reads and plays normally, so I think the possibility of disc read issues can be ruled out. As far as I know, my friend also replaced the laser at some point.
The modchip is a multimode3.0 chip, bought from a local seller. I bought the OneChip for my PSone from them too, and they say that they test every chip on a test console before shipping it, so I don't think there should be any issues with that.
I've tried:
- reflowing all the modchip connections and making sure they are soldered accordingly with the schematics
- checking voltages on the chip's pins with a multimeter - the voltages are there and are variable on some pins
- inserting a burned tonyhax boot disc that works on my PSone
all without results.
I know I might be at a dead end here, but maybe this weird laser behavior can suggest what the issue is? Either way, I'd appreciate any help, since I've done everything I've thought of by myself and I've basically given up at this point.
@KleinesSinchen - maybe you'll know something about this.

Maybe the laser is on the brink of dying?

 

[IC_]

Maybe the laser is on the brink of dying?

As I said, I'm pretty sure it was replaced fairly recently, and audio CDs play just fine, so I doubt that can be the problem.

 

[SylverReZ]

As I said, I'm pretty sure it was replaced fairly recently, and audio CDs play just fine, so I doubt that can be the problem.

It could be that the chip was programmed incorrectly or because of the soldering. Do you have any spare 12C508 PIC chips lying around?

 

[IC_]

It could be that the chip was programmed incorrectly or because of the soldering. Do you have any spare 12C508 PIC chips lying around?

I've thought of that possibility as well, and I've thought of ordering another chip, but I don't feel like potentially wasting the money for that yet... I might end up taking that route if nothing else works in the end.

 

[KleinesSinchen]

the laser starts really acting up, constantly jumping up and down in a seemingly random matter, to the point that it makes some audible clicking noises by doing that.

It should not happen with cover open, agreed. Lid switch? Is something from the modchip connected with the lid switch line (detect disc swap for multi-disc games and inject SCEE after door open)?
You know, the only modchip I've ever installed myself is PsNee and that one monitors subchannel data to deduct if the read head is in lead-in area (and checks if the disc is not and audio CD) for injecting. With MM3 being the standard I'm sort of an alien, but the more modern ATiny chips + open source software I can at least understand a bit were the reason.

but maybe this weird laser behavior can suggest what the issue is?

Please look at the comment I added to my current status. https://gbatemp.net/profile-posts/158671/
That Wii drive which died during playing a legit DVD behaves exactly like that: Focus going mad, clicking. Drive still detects games, starts them but fails a minute or two later with generic the "An error has occurred" rubbish.

Trying to focus up/down and laser on/off a few times is normal procedure in detecting if a CD is present… but again: only when the lid closed switch is pressed. Infrared is visible as white dot in the lens in this short video:
https://gbatemp.net/data/video/382/382660-dc7c38b15018aaba7fc8e6436296d8b6.mp4
======

The process of elimination is hard here as you didn't check full functionality before disassembly – a mistake I've made recently myself, again with a Wii.
You could try loading a game from CD-R (and or the Japanese disc) by unlocking the drive with FreePSXBoot. If you can play Fear Effect for an hour the drive is probably okay – it tends to stutter on weak drives

Spoiler: This one

For testing purposes you should have some legit game discs at hand. Preferably some Fifa or other sports game shovelware you can get for pennies and you don't care for if they scratch up in testing (or PS2 consoles ruining them with the ribbon cable).