I was given a PS1 and a whole load of games by a friend who was clearing out, an SCPH1002. I figured it would be kinda neat to have a launch PS1 knocking about!
The laser mech was pretty much dead - as you would expect I guess. I had a go at fixing it but it never really got past the intro logos/cinematics of a game.
So I bought a 440BAM to replace it with which I'm assuming is a cheap Chinese clone. This arrived today and is installed.
My question relates to tweaking the pots to set the laser intensity/bias/gain. I used the guide from here (theisozone [dot] com/tutorials/psx/general/how-to-calibrate-a-ps1-scph-1001-laser-assembly/), but I ran in to a problem once I got to the gain pot - with the intensity pot set to 11.2~11.6mV and bias pot 1.69~1.72V, the system won't acknowledge there's a disc inserted meaning I can't set the bias pot under load like it says. I have to crank the first intensity pot up to about 16~17mV to get it to reliably read anything.
If I then try playing with the gain pot it doesn't seem to do anything. I've given it at least a quarter turn and played the same track on the same CD and read the exact same values from the test point. I didn't want to go further than a quarter turn in case something bad happened.
So at the moment I'm reading 17.2mV on the intensity pot, 1.702V idle, and about 1.735V while playing an audio CD. At these settings it seems to read the few discs I've tested pretty well.
Does anyone have any advice/guidance on why these values are so different to the guide? Or why the gain pot doesn't seem to do anything? I've pot tweaked a Gamecube to read backups before but that's about the extent of my experience in this area. It does look to me like the disc is sitting closer to the laser than with the original mech, and I understand these pots can affect the focal distance - could this be a problem?