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New 440BAM, setting the pots

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New 440BAM, setting the pots

Postby mrwedders » Mon Mar 20, 2017 6:51 pm

Hi all,

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?

Thanks all,
-- Ben
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Re: New 440BAM, setting the pots

Postby Biggsy666 » Tue Mar 21, 2017 7:38 am

If its a new laser (even a clone) it shouldn't have needed a pot tweak imo. For the ps1 i would only expect to do a tweak to prolong the life of a dying laser.
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Re: New 440BAM, setting the pots

Postby Thelonewolf » Tue Mar 21, 2017 8:22 am

The values will always differ to your own from guides, the ohm's are just optimal guidelines to follow (sweet spot for most). Thing is, some of those psx lasers are branded new, yet in reality are just refurbished ones, so you need to source them from the right seller.
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Re: New 440BAM, setting the pots

Postby mrwedders » Wed Mar 22, 2017 2:26 pm

Biggsy666 wrote:If its a new laser (even a clone) it shouldn't have needed a pot tweak imo. For the ps1 i would only expect to do a tweak to prolong the life of a dying laser.


I had been changing the pots with the original laser to see if there was any life left in that, so the two pots on the motherboard were probably offset somewhat. The pot on the laser flex was set to about 18mV out the box so it probably was set up for success, I was just concerned that the value seemed so much higher than what I'd read! So I turned it down and started tweaking upward again.

Thelonewolf wrote:Thing is, some of those psx lasers are branded new, yet in reality are just refurbished ones, so you need to source them from the right seller.


To be honest I was surprised by how much some people are asking for these things, I cheaped out and spent about £15. This PS1 won't see a lot of use anyway I'd just like it to be functional when I do wanna play it!

Thanks to you both for the responses, if you don't think these are crazy numbers I'll continue tweaking to improve the success rate, although it seems pretty good at it's current settings.
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