SCPH-7502 problem

[Roxilvio]

Hello everyone.
I’m gonna say this first, I’m very weak on the topic, everything I know was literally learnt today.
So, here’s the thing: I was doing some cleaning cause I wanted to restore and turn back “online” my old ps1 fat (7502).
While cleaning I accidentally moved ( with my fingers ) the laser trail, toward the disk socket. I also noticed I could not force it and move it back with my finger ( don’t know why it only moves in one direction, is that normal? ) so I had to move a little gear to take that back in position ( probably a wrong position, how do I know where to put that? ).
Now, while doing that, I had like a feeling I moved the laser trimmer. Don’t ask why, but I went touching that damn thing, and pretty much. I think a screwed up but I guess it’s still savable. The only problem is I don’t know the resistance I should be having by default ( or the one I had but I think it had never been changed until today, so default should fit ). My lens is a ksm440aem. I saw many people finding good solutions for the lens trimmer at around 1200ohm, other at 900. I don’t have tools like an oscilloscope and 100% I wouldn’t even be able to use it.
What should I do? Can I fix somehow? Would be better without replacing the full lens.
All of this happened because I felt like cds were scratching somewhere while spinning. Just to see if someone knows something about this.
Edit: I just remembered that I was forgetting something: the ps is “ modded “ I guess, I don’t know what kind of mod ( I was little when they did it ), and can read both original and burned discs.

[nocash]

Did you do all those things without ever testing if the console did still work (or perhaps it even still does work)?

The sled position doesn't matter, it does automatically move to innermost position on power-up.

The potentiometers, there is little chance that you could change them accidently without tools like screwdrivers.
But if you did do that: It might be helpful if you could explain what you did do there and why.

As far as I remember, there are several potentiometers (on the mainboard and on the drive unit), that brings up the question which one you are talking about, and how do you know that it is a laser trimmer.

I don't know what you want to say about ohms. Do you have a multimeter for measuring ohms? Did you measure them? Between which pins, on which potentiometer? Or did you mean that multimeters are falling into the "don't have such tools" category?

[Roxilvio]

Did you do all those things without ever testing if the console did still work (or perhaps it even still does work)?

The sled position doesn't matter, it does automatically move to innermost position on power-up.

The potentiometers, there is little chance that you could change them accidently without tools like screwdrivers.
But if you did do that: It might be helpful if you could explain what you did do there and why.

As far as I remember, there are several potentiometers (on the mainboard and on the drive unit), that brings up the question which one you are talking about, and how do you know that it is a laser trimmer.

I don't know what you want to say about ohms. Do you have a multimeter for measuring ohms? Did you measure them? Between which pins, on which potentiometer? Or did you mean that multimeters are falling into the "don't have such tools" category?

Sadly yes I was kind of scared, I thought I messed things up so I went quickly trying to recover because I had no idea of the consequences of touching that pod. Now of course I know, but it was different before.
Yes I'm talking about the laser trimmer to calibrate the laser power. I was just doing some cleaning, with a full disassembly you need to remove the whole lens machine otherwise you have no access to the main board. So I was just literally holding that with my hands and I guess I thouched that carelessly, but I wasn't sure though. I have a multimeter (analog, set up to 2000 ohms), I saw online where to test ( one on the top of the pod, one on the bot right). I didn't touch anything on the mainboard, I know there are two other trimmers to set some voltage stuff, but I honestly didn't think that could help.
Anyway since I don't know my default trimmer value, I tried setting it up at 1250ohm first, now i'm just trying around 1050. It reads original games and some burnt cds but many are like dead or taking way too long to load.
Now the big problem is that I am not sure if it is a faulty laser or faulty disks ( they are pretty old and I had them when I was a kid, so without much attention ). I also noticed this games are not well read on my portable dvdr reader on my pc.

[alexfree]

Did you do all those things without ever testing if the console did still work (or perhaps it even still does work)?

The sled position doesn't matter, it does automatically move to innermost position on power-up.

The potentiometers, there is little chance that you could change them accidently without tools like screwdrivers.
But if you did do that: It might be helpful if you could explain what you did do there and why.

As far as I remember, there are several potentiometers (on the mainboard and on the drive unit), that brings up the question which one you are talking about, and how do you know that it is a laser trimmer.

I don't know what you want to say about ohms. Do you have a multimeter for measuring ohms? Did you measure them? Between which pins, on which potentiometer? Or did you mean that multimeters are falling into the "don't have such tools" category?

Sadly yes I was kind of scared, I thought I messed things up so I went quickly trying to recover because I had no idea of the consequences of touching that pod. Now of course I know, but it was different before.
Yes I'm talking about the laser trimmer to calibrate the laser power. I was just doing some cleaning, with a full disassembly you need to remove the whole lens machine otherwise you have no access to the main board. So I was just literally holding that with my hands and I guess I thouched that carelessly, but I wasn't sure though. I have a multimeter (analog, set up to 2000 ohms), I saw online where to test ( one on the top of the pod, one on the bot right). I didn't touch anything on the mainboard, I know there are two other trimmers to set some voltage stuff, but I honestly didn't think that could help.
Anyway since I don't know my default trimmer value, I tried setting it up at 1250ohm first, now i'm just trying around 1050. It reads original games and some burnt cds but many are like dead or taking way too long to load.
Now the big problem is that I am not sure if it is a faulty laser or faulty disks ( they are pretty old and I had them when I was a kid, so without much attention ). I also noticed this games are not well read on my portable dvdr reader on my pc.

I read somewhere to never ever measure the resistance of the laser diode because measuring it damages it so you might need a new drive at this point. The only thing you should do with that screw is 'blindly' slightly move it for a pot tweak (use a marker to mark the original position please), but that should be the absolute last resort. Most of the time it is just a lubrication issue, or CD-R media/CD-R burner quality issue.

[Roxilvio]

Did you do all those things without ever testing if the console did still work (or perhaps it even still does work)?

The sled position doesn't matter, it does automatically move to innermost position on power-up.

The potentiometers, there is little chance that you could change them accidently without tools like screwdrivers.
But if you did do that: It might be helpful if you could explain what you did do there and why.

As far as I remember, there are several potentiometers (on the mainboard and on the drive unit), that brings up the question which one you are talking about, and how do you know that it is a laser trimmer.

I don't know what you want to say about ohms. Do you have a multimeter for measuring ohms? Did you measure them? Between which pins, on which potentiometer? Or did you mean that multimeters are falling into the "don't have such tools" category?

Sadly yes I was kind of scared, I thought I messed things up so I went quickly trying to recover because I had no idea of the consequences of touching that pod. Now of course I know, but it was different before.
Yes I'm talking about the laser trimmer to calibrate the laser power. I was just doing some cleaning, with a full disassembly you need to remove the whole lens machine otherwise you have no access to the main board. So I was just literally holding that with my hands and I guess I thouched that carelessly, but I wasn't sure though. I have a multimeter (analog, set up to 2000 ohms), I saw online where to test ( one on the top of the pod, one on the bot right). I didn't touch anything on the mainboard, I know there are two other trimmers to set some voltage stuff, but I honestly didn't think that could help.
Anyway since I don't know my default trimmer value, I tried setting it up at 1250ohm first, now i'm just trying around 1050. It reads original games and some burnt cds but many are like dead or taking way too long to load.
Now the big problem is that I am not sure if it is a faulty laser or faulty disks ( they are pretty old and I had them when I was a kid, so without much attention ). I also noticed this games are not well read on my portable dvdr reader on my pc.

I read somewhere to never ever measure the resistance of the laser diode because measuring it damages it so you might need a new drive at this point. The only thing you should do with that screw is 'blindly' slightly move it for a pot tweak (use a marker to mark the original position please), but that should be the absolute last resort. Most of the time it is just a lubrication issue, or CD-R media/CD-R burner quality issue.

Damaging seems a little bit too much imho ( I mean, it's just a multimeter ).
What I knew was more likely that the measure is not accurate, since you should work that out with an oscilloscope to get the correct value and the correct "setting", that's why it's not the best option. Actually I read also that there is an official Sony readable disc that helps you, with comunicating with the lense, to calibrate it ( it should give you like some sort of value ), but not sure, of course.
For the lubrication issue, I honestly disassembled the whole unit, cleaned all the gears and rails but i had no idea what to use to lub that ( some user on reddit said no WD-40, that would have been my way to go ).
As I said on the OP, the problem in a few words is that I lost the "marked default spot" since it was probably changed before I could even mark it.

[alexfree]

Sadly yes I was kind of scared, I thought I messed things up so I went quickly trying to recover because I had no idea of the consequences of touching that pod. Now of course I know, but it was different before.
Yes I'm talking about the laser trimmer to calibrate the laser power. I was just doing some cleaning, with a full disassembly you need to remove the whole lens machine otherwise you have no access to the main board. So I was just literally holding that with my hands and I guess I thouched that carelessly, but I wasn't sure though. I have a multimeter (analog, set up to 2000 ohms), I saw online where to test ( one on the top of the pod, one on the bot right). I didn't touch anything on the mainboard, I know there are two other trimmers to set some voltage stuff, but I honestly didn't think that could help.
Anyway since I don't know my default trimmer value, I tried setting it up at 1250ohm first, now i'm just trying around 1050. It reads original games and some burnt cds but many are like dead or taking way too long to load.
Now the big problem is that I am not sure if it is a faulty laser or faulty disks ( they are pretty old and I had them when I was a kid, so without much attention ). I also noticed this games are not well read on my portable dvdr reader on my pc.

I read somewhere to never ever measure the resistance of the laser diode because measuring it damages it so you might need a new drive at this point. The only thing you should do with that screw is 'blindly' slightly move it for a pot tweak (use a marker to mark the original position please), but that should be the absolute last resort. Most of the time it is just a lubrication issue, or CD-R media/CD-R burner quality issue.

Damaging seems a little bit too much imho ( I mean, it's just a multimeter ).
What I knew was more likely that the measure is not accurate, since you should work that out with an oscilloscope to get the correct value and the correct "setting", that's why it's not the best option. Actually I read also that there is an official Sony readable disc that helps you, with comunicating with the lense, to calibrate it ( it should give you like some sort of value ), but not sure, of course.
For the lubrication issue, I honestly disassembled the whole unit, cleaned all the gears and rails but i had no idea what to use to lub that ( some user on reddit said no WD-40, that would have been my way to go ).
As I said on the OP, the problem in a few words is that I lost the "marked default spot" since it was probably changed before I could even mark it.

I read somewhere that the electricity itself from the multi-meter damages it, and I kind of can confirm this because I used to do this and it did appear to make it all of the sudden worse. I don't know if this is placebo or all bullshit, I'd love to here what no $ has to say. Using an oscilloscope would be completely different I think (which I have not looked into at all.

You absolutely need grease and lube on the gears, I wrote down my method here: https://alex-free.github.io/unofficial- ... ce-manual/

[nocash]

I still don't understand if or how you could ever have changed the potentimeter. Those things things don't change their position when you "may have touched" them. I don't trust your judgement - I am almost sure that you have never changed the potentiometer setting. Unless your definition of "touching" is something like "cleaning it with an 800W electric tooth brush".

Cleaning could also be the problem, in case you have wiped off all oil and lubrication without adding anything new thereafter.

Better forget about CDRs for testing, old ones may have decayed, and freshly burned ones might have problems if the disc, burner or burning speed wasn't optimal. Better stick with original retail discs (unless you know that your CDRs did work well until last week, or still do work on other PSX consoles).

Measuring ohms with an multimeter does inject a small test voltage. That test voltage is strong enough to light up a reqular LED. If you have much more fragile components then it could also destroy them.
BUT, we are talkting about measuring the potentiometer, not about measuring the laser diode. So I would tend to forget about such issues, don't worry about it (unless you do actually know for a fact that the potentiometer voltage will also directly leak into the diode and destroy it).

[alexfree]

I still don't understand if or how you could ever have changed the potentimeter. Those things things don't change their position when you "may have touched" them. I don't trust your judgement - I am almost sure that you have never changed the potentiometer setting. Unless your definition of "touching" is something like "cleaning it with an 800W electric tooth brush".

Cleaning could also be the problem, in case you have wiped off all oil and lubrication without adding anything new thereafter.

Better forget about CDRs for testing, old ones may have decayed, and freshly burned ones might have problems if the disc, burner or burning speed wasn't optimal. Better stick with original retail discs (unless you know that your CDRs did work well until last week, or still do work on other PSX consoles).

Measuring ohms with an multimeter does inject a small test voltage. That test voltage is strong enough to light up a reqular LED. If you have much more fragile components then it could also destroy them.
BUT, we are talkting about measuring the potentiometer, not about measuring the laser diode. So I would tend to forget about such issues, don't worry about it (unless you do actually know for a fact that the potentiometer voltage will also directly leak into the diode and destroy it).

What I think he is doing is setting the multi-meter to ohms and measuring the resitance by putting postive on the point with the arrow in this pic:

LaserAl5.jpg

and the negative on ground, i.e. the metal sheilding above the motherboard. That's what this page explains to do (and I used to do). My understanding is this would be sensitive enough to actually damage the diode so I stopped messing with reading the resistance completely. Do you think there is no chance it will cause issues? I can't remember where I read this I am trying to find it but I always assumed better safe then sorry and also it almost never is the real issue.

[Roxilvio]

I got it, I'll try not to go too hard on that. The bad thing is I already tested many times.
Just a little different, I had positive on the point as shown in picture and the negative on another point right under the pod, bottom right. Anyway I'm gonna give a look at your method, I'm gonna see first if I got some grease here at home I can use and then I'll give it a shot.


Anyway as I said in the op, I wasn't even sure i changed the pod position, but I was not experienced, was also tired that day, so I took the wrong decision trying to bring that to a default position. After a few attempts of moving it I noticed I had just made a bullshit and then well, panic. I mean I agree that's pretty hard to turn that little knob just by accidentally touching it, but in that moment I wasn't thinking well. Now I know for sure I just calibrated that for no reason, and eventually it wasn't needed. I didn't go pretty much delicate while cleaning, didn't go with a "tooth brush the destroyer" but with full strenght compressed air just to remove most of the dirt and dust, ofcourse i didn't hit too hard on delicate components like the optical drive and others on the PSU.
Anyway the strange thing is that I got some CDR discs that works pretty fine, others are completely dead.
My original games are running well, but I wanna go deeper in that: today I ordered and I'll receive some fresh new CDRs (Verbatim, they say should be fine) and a memcard, so I'll keep on testing.
Like i'm gonna do an easy example, I had a working copy of Crash team racing: some tracks work, I found one that gets stuck on loading screen when selecting it. So I wanted to try a brand new burnt CDR ( tried with CDRW but, as i said, had no idea PS wasn't capable of reading CDRW )
Now I'm not too sure about this, but I read that the potentiometer voltage should be actually mV ( so not even that much ). Anyway as I said, my goal is to save this beatiful treasure of the past so I'll proceed being more careful.
Thanks again both, everything you typing is just bright light in a dark tunnel for me. I'm learning a lot.
Now I just got to check what lube to use for the gears and the rest of the drive.