Sega Saturn early Model 1 NTSC - Disc read issues

OK. I'll throw this one at the forum.

Early NTSC Model 1 Saturn - power supply in the top shell piece. Saturn powers up, clean video, motor spins the disc, laser tries to read/seek and the disc isn't found.

This problem is despite replacing the laser in the unit with a new one - basically the same problem the old laser had happens with the new laser.

Wondering how many of you guys have worked on this model or with lasers in general. I shouldn't have to adjust the laser pot on a new laser as it was set at the factory. I suppose I could mess with some of the adjustment pots for focus error, etc, but...really?

Unit seemed untouched inside. I have a multimeter and oscilloscope at my disposal. Open to any thoughts, measurement requests, etc, you guys have.

 

The cd tray spindle is often moving down over the years on Saturns, causind disc read errors, as the laser cant focus with not enough space between disc and laser. Try to move it up carefully.

 

Those early CD drives are quite critical - you shouldn't have to adjust the pot on the optical pickup, but it's possible that the servo adjustments on the drive board might need changing. The first thing I would try is to put the optical pickup into one a later model Saturn and see if it works, since they have automatic servo adjustments - if it doesn't work there then it's probably just bad, even if it's new.

 

Great information guys. I do have a functional later model, circle button Saturn in my current gaming setup. Perhaps I can drop the lens in there and see how it does.

As for the spindle - It seems to be just fine when looking at it from the side (spindle -> lens distance)

There is a part of me that is immediately wanting to "lalalala" the idea that the "new" laser is bad. The laser arrived with the anti-static protect already desoldered.

 

Saturn spindles dropping down is rather common.
Unfortunately, I don't know what the correct height should be.

 

So great news, guys - I got a chance to spend a bit more time with it and elected to tweak pots. There was quite a bitter of lens chatter when it was attempting to read discs - audio CD or game CD. Neither one worked. I did just the absolute smallest counterclockwise turn to the EF pot (between 1/16 and 1/8 of a turn), and elected to throw a game at it immediately. The chatter was gone, the drive was super quiet, and Nights into Dreams booted immediately.

Note to yesterday's self - Yes, really.

 

wait up, i got the default settings from a lot of model 1 compared for the servo adjustments on the drive board like @TriMesh mentioned.

i#ll go upload the pictures of my notes.

and pls stop setting the pot without proper multimeter readings of the ohms you set.


EDIT: ok i cant upload a picture, dont know why but its easy to write down and understand.

starting with the pot/ servo adjustment on the back, going to the front.

Pot - Setting 1 - Setting 2
X1 - 7.79 K ~ 11.57K
X2 - 10.46K ~ 8.88K
X3 - 16.15K ~ 9.35K
X4 - 6.17K ~ 6.42K

I had several Saturns where the new laser always read the disc as audio cd on any ohm setting.
After adjusting the pot/ servo adjustment on the back (X1) in this range i wrote, the laser would read every game just fine

on Model 2 there's only one pot/ servo adjustment and it reads 15-18K

 

You can use a multimeter to check your default values if you'd like to have measurements to return to should you need to reset to those starting values, but a multimeter alone is not very useful for making minor adjustments to a CD lens. Unless someone else has done serious tweaking to the pots and a general position reset is needed or you are checking for a bad pot, the ohm readings don't mean much at all.

There aren't really any exact values to adhere to because the models are going to vary as there are definitely different CD units inside the various models of the Sega Saturn. Your example shows a range to stay in, but you'll also notice that I never went past 1/8th of a turn in either direction on my changes.

The proper way to make the adjustments is to use an oscilloscope with the appropriate test CD and follow the calibration guide in the Sega Saturn service manual. I have a scope, but I don't have that CD. In other cases (such as the lens in the Turbo Duo and Duo-R), I have used the scope to check out the eye pattern to see if the values are up to spec while using a random audio CD, and ultimately had to do the remaining tweaks by ear.

I put a new laser into the Saturn. If you replace the laser, you will need to verify and possibly change the values of those pots. The Sega Saturn service manual actually says that right after replacing the lens is to walk the values and adjust pots as needed, check the eye pattern, and repeat as necessary. For some reason, my brain didn't want to confront this reality when I originally posted this thread.

I didn't get so far as needing to use the scope (which you can also use to determine if your lens is bad right from the start) as I only needed a minor tweak to one of the pots to get the game to fire up.

 

lol whut?
of course the ohm readings matter, not only the settings the diode was shipped with.
and you dont adjust the lens, you adjust the voltage that goes to the diode.

of course there are exact values, but not for the servo adjustments. i had so many Saturn going through my hand that no one could tell if they had factory setting or someone already screwed around on the servo pots and laser diode pot.

i already did the calibration with an oscilloscope, but its only of use for very fine tuning and not a common method to use for everyone.
tuning with audio disc and "hearing" if it plays right is also a quick solution, i did that often on Playstations with a cleaning disc that you have to push to the last track so it cleans over the first few tracks.

you cant go with the sega official manual when it comes down to third party/ aftermarket/ refurbished lasers. i had so so many in hands and tested on a lot of Saturns and various drive models, they had all the same outcome that the laser diode is crap and it doesnt do shit readjusting the servo pots if they are in range.

 

<shrug> I have adjusted several lasers and never cared about the ohm values. And by "adjust lens" or "adjust laser," I simply meant the general calibration and various pot tweaks that go into it. But hey - there are various ways to do it, so people just go with what they prefer. In fact, most resources I have seen (for game-based machines) are based on adjustment by ear alone. Ha! I would prefer a more precise way to set the values via a scope rather than by ear, but there aren't many service manuals kicking around for something like a Turbo Duo. I just wanted to see if there were any extra potential Saturn-specific issues with this thread, and items such as the info about the spindle is good back-pocket information.

 

Saturn spindle height is 39.66 to 39.67 mm using a caliper from laser PCB on my working Japan Saturn. I covered the PCB with a single piece of kitchen wrap to prevent scratching the board. I will measure the distance from the metal cd deck to spindle surface the disk sits on next time I'm working on the console. I find very little repair advice out there on proper repair info, and procedures to fix them..For the most part it's try this try that, seems counter productive to me. Information is only useful if based on fact and procedure . Nice work DragoonC actual facts...