Sega Saturn Laser Calibration

Discussion in 'Modding and Hacking - Consoles and Electronics' started by KoroKoro, Sep 12, 2018.

  1. KoroKoro

    KoroKoro Member

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    I having issues with one particular Japanese white model 2 Saturn.
    The mod chip I have is known to work, as I have tested it in my other white jap model 2 - However they are not 100% the same. The working model 2 has a single main board and a 32pin JVC - the non-working machine is a smaller main board with a separate daughter board for the controllers. It also uses the 64pin chip on the CD unit.
    It currently plays retail pressed CD games, plays burned audio CDs fine. But when a known-to-be-working burned game is installed, the CD drive spins slightly then states that the CD drive is empty. Can't even play the games audio tracks.
    I have so far tried:
    • swapping CD drives (Can't read any disc)
    • all 3 combinations of the JVC/Sanyo jumper
    • confirming I am getting 5v and continuity of the ribbon cables
    • I have also tried using an old style mod chip - with all combinations of the 0014 / 0019 jumper. Still plays retail games and burned audio discs. Same behaviour with burned games - empty drive.
    Any idea how to get this working? Normally, I would just stick with using the working saturn, but unfortunately VDP has been damaged somehow as it is stuck in PAL 50Hz mode. The only alternatives I can see would be to swap in a working VDP2 or buy another saturn from Japan... I've just last night reinstalled the original VDP2 after an unsuccessful swap from another saturn (which turned out to be dead or incompatible)

    Thanks.
     
  2. Jei

    Jei Rising Member

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    A picture would be useful to identify but it’s likely to be a Sanyo drive.

    You’ll also need to remove the trap board
     
  3. VaNDAL

    VaNDAL Rising Member

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    The trap board ???
     
  4. 8bitplus

    8bitplus Gutsy Member

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  5. Bad_Ad84

    Bad_Ad84 The Tick

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    The removal of the trap board is documented in the installation manual too.

    Should be linked in both my sales thread and zer0s


    Regarding vdp being stuck in pal or ntsc, yes this happens. See my photo album on this forum for me doing the same job of replacing it. I likely have some spares from faulty boards too.
     
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  6. KoroKoro

    KoroKoro Member

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    The CD drive is a JVC ENR-011A. It appears it has also been used in some model 1s.
    [​IMG]
    Tonight, I've tried removing the mod chips. Ironically, it is exactly the same. Doesn't read burned games (drive empty) but reads burned CD audio.
    I swapped out the laser from the working machine. Still no change.
    I dug around and tried a sega CD that was burned with a different brand of CD-R. Audio played fine.
    So I burned a new copy of Xmen vs Street Fighter on the same brand CD-R. It is just a generic no-name brand.
    Now get this... Its decided to bloody work! It looks like my small library of burns don't work with this particular saturn. So I assume I will have to re-burn all of my backups? What's strange though is when I use my old copy of XM vs SF, it works maybe 20% of the time. But if I run another title then try running the same old copy of XM vs SF, it doesn't work at all 0%. Every other game I have burned with that brand of CD-R refuses to work with this machine.

    I think I may have had this same issue many years ago on another machine (32pin JVC). iirc it was 100% reliable after I replaced the old electrolytic caps with fancy tantalum caps. Though I probably just wasted money.

    Any ideas how to get my old backups library working with this machine?

    Thanks all for the help, guys.
     
  7. KoroKoro

    KoroKoro Member

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    Interesting. Last time I made a thread on another forum, no one had a clue and couldn't help me... So I just assumed this was a rare/unlucky faulty chip.

    It was a royal pain in the bum getting the chip out. I assume its all lead free solder. I used chip-quick. Never again. Massive pain in the bum. Difficulty level was right up there. Pulled a couple of traces as it was hanging on for dear life. Repaired the traces and installed the replacement chip. Bios didn't even boot. Swapped back the original VDP2... and no bios screen still. I thought I killed it good. Fast forward 12 months and I thought I'd try re-flowing the solder... glad to say I brought it back to life. Still stuck in PAL mode though.
    Next time, I'll be using my hot air rework station with the correct 4-port nozzle for this size chip. Should be easier now its got some lead in its joints too.

    You wouldn't happen to have any spare working VDP2s you're not using? I can't see any dead parts consoles on ebay at the moment. It would be nice to bring another machine back into full service :)
     
    Last edited: Sep 12, 2018
  8. TriMesh

    TriMesh Site Supporter 2013-2017

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    When you say it only works in PAL mode do you mean that it dies completely when you switch it to NTSC? If the latter, there are some PAL Saturn motherboards where the 50/60Hz select line is tied to ground on the PCB, so trying to switch it to 60Hz just shorts out the power supply.
     
  9. Bad_Ad84

    Bad_Ad84 The Tick

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    When I mean stuck, I meant with the leg lifted it still stays in 50hz mode.

    I used an IR BGA station to pull the chip. Easy.

    I can probably send you a VDP2, I have boards that people have botched the bios install. Rest should work OK.

    Also, saturn caps are failing quite a bit now. If this wasnt recapped, probably worth doing that.
     
  10. KoroKoro

    KoroKoro Member

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    I followed all of the traces and vias for the video mode circuit to make sure there was no funny business going on like shorting etc. It all checked out.
    I went as far as lifting the pin to isolate it completely. Doesn't matter if it's tied high or low - still outputs PAL signal. Being a Japanese console, it was native ntsc. I suspect it broke the first time I switched it to run my retail pal games.
    I'll PM you when I get to work about buying a VDP2 off you. Looks like your machine would do a much nicer job than if I were remove it by hand from another console. Those pins are very delicate and easy to bend out of alignment.
    I'll recap the system tonight and will let you know how that goes.
     
  11. KoroKoro

    KoroKoro Member

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    It also crossed my mind that there could be other variations between my consoles that I may have overlooked.
    1. Spindle height: I noticed it was a little bit low, but didn't seem to affect operation. Maybe the laser is borderline out of focus? Is there a spec from SEGA stating what the spindle height should actually be in millimetres?
    2. Variances with supply voltage/regulation to the laser - Under-performing PSU? Should I replace with a universal wall/brick switch mode power supply?
    3. Laser pots are out of adjustment. I understand I'll need a scope (got one), a service manual and a special test CD (A-BEC TCD-792A). Anyone know where I can find these?
    4. Also, anyone know where I can locate the test points on other CD drive board revisions? I only have the service manual for a model 1 PAL from 1995.
     
    Last edited: Sep 12, 2018
  12. KoroKoro

    KoroKoro Member

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    5. I'm probably miss-reading this but...
    Quote: "Check that the eye pattern waveform can be observed at the RF test point. (0.8-1.4Vp-p)"
    What is an "eye pattern waveform"? And where is the RF test point?​
    6. It shows I need to add a 10k resistor and caps to the test points. Can I just use my off the shelf probe (I assume has these inherently built in) Or will I have to make up my own custom probes with those specific caps/resistors soldered directly onto the test points and a homemade shielded cable connected to the scope https://www.jaycar.com.au/cro-probe-cable/p/QC1902

    (Sorry, I'm a noob when it comes to using scopes...:oops: but hey, I'm learning) ;)
     
  13. KoroKoro

    KoroKoro Member

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    Interesting development. Adjusted the spindle height. No improvement. Recapped the CD drive last night. Slight improvement. CD spins up but I can hear its having difficulty focusing. Some more games with this brand of disk are working, maybe 20% of the time after power cycling the machine.
    After inspecting the CD board for test points - unfortunately laser calibration is different on these drives to the one listed in the repair manual. So I'll need your help with this one.
    There is only one other maintenance task I hadn't done - So I thoroughly cleaned the lens with IPA. SUCCESS! All disc brands are now working. But it seems like it is still struggling a bit. Loading times are quite long and sounds like the drive struggles to read the disc sometimes. However, I find this behaviour to be quite strange, because prior to swapping the laser assembly, these discs worked fine in the 32pin JVC drive??? However, the same laser assembly swapped into the 64pin JVC drive was a no-go.
    So I think all of these symptoms are telling me the 64pin JVC drive is borderline out of adjustment and needs to be re-calibrated. So I'll need some help finding the correct service documentation and proper test disc.
    Thanks.
     
  14. Bad_Ad84

    Bad_Ad84 The Tick

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    Need to recap the main board too, not just the cd drive board.
    Also try swapping the PSU
     
  15. KoroKoro

    KoroKoro Member

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    Will do over the weekend. Plan to retrobright the case while I'm at it.
    Should I need to recap the power supply as well? I assume dirty power might cause trouble. My scope will only take 5v so I might not be able to safelt measure it? Measured 5.08v on my fancy multimeter. Or would I be better off replacing it with an external switch mode ps? I've noticed they tend to be fussy with power as my JP system doesn't like my 240v psu despite having the same pinout and current output (I should probably double check this)
     
  16. rama

    rama Gutsy Member

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    - You won't find the test disc but original pressed disks work just as well for what you can actually do with your equipment.
    - Some drive PCBs have markings like "TP" or similar on them. Otherwise, you'll have to guess where they are.
    You've never adjusted a laser? The eye pattern is the the analog signal that you get back from the laser assembly. There will be an amplified and the raw RF signal on the PCB. You want to measure the amplified signal.
    It has to be as sharp and well defined as possible, and be within the specified levels. I'd aim for 1.1V with these old lasers.
    [​IMG]

    Where did you read the bit about adding caps and resistors? I didn't see those notes last I tried fixing a Saturn assembly.
     
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  17. KoroKoro

    KoroKoro Member

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    I was afraid that would be the case...
    Nope. Well, not properly anyway... There is always a first for everything. And there is no better time to start learning than now :)
    I mean tomorrow ;)
    It's in the service manual. I assumed those white non-filled circles is where I connect my scope probes? Passive components (10k resistor + tantalum & ceramic cap soldered directly onto the board) https://console5.com/wiki/Saturn
    [​IMG]
     
  18. Bad_Ad84

    Bad_Ad84 The Tick

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    Also you can find the test disc. I bought one from taobao or something like that
     
  19. rama

    rama Gutsy Member

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    @Bad_Ad84
    Is it a newly pressed copy? The real test disks are hard to find items, but I suppose you could just press new ones.
    Depending on the type of disk, they may not have all the correct characteristics though.

    @KoroKoro
    Thanks for the link.
    It does look like they want you to use the extra components.
    The resistor looks to be for isolation, so your probing doesn't distort the signal.
    I'm not sure what the capacitors will do. They may bias the waveform to VC?
    In any case, remember that the service manual instructions are meant for a new pickup (quality assembly, too).
    Your readings will differ from the values listed, especially anything amplitude related.
    Just try to get the 0V offsets right and look for a good RF waveform.
    The RF readout is your best indication of a well adjusted drive.
    Also listen to the drive working. Avoid loud chirping or other unusual noises.

    (VC = Center Voltage. It's the reference level for most analog signals. Usually 1.25V or thereabouts)
     
  20. Bad_Ad84

    Bad_Ad84 The Tick

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    No, its not newly pressed.

    You can pick them up on audio forums easy enough too, as the discs arent console specific. (easy is subjective - easy to find, but cost reasonable money at times)

    I have a few different types and pick them up when I can.
     

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