REPAIR GUIDE - TurboDuo/PC Engine Duo/R/RX: Laser Swap & Adjustment Guide

[Punch]

That's a good explanation for the stick laser problem.

I think I calibrated my Duo the best I could this time, and guess what, I'm able to play the full 72 min. audio from the CD I was using. The problem is when seeking later tracks (again). When playing from beggining to end it has no trouble.
Something very curious happens, in fact... Fast forward is very fast on the Edge of the disc (like if the CD laser was reading 300% better!). I feel like the problem lies with the "coarse" seek since mechanically when it tries to coarse seek a track, it overshoots a little bit then self corretct going backwards. It seems that it has no room for error in the Edge tracks so it ends up getting stuck.

My next purchase will be an oscilloscope or a Duo-RX.

[Keith Courage]

If it's too fast at the end or at the inner tracks try adjusting V101 slightly. The trick is to get a happy medium to where both the inner and outer areas can fast forward at about the same speed.

[tomiii]

Hello Guys, got the following Problems:

Got a broken PC Engine Duo and i switched all caps and one Vram (had some graphic issues, one via was broken but i fixd it).
Now i got a new Hop M3 Laser and now the test:
It only reads Music CDs (No game cds)
I try to fix it with the pots but not really anything happen.
Is this a Laser adjustment Problem (with Pots) or another Proplem ?

[blueraven]

The laser is probably out of focus. I would "put back" the pots to as close as stock and start with VR102, moving 1/16-1/8 of a turn each time until the CD's start booting. Use an ocilloscope if you have one and check the readings on the pots with a meter.

Did you change the caps that were under (below) the plastic hold-down for the CD player wires?

[tomiii]

Dear blueraven,

i adjust every pot with my ears except VR102.(dont have an ocilloscope)
Then i start with VR102 (just a little bit up) and the game cd are booting.
I testest 3 games and every game is playing now. From one Level to another level it take some time to load (maybe i need a finetune) but it works now .

Thank you blueraven

[thesteve]

if it plays cd audio perfect, its most likely bad cd work ram (the ram chip near the controller port)
any dead traces/vias around that ram would also do it

[cueball1897]

Adjusting the Pots:

Advanced Users/Modders only! (unless you really want to risk it...)

BEFORE YOU TOUCH ANY POTS, USE A THIN PERMANENT MARKER TO MARK EACH POT'S ORIENTATION.

Does this apply to the CDROM2 as well? Or are the pots labeled differently? My unit plays retail games fine, but I'm trying to get a demo level from a game I supported on Kickstarter to work. The CD-R works with MagicEngine, but not on my hardware. Thanks.

[blueraven]

Dear blueraven,

i adjust every pot with my ears except VR102.(dont have an ocilloscope)
Then i start with VR102 (just a little bit up) and the game cd are booting.
I testest 3 games and every game is playing now. From one Level to another level it take some time to load (maybe i need a finetune) but it works now .

Thank you blueraven

Glad you got it working! You're welcome, Cheers!

[blueraven]

Adjusting the Pots:

Advanced Users/Modders only! (unless you really want to risk it...)

BEFORE YOU TOUCH ANY POTS, USE A THIN PERMANENT MARKER TO MARK EACH POT'S ORIENTATION.

Does this apply to the CDROM2 as well? Or are the pots labeled differently? My unit plays retail games fine, but I'm trying to get a demo level from a game I supported on Kickstarter to work. The CD-R works with MagicEngine, but not on my hardware. Thanks.

BlueBMW has pointed out that the SuperCD Rom2 is so similar to the Duo that having a duplicate post would be redundant. The CDROM2, (white/black) however is completely different internally, and would take some fine tuning to get a bootleg or burn or demo working. I've personally tuned a few of them but it was so long ago I don't remember which pot to turn.

[thesteve]

the CDR2 is actually still the same chipset, and tunes much the same (with good laser)

[cueball1897]

would take some fine tuning to get a bootleg or burn or demo working. I've personally tuned a few of them but it was so long ago I don't remember which pot to turn.

That's good to know, I wasn't aware that the CDROM2 needed adjusting before it would read CD-Rs. I knew the media made a difference, but I was under the impression that they were just supposed to work.

[Mrwoodchuck]

Hi all,

I'm working on my pc engine duo this one has had some work done,
replaced all caps, ic502, cpu, cover switch, vr105....
After all said an done right now it loads card with no issues, cd's wont work.

I have got it where the disc spins, but after adjusting for about an hr the best i get is set disc, the worst I get is the disc don't spin..

I have a tektronix 2236 scope with a built in counter, the lowest the clock seems to hit is 4.4467 and then it goes back to the top..

Also the wave form tutorial is a little confusing. 
Pull the RF signal from pin 2 on the P5 connector, and ground it on pin 1 of P5.
so If i connect pin 2 to pin 1 the disc does not spin,but if i just put my probe on pin 2 and hit start I get a signal but it is super weak! approximately .25v pk-pk.

At this point I am thinking about buying a new laser, but at $20 I was hoping for some input first.

Thanks guys!

[thesteve]

.25V is too low
adjusting the focus and tracking pots will change the Vpp, so try that first (target is between .7Vpp and 1Vpp)
the pot on the laser will directly effect it, but too high and the laser fails (shouldnt need to touch it)

[Mrwoodchuck]

 Thanks for the reply thesteve,

That's what I assumed but was not 100% sure, as such adjusting vr102 and 103 did nothing really, it would increase the voltage but it was still maxing out at .25 any change would decrease the voltage.

I did break down and bought a new laser, it should be here today but that low voltage has me worried that it wont do anything to fix the situation.

Update,
That did it replacing the laser made it work with no issue. just did some adjustments after and bam loading perfect!
Thanks for the tutorial and help!

[Cordelay]

Hi there, I hope I don't break any rules reviving this post... :oops:

I recently adquired a PCE Duo with CD reading error; I've already cleaned the board thoroughly and changed all caps, also made sure (to my really limited knowledge) that they all work well, no lifted pads or broken traces, but cd doesn't even want to spin.
I've read that the first step before adjusting pots is marking the "initial" point to be able to go back to safe settings, but the thing is that the former owner of the console told me that he "adjusted" them already.

A forum member kindly told me that TheSteve and Turbokon made a couple videos showing how to adjust them using an oscilloscope, but I haven't been able to find them, and the thing is that I don't have the knowledge to start fiddling with an oscilloscope without a proper tutorial or guidance...

What should I do?

Thanks a lot for your help.