Author Topic: REPAIR GUIDE - TurboDuo/PC Engine Duo/R/RX: Laser Swap & Adjustment Guide  (Read 25135 times)

NightWolve

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I recently acquired 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.  :clap: :clap: :clap:

OK, I slapped some screencaps together, and the comment section of Steve's video has even more information to tune those 3 CD potentiometers like a pro, although it's "rough" so I'll try to make sense of what you must do.

** Proper CD waveform when tuning a CD laser/player **

https://www.facebook.com/steven.hanely/videos/10201717056086907/

https://s5.postimg.cc/j65ephh2f/3_Pot_PCECDOscilloscope-01.png
https://s5.postimg.cc/i3v86y5yv/3_Pot_PCECDOscilloscope-02.png
https://s5.postimg.cc/anvyl6d4n/3_Pot_PCECDOscilloscope-03.png
https://s5.postimg.cc/3xfhbqxon/3_Pot_PCECDOscilloscope-04.png

* You hook the oscilloscope to P5 pins 1 and 2 (1 is ground, 2 is RF signal).

* Pots VR101, VR102, VR103, VR104 each effect the signal differently

* Once you play with it for a min, you should get a feel for it.

* The signal is comprised of a sign wave with a fixed slope and varied amplitude.

* So when the pulse is taller the frequency is lower, the peak/frequency variances are in fixed steps causing a grid effect.

* Your adjustment goal is max amplitude with minimal line jitter.

* VR105 is your sync hold pot.



Anyway, best I can do at this time, it's a real tough job to translate "steve-speak" for the common man (But I try on rare occasion like this YPbPr Component Guide we worked on together).

So, in a nutshell, you must get the CD waveform to look like [this] what it does towards the end of his video while adjusting the pots. Since you say a new laser was installed and the installer adjusted those 3 pots away from factory defaults, it definitely needs to be done right, and this may help you if you solve the spinning problem first.

Personally, I think using a slow-burned CD-R of a game may/might be a smart strategy, you get it fine-tuned with a CD-R and they'll all work which should -- in theory -- guarantee that the laser works with original factory-pressed silvers. Although you may need to test that in practice.

On the other hand, if you only have originals, don't play burned CD-Rs for fan translations or downloads, then maybe don't bother on such an idea - stick with an original factory-pressed CD for tuning.

Good luck!
« Last Edit: May 04, 2018, 10:12:52 AM by NightWolve »

Cordelay

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Oh man! Thanks a lot! I'll check it out when I come home from work, but this looks super detailed and useful.

What scope did you end up getting? I've seen a cheap 2channel 2MHz standalone.


Thanks a lot for taking the time to gather all the info.

NightWolve

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What scope did you end up getting? I've seen a cheap 2channel 2MHz standalone.

Thanks a lot for taking the time to gather all the info.

Me ? I own the SainSmart DDS-140 USB Digital 40 Mhz Oscilloscope, bought it many years ago on eBay for $80-$90 USD. Together with a 7" Windows tablet for another $30 USD ('Twas a "Black Friday deal" via a local brick'n'mortar retailer), it becomes a full portable oscilloscope. The interface software was developed in MSVC++ for Microsoft Windows, so yeah, you need a Windows PC, tablet or laptop, etc. to use it.

https://www.sainsmart.com/.../dds140-pc-based-usb-oscilloscope-40mhz-bandwidth-200ms-s-black



Quote
Thanks a lot for taking the time to gather all the info.

Sure! But didn't you say the CD doesn't even spin ? You got other problems to deal with before even thinking about this I think ??
« Last Edit: May 06, 2018, 08:05:34 AM by NightWolve »

Cordelay

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Sure! But didn't you say the CD doesn't even spin ? You got other problems to deal with before even thinking about this I think ??

Yup, it wasn't spinning at first, but it was troubling me and had spare time on the weekend so I decided to give the first page tutorial a go.

As a starting point I used the xls file where a forum user wrote his ohms readings on the pots of a working Turbo Duo, and then I started tweaking using BlueRaven's and BlueBMW indications on the first page of this post. I got it working to the point that some original music cd's worked (minus some slow loading and a bit of trouble reading con the outer tracks) and the five or six burned games I tried worked alright. I knew it wasn't a permanent fix, but I was able to play games.  :dance:

But yesterday I tried to hook up a small 2MHz portable oscilloscope to try adjusting the pots using your tutorial indications and couldn't get a proper waveform so I assembled again the console and called it quits. I don't know what I touched, but the thing is that now it has problems reading cd's again, so I guess I'll reset the pots to the starting point and and try to get it at least reading burned cd's.

I think the moral of the story is: "You need proper tools and knowledge to do a good job" or also "If it's working don't fix it!"  :lol:

Here are some pics during the process:

https://i.imgur.com/Pxy6LMx.jpg
https://i.imgur.com/gK9LDWD.jpg
« Last Edit: May 08, 2018, 12:13:48 AM by Cordelay »

soop

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this is really good stuff.  I might have to consider an oscilloscope.  I've seen Ben Heck use one to great effect, but it was always a bit mystifying to me, I'll have to watch a tutorial and see if I can work out what's going on (the sheer amount of buttons and dials is a little overwhelming)

Cordelay

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Ok, I've reset all pots back to "average" values, also tweaked a little bit the white laser pot (counterclockwise an 8th of a spin) and the screeching noises have disappeared and works again, music cds read super fast, but burned cds take a little more time.
I think the laser pot might have been adjusted too strong (due to failing caps) and with the new caps maybe it needed to be set back a bit...
As long as it loads games it's fine by me...

Cordelay

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this is really good stuff.  I might have to consider an oscilloscope.  I've seen Ben Heck use one to great effect, but it was always a bit mystifying to me, I'll have to watch a tutorial and see if I can work out what's going on (the sheer amount of buttons and dials is a little overwhelming)

I've been watching reviews of the Hantek DSO5000 series and they seem to be a nice value for the money, but I find it difficult to justify forking down 250 for something I still don't know either how to use or what to use it for... Just a couple months to my bday, so I might get one anyway :lol:

soop

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this is really good stuff.  I might have to consider an oscilloscope.  I've seen Ben Heck use one to great effect, but it was always a bit mystifying to me, I'll have to watch a tutorial and see if I can work out what's going on (the sheer amount of buttons and dials is a little overwhelming)

I've been watching reviews of the Hantek DSO5000 series and they seem to be a nice value for the money, but I find it difficult to justify forking down 250 for something I still don't know either how to use or what to use it for... Just a couple months to my bday, so I might get one anyway :lol:

Yeah that seems too much.  Check ebay for a second hand one, I just looked and there are some old ones going for like 30

game freak99

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Re: REPAIR GUIDE - TurboDuo/PC Engine Duo/R/RX: Laser Swap & Adjustment Guide
« Reply #233 on: November 16, 2022, 08:13:40 AM »
Is it possible or advisable to swap the whole laser assembly between a duo and a duo R?

Keith Courage

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Re: REPAIR GUIDE - TurboDuo/PC Engine Duo/R/RX: Laser Swap & Adjustment Guide
« Reply #234 on: November 17, 2022, 01:19:19 AM »
You can do it if you want. All parts are the same. There's no real benefit to doing so unless you are changing parts because one set is faulty.

game freak99

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Re: REPAIR GUIDE - TurboDuo/PC Engine Duo/R/RX: Laser Swap & Adjustment Guide
« Reply #235 on: November 17, 2022, 08:22:56 AM »
Right now I've got a turbo duo with some sort of sound issue I'm not sure I'm equipped to fix and there's someone locally selling a duo R with a bad disc drive. Between the two of them there's a complete working unit!

Keith Courage

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Re: REPAIR GUIDE - TurboDuo/PC Engine Duo/R/RX: Laser Swap & Adjustment Guide
« Reply #236 on: November 18, 2022, 04:07:54 PM »
If you give up on the duo let me know. I actively do repairs and mods on these systems. So I'd be happy to fix it for you for a small fee.

game freak99

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Re: REPAIR GUIDE - TurboDuo/PC Engine Duo/R/RX: Laser Swap & Adjustment Guide
« Reply #237 on: November 30, 2022, 11:26:38 PM »
So, I swapped the lasers between the duo and duo R, and the Duo R will read audio CDs but not games. Anyone familiar with that issue?

Looking at it, it looks like a previous owner snapped off the pegs the drive sits on and glued them back on, rubber footies and all. Would that make the drive unstable enough to read CDs but not games?

Looking more closely, it would only play the first few tracks of the audio cd (1-10 out of 51) I tried adjusting vr105 and I managed to get it to read up to track 17, but being the author of my own misery, upon a tiny bit more adjustment it will no longer recognize the disk at all even adjusting it back to its original position. I'm confused.
« Last Edit: December 01, 2022, 12:28:09 AM by game freak99 »

game freak99

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Re: REPAIR GUIDE - TurboDuo/PC Engine Duo/R/RX: Laser Swap & Adjustment Guide
« Reply #238 on: December 06, 2022, 06:09:07 PM »
If you give up on the duo let me know. I actively do repairs and mods on these systems. So I'd be happy to fix it for you for a small fee.
I'm looking at that duo board and I'm basically convinced that Q304 is toast. it's getting 12.1V from the regulator and 8.9 V on the other leg, but is only sending 1.65 Volts out. Can I jump it to get 8V out into the audio corner of the board?

TorqueEmPup

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Re: REPAIR GUIDE - TurboDuo/PC Engine Duo/R/RX: Laser Swap & Adjustment Guide
« Reply #239 on: August 17, 2023, 02:29:13 AM »
Recently just acquired a Duo-R, it was known to have disc drive issues, but working HuCard slot.
I figured that at worst, I get a working PC-Engine that just can't play CDs.

Well when I first tested it today after Fedex delivered it, I popped in a pressed music CD, and after hitting Run the CD drive just revved up slowly but steadily up to an extremely fast speed. It never would stop spinning and would endlessly say "Just a Moment..." Opening the lid the disc wouldn't stop spinning either. It wouldn't stop until the system was reset or power cycled.

So I cracked it open, and was pleasantly surprised to find it had been recapped and the board was extremely clean, almost as if it was brand new. Even had the Super Capacitor for the Backup Memory replaced with a 1f supercap.

After fiddling with it for a little while I found the laser sled motor would not return the laser to the center. I later found testing the resistance of the motor, and it was completely open unlike the working motor in my other parts Duo.

So I swapped the entire optical drive assembly from the parts Duo, now the disc drive is behaving more normal. But no discs can be read at all.
It moves the laser to center, and the lens bobs up and down, and the laser diode is illuminated. (Very brightly if I use my Cell phone camera)

Looks like someone else in the past already tried tweaking the pots as they already had marker marking their original positions.
But I attempted some pot adjustments to see if the laser will finally see the disc. No dice. I checked all the values and compared them with values found in this thread, and all seemed normal.

I looked up and down the board around the CD ICs, looking for any bad vias, or traces, or even bad solder joints and making sure all the caps were in the correct polarity.
Everything looks perfect.

I tested the cables for continuity, all passed.

I tried both lasers in the assembly with the good sled motor, both exactly the same response. Return to center, lens bob, diode illuminates brightly, disc nudged a bit by spindle motor once, then it sits for about 10seconds while the laser diode is still illuminated the lens bobs up and down slowly trying to focus the laser, the spindle motor nudges the disc again and then it quits, with the message on screen telling me to "Please Set Disc"

I ordered a new laser, but I am not confident it is going to fix anything. As I've read through this entire thread and found a couple people with the same issue that seemingly never could figure out what was wrong even after installing a new laser.

I read something about some mirror in the laser assembly, and the CXA1081. Chip seems to be working fine but I don't have a scope and have no intentions of ever getting one, so I can't be 100%.
while the system was on, I tried looking for chips that were getting hot. Nothing.

I tried reflowing a couple drive chips, namely the CXA1081, and this didn't provide any change at all in how the drive was attempting to read the disc.

Any help would greatly be appreciated.