Blog of my Turbo Duo repair

[JoeQuaker]

I took some time to write up some notes and things I learned along the way while I did a recap job on my Turbo Duo.

http://jizaboz.blogspot.com/2018/07/nec-turbo-duo-repair.html


Please feel free to critique or humiliate! I'll update the post with anything you all think is important to add or is just plain wrong.

[Keith Courage]

As far as your CD drive is concerned. Does it spin up really fast starting slow at first or does it just spin one speed not changing at all?

[JoeQuaker]

I would need to check again to be sure but I think it's the latter. The last time I tested it in between a few batches of caps it would try to load my Bonk/Gates of Thunder CD but had seek probs and audio was skipping all over on that and audio CDs.

[Keith Courage]

Oh, well if it is partially working with audio CDs then that is a good thing. Don't forget to clean off the lens itself with a Q-tip. If that doesn't fix it then probably just needs the lens rails cleaned and re-greased+lens potentiometer adjustment.  Usually V102 is the one to try adjusting first. Try turning it to the left slightly.

[JoeQuaker]

Ok Keith, I did another test today after playing some card games.

I was actually hearing skipping auto and barely loading the bonk/Gates of Thunder disk before I replaced all the capacitors just to clarify things. It was still skipping around a Van Halen audio disk and trying to load games at the time I had about half the caps replaced. I did not have the caps nearest to the CD-ROM replaced yet at that point.

Now that the re-cap job is done, I don't even get skipping audio. However, the disk doesn't just spin continuously. At one point testing tonight I opened the tray and the bonk/GOT disk was completely stopped as well as seeing the CD-ROM LED kick off and on occasionally. Listening to the mech of the drive, I hear that "sik sik sik sik" sound at intervals as if the laser is seeking.. but I never hear that familiar groaning "errrrrr" sound that the drive used to make as it loaded a game. I've cleaned the lens again too btw.

I haven't adjusted any pots yet but wanted to go ahead and share this with you in case it gives you any clues. I also have an oscilloscope if you can tell me what/where to measure. I saw an old thread talking about this but some details are still vague to me.

[Keith Courage]

Hmm well I can't think of what could have happened during the cap change that could have made things worse other then a connection not being good somewhere.

I'd start by turning the V102 pot slightly to the left and see what happens. I tune all my lenses by ear so I can't give you any values to get fore the lens adjustments unfortunately. I do this because I find that not all lenses work good with the same settings as others.

[JoeQuaker]

Today I wanted to clean the case so I thought I'd look into this again. Checking my work again near the CDrom area, I saw 2 of the last caps I installed had loose legs  Yeah, surface mount soldering isn't exactly my best skill heh. So, I fixed that and got them nice and snug, then removed the magnetic hub from the case so that I could test a CD with everything open. I posted a video of that test here:

If you turn up the volume, you can hear the sounds of the drive.

I haven't touched any pots yet but I did go ahead and mark their current positions with a sharpie for later. Wanted to go ahead and show you this vid before I proceeded. It's not exactly an emergency anyway because I don't have many CD games to play at the moment.

Edit: And upon inspecting again I see on leg on c507 is loose. (jeez). c201 and c200 were the ones with loose legs earlier.

Edit: Leg of c507 fixed. Tried turning V102 a bit to the left but didn't see any positive change. Put pot back at original position for now. Something really still nagging me is I don't think the lens ever moves to the outside of the disk! Like previously mentioned, I used to recall a "groaning" sound the drive would make that isn't present anymore.. I think that occurred when the lens moved all the way to the outside of the disk. Perhaps my gears are bound up some how? I have yet to apply new silicone grease to them.

[NightWolve]

I posted a video of that test here:

If you turn up the volume, you can hear the sounds of the drive.

Fraken Duo, it's alive!! ;)

[JoeQuaker]

Tinkered with this some more today. Made sure all caps on my first few batches were before I had better surface-mount soldering practice ;) Not seeing any more "floating legs" or anything crucial like a backwards cap.

Messing with the v102 pot again I've got nothing but a spinning audio disk. I slight adjusted pot v103 as well but I can only get the laser to behave differently rather than better. For instance I figured out a position of those 2 pots that would make the laser stay in one place longer before reading. (of course I marked the original northern position of the pots)

I haven't messed with the other pots yet. For all I know the laser is finally dead. This thing did load a lot of CD-Rs about 17 years ago  It did work a few years ago but just barely with a real game CD (random failed load on real 4-1 with Gates of Thunder hanging and/or audio skipping, random fail to load on Sherlock Holmes then locking up seconds into an FMV on a CD-R, real audio CDs skipping all over) before I started the cap process and I want to say about 2 batches into my repair blog.

Other notes I may should mention is I have not completely removed the PCB (only raised slightly and shined a flashlight in to look for leaky cap evidence) as I didn't want to replace anything but the surface-mounted caps yet at this stage. That should eliminate the chance of ripping ground wires off the bottom.. hopefully? I also have not replaced any cap in the original power supply yet.

Part of me says something I did in the re-cap phase messed something up as the CD-ROM used to read discs barely.. but another part of me says perhaps with proper voltage my worn-out laser is just failing for some odd reason. Totally open to any more ideas and opinions. Should I go about just trying to replace the laser? Try to adjust more? I can't get this thing to even start reading the data it seems despite all the spinning.

[Keith Courage]

How well does it read audio discs? Does it seem to have trouble when skipping from track to track?

[JoeQuaker]

How well does it read audio discs? Does it seem to have trouble when skipping from track to track?

That's actually what I'm testing with. I've got an old Van Halen disc with no scratches I'm trying. I also tried with the 4-1 disc. It's like it just isn't reading the disc despite it spinning and the laser moving. It never even begins to play.

[Keith Courage]

This can be the sign of bad traces/shorted out vias near capacitors somewhere in the CD drive function area of the board. I would start by holding the board up to a light and see if you can see through all the Vias for capacitors found below where the CD drive sits. IF there is black gunk in there you might need to repair using a wire or spare cap contact lead.

If that isn't the problem then I'd try another CD lens if you have one.

If that doesn't work then unfortunately this symptom can also be the sign of a bad chip on the board. So you might need to send this to thesteve for chip replacement.

[JoeQuaker]

Just a quick followup..

This has been sent off to TheSteve. Besides hitting a wall with getting the CD-ROM working, it would give me peace of mind to have someone with a lot more experience than me working on these things to take a 2nd look at my work to confirm what I did is right or if I missed something.

[thesteve]

Final diagnosis
this was entirely solder and prep issues
several caps were not soldered down on both sides
some of the old cap legs hadnt been removed from the pads, and the solder hadnt been heated enough to flow
the 3.3uf cap was overlooked
the new cap legs were excessively long and some were touching other traces
removed all caps and reinstalled completing the cap change, unit started right up loading fine with some audio drops
slight adjustment with scope and its running well

[thesteve]

im sure your iron was a big part of the issue
i used a 40W temp controlled one @700F
liquid flux helps allot as well
simple rule (less is more) you want the solder to be smooth and follow the surface of what your soldering
any lumpyness to the solder indicates low temp or contamination and should be cleaned and redone

[JoeQuaker]

Haha I figured as much! I didn't exactly have a lot of faith in my work. I've done a lot of soldering but that's the first time I've attempted surface-mounted.

I was using a 15 watt iron with no temp control and I've never used liquid flux!

Thanks again for diagnosing this and I will include your notes in my blog for reference.

[NightWolve]

Another successful Le-Steve-to-the-Rescue story!

I do like seeing DIY initiative, Jiza, thought you'd be alright when you started out, hoped for the best, but oh well, doesn't hurt to admit/recognize when an experienced professional touch is needed to be called upon.

I still haven't recapped my Turbo Duo because I wanna record a DIY video along with building the YPbPr/Component circuit live, but I procrastinated on planning it, life got in the way as well, so the further I got from those plans like 4 years ago, the further my interest waned, heh. I was successful with my Turbo Express, at least, which was broken and needed a recap immediately ('twas thanks to the help of PCEFX many years ago).

Producing respectable videos for YouTube that won't embarrass you later just takes a certain kind of talent/patience/charisma/motivation that I don't have I found, so I really respect personalities like Game Sack and "Lord" Voultar (heh, I like this guy, & he's registered here on PCEFX).

[JoeQuaker]

Oh that's cool.. I forgot you even had a Turbo Express that didn't get stolen like mine did!

Not only does it sound like Steve got me fixed up proper, but knowing exactly what I did wrong is also great to know. It's silly to be shameful of these things considering the learning curve. I think this scenario worked out OK. Big mistakes I made was not removing every bit of old solder even though I knew I should be  (I was TERRIFIED I'd lift one of those little pads), not using a hot enough iron (didn't want to burn something!), pretty crappy tools (even my smallest tip felt too big and I was leaving the cap legs too long just so that I could install them without burning my fingers) and ultimately not having nearly enough experience with this sort of work. Should have found a cheap, crap PCB with surface mounted caps to practice on first.

Working on things like Wells Gardner arcade monitor chassis I've always been keen on using at least a 30 watt iron and removing every bit of old solder. When it comes to parts like the flyback transformer you have to get all that crud off anyway or you aren't getting the old flyback out without breaking something haha. Working with that stuff though in no way came near the "Oh god don't ruin it!" paranoia that came with working on this little Turbo Duo PCB. Stuff is just much bigger and looks less fragile too on something like a monitor chassis PCB or even a Famicom PCB. I've got 2 spare K7000 chassis laying around.. I do not have 3 Turbo Duos in my house heh. So, I did a janky job of doing things like just cleaning old solder on a pad with a big of old leg still in it with alcohol, adding new solder to stick to that, and sinking the cap legs into it (which of course is wrong. Even if it sticks the connection is weak at best).

Best case scenario is that I helped things by getting all those old caps off about 2 years ago before any more corrosive stuff leaked out. Worst case would have been lifting multiple pads and burning up traces being aggressive with it.

I'm going to add notes like these and what Steve has told me to that blog. One of my pet peeves is when someone puts instructions or guides out on the internet, it's discovered that part or all of it is wrong, and the author refusing to admit their mistakes! Thanks again to The STEVE!

[thesteve]

honestly your blog seemed about right (didnt really promote the mistakes)
as for the old solder, it doesnt all have to come off as long as its clean (a touch of flux restores it as long as its not soaked in cap fluid), but the old cap leads must
the fluid corrodes under the solder sometimes so the pads dont bond anymore, removing the old legs exposes that
solder should always cover the pad thin, because a thick blob can mask poor adhesion

The way i do it is I prep the pads with a puddle of solder on them, then add a drop of flux to the top
next i hold the cap in place and reflow the solder melting the cap leg into it
the flux on the pad preps the surface of the wire and helps the solder bond to it

[Amerika]

I know using pliers and twisting is a workable solution to pulling electrolytic SMD caps.  But in my eyes that is like taking a jackhammer to a artifact dig site.  Sure, it might be great in some cases...except when it is not (like when pads have been soaking in electrolytic fluid for years and weak).

Air stations are not super expensive and you might even know somebody who has one.  I bought one of these guys and even though it's not a commercial grade product, it works extremely well for my purposes - https://www.amazon.com/gp/product/B00P8Z4RPG/ref=oh_aui_search_detailpage?ie=UTF8&psc=1.  And it's much cheaper by itself than destroying any of these old systems or paying to have one repaired after you've destroyed it.  Besides being safer for the board, it's also insanely easier, faster and more versatile for doing repair work as there is some cases where it also helps with installs (especially when combined with kapton tape).  Hell, you might even be able to rent an air station for cheap from some places.

And using an iron to remove SMD caps also isn't too rough if you know to add more solder/flux first so you have more area to spread the heat to and get all of the solder holding the leg to flow.  This is a common mistake that I've seen made and made myself before I knew better.  More solder/flux is almost always the answer when removing anything and not more heat.  And the irons tip can also make the difference.  If you're using a pen tip you have very little surface area for heat to spread to the solder so in some cases you might need to put the iron sideways touching the solder.  Or you can get a different tip that looks like a chisel end for situations like that.

And what Steve said above is most definitely the best way to go about installing those caps.  In cases where there was almost no room to work (and to avoid melting plastic), I've kapton taped off the surrounding area, put solder on pads and then used the air station to heat the solder.  Then place the cap (or more recently inductor coils) as the solder pool stays molten for long enough to place what you need (I use tooth picks to hold things down usually while the solder pool cools).

[JoeQuaker]

Thanks for the extra advice guys.

Well it arrived today.. a few days earlier than expected. Plugged it up, popped in Y's III disk and BOOM worked instantly. I've been playing for about an hour.

Thanks for the great work, thesteve! 

[thesteve]

air stations are great for some applications, but risky for others
some of the plastic parts melt way too quick and these old caps will burst before the solder melts

[Amerika]

air stations are great for some applications, but risky for others
some of the plastic parts melt way too quick and these old caps will burst before the solder melts

That's what kapton tape and using extremely controlled air flow and proper technique is for.  Kapton works wonders on plastic and anything sensitive.  I've been able to pull components that are within 2mm of plastic with some well placed kapton as I've worked on a lot of handhelds lately.  It's way better than melting the plastic with your iron tip in those situations as even a pencil tip will get the area too hot for too long and less risky than twisting IMO.  Now if you have other heat sensitive components then you better know what you're doing to pull them.  So, of course, be careful in your usage.  In those cases it might be better to use the twisting method.

I've yet to have a cap vent on me using hot air.  However, my sample size is small as I've only pulled a few hundred at this point and not thousands like yourself or others.  I also wear eye/face protection no matter what tool I'm using so it's kind of a non-issue anyway.