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

[robotype]

it could be cap related
there is a mixer circuit that uses cap charge to adjust the mix levels

I want to recap that section, can you point me at which caps could be related to the issue?

[MNKyDeth]

I will go out on limb here and suggest robotype that if you do open up the Duo you should do a full cap replacement on the system. It will only get worse over time if you don't.

Of all the research I have done on the subject from threads on these forums it is in you're best interest to replace all caps on any Duo's if they have not been replaced already. I am not a guru here so second opinions are welcome. I recently did my own Duo and it's like a new machine again.

[robotype]

I opened the duo many times it's very quick I want to try and replace only the caps related to the audio mixing section before the full recap (which I will certanly do when I get the full cap kit)

[BlueBMW]

You're wasting your time only doing a few caps at a time.  There aren't that many total, just do them all, wash the board good (dishwasher does the trick) and enjoy the duo for years to come.

[robotype]

I promise you I will do the full recap but just out of curiosity, if someone knows it, which are the caps related to the audio mix?

[thesteve]

The 2 SMD caps behind the heatsink on the right
They leak so cleaning the area is as important as the parts

[robotype]

The 2 SMD caps behind the heatsink on the right
They leak so cleaning the area is as important as the parts

great! thanks

[robotype]

ok I replaced the two smd behind the heatsink on the right and didn't help, so I replaced the two in front but nothing changed so I recapped the whole thing and now I hear sound effects loud and clear. I think the two caps related to the mixing are the two on the right (near the cd player).

my duo now plays anything perfect (only original games, I don't have CD-Rs)

these are my impedance readings

101 AB  7.3  AC 13.4  BC 19.1
102 AB  8.6  AC  7.8   BC  9.9
103 AB 15.9 AC  2.5   BC 17.8
104 AB 19.4 AC  1.7   BC 20.3
105 AB 0.00 AC  0.36 BC 0.36

I didn't measure the white pot on the lens

[danyetman]

wash the board good (dishwasher does the trick)

*throws hands up in exasperation*  Why on God's green earth does everyone give this horrible piece of advice?  This is probably one of the worst things you could do!  Dishwashing detergents are overwhelming alkaline in nature, which will cause corrosion on metallic surfaces on an epic scale if even the slightest bit remains.

In addition, some of the more aggressive dishwashers are fully capable of pulling SMT components off of boards.

If you want to clean a board properly, use non-alkali degreaser, a soft/medium toothbrush, and do it by hand in the sink.  Then spray the thing down with 90% Isopropyl alcohol and let it air-dry over the course of 3-5 days in low humidity.

[BlueBMW]

I have washed dozens if not hundreds of boards this way and all are still in great operation today.  I work in a circuit board manufacturing plant and guess what we basically use to wash our boards, industrial dishwashers with very similar detergents to what you use at home.  Use very little detergent and you dry the board with an oven.   What I do at home is essentially the same as what I do at work.  And the stuff I build at work goes into satellites, spaceships and weapons.

Scrubbing by hand is great until you miss leaked electrolytic fluid under a chip or in a via that you cant get out with simple scrubbing with a toothbrush.  I know. I used to do it that way... 99% isopropyl and a toothbrush.  Even after that some boards would still have issues.  After a dishwasher wash and oven dry they work perfectly.

Is there some risk with washing them in a dishwasher?  Of course, but I think the risk is far less than leaving leaked electrolytic fluid stuck in some vias or under chips causing a slow death of the traces it touches.

You know who I learned this technique from?  None other than thesteve whom you praise in your signature.

[BlueBMW]

Here's a pic for posterity...

X68000 Compact Mainboard going in for a wash   Computer came out great and works awesome still to this day.

[Necromancer]

*throws hands up in exasperation*

Throw your hands in the air like you just don't care..... because nobody here cares what you think. 

[ProfessorProfessorson]

wash the board good (dishwasher does the trick)

*throws hands up in exasperation*  Why on God's green earth does everyone give this horrible piece of advice?  This is probably one of the worst things you could do!  Dishwashing detergents are overwhelming alkaline in nature, which will cause corrosion on metallic surfaces on an epic scale if even the slightest bit remains.

In addition, some of the more aggressive dishwashers are fully capable of pulling SMT components off of boards.

If you want to clean a board properly, use non-alkali degreaser, a soft/medium toothbrush, and do it by hand in the sink.  Then spray the thing down with 90% Isopropyl alcohol and let it air-dry over the course of 3-5 days in low humidity.

I think you have no idea how the f*ck this has been common practice in the professional electronic repair field for years now for both arcade vendors and computer repair shops. Also, why would you just spray alcohol  all over a pcb and let it sit. What magical process do you think the alcohol does on its own with no human interaction as it dries?

[danyetman]

The alcohol, Mr. Attitude, is used to assist evaporation of the water in order to assure that there's no water left in or on components when it's next powered up.

And for the record, 'common practice' /= 'good practice'.  It is 'common practice' (or was in the 80s and 90s, at least) to blow on NES cartridges when they didn't make a good connection.  However, we know now that this was a placebo fix, and in fact assisted in corrosion of the cartridge pins thanks to the moisture of the blower's mouth. 

Now tell me something - is it 'common practice' to get pissed off and start swearing at someone when you clearly didn't read the entirety of my post?  I quote from my immediately previous post:

If you want to clean a board properly, use non-alkali degreaser, a soft/medium toothbrush, and do it by hand in the sink. Then spray the thing down with 90% Isopropyl alcohol and let it air-dry over the course of 3-5 days in low humidity.

Yet all you focus on is the alcohol, to the exclusion of all else.  In fact, you take that single statement completely out-of-context and treat it as if I prescribed that as the sole remedy, completely missing everything leading up to that.

Next time you want to get pissy about something, do yourself a favor and make sure you know what the hell you're responding to, genius.

[ProfessorProfessorson]

You don't need alcohol to dilute water to assist in drying. All you need is patience, warmth, a small enclosed space you can prop the boards upright in, and a fan. Its called making a drying station. Stop being a lazy f*ck trying to act like a know it all pro. You can save the alcohol for actual spot cleaning moron. All you are doing is....lol pouring money down a drain, figuratively speaking.

As for washing boards, its been done in factories and in small repair shops for years now. You have the option to use a cleaning agent or not. Usually just an extended and thorough powerful wash of warm water will do the trick in many cases. You acting horrified at the fact we do this is laughable. It shows how clueless you have been to how this stuff is done on a professional level since jump street.

Scrubbing by hand does not get into nooks and crannies and expose trace damage the way a good wash will. I have done game system, arcade, computer pcbs, and pc power supplies this way for years now with no issue. I have yet to see anything damaged by a wash. No components ever broken off or damaged. What I have done is spot old damage after said wash so I can repair it while avoiding wasting hours of my time trying to pick out bits of crud and corrosive material I missed from a tooth brush scrub.

I'm sorry you don't get that. But hey, just keep your methods to yourself, and shut up when grown folks be talking. Don't like the "attitude"? Fine, leave then. We dont suffer fools around here.


Side note, since we are on the topic of cleaning pcbs, because there is actually dumb f*cks out there that do this, for god's sake don't clean them off with shit like WD40. I have seen the damage that kind of shit does. It isn't pretty.