Turbo Duo quick white flicker then nothing when powering up

[crispytreat]

Hi All,
I have a PC Engine Duo that I have replaced the caps on.  When I power on the unit I get a quick white line that flickers on the screen for a brief second and then nothing.  This is the same with or without a hucard in the unit.  Before the cap replacement the hucard side would work but the CD side would not spin up.  I have another working Duo so I have been doing some side by side comparisons checking voltage and continuity but I am stuck.  The only thing I notice is that C610 is only showing 1.6 volts on the bad unit but 3.8 volts on the good unit.  I don't know if this is related to the fact that the unit will not power on.  I suspect it may be a short but I am not sure how to track it down.  If I put my TED in the system and power on the system the led on the TED will flash for a second and the screen will flash then it goes dark again. 

I am just seeking guidance on next steps to help me diagnose the issue.

Thanks in advance.

[bozo55]

I would use a loop or magnifying glass to look over the entire board for solder bridges, cold solder joints or solder splashes.  Barring any of that I would very carefully and patiently re-flux and re-flow every solder joint you made with a nice thin screwdriver tip and low wattage iron.

[crispytreat]

Thanks for the feedback.  Here is the latest.  I spent a day checking vias and solder points.  Out of frustration I decided to reflow the ics on the board one at time to see if that made a difference.  Once I got to HU6260 and heated it up with the hot air tool I was able to get the system to boot up.  It was very fuzzy but I was able to see enough to start up a game.  I then removed the chip completely cleaned up the board and resoldered it with the same result.  So I assume the chip is bad.  I then swapped out the chip from a working duo and everything booted right up.  At first I thought it was fine but the colors looked off.  I booted up 240p test suite and the blue is so dark it is barely visible.  The red, green, and white look ok.

I am not sure if I messed up something with the 6260 when moving the chip.  I have checked the composite signal at multiple spots on the board and it is the same, very dark blue.  I am thinking about ordering a new 6260 from http://gamedoctorhk.com unless there is something else that I should try.

I removed IC520 before I started to isolate the PC engine side.  Once I restored that I am now working on the cd side.  I had issues with the disk spinning but I noticed if I put pressure on the Sony chip in the bottom right corner below the cd drive the drive would start spinning.  I cleaned up the chip some and reflowed a few of the pins but now when I start up the duo the disk just starts spinning it does not matter if I push run on the controller or not.  Next I will remove the chip and clean it up and see if that makes a difference.

So the current status is I replaced the Hu6260 now video works but the blue is super dark (Maybe the overall picture is darker).  Also the CD rom spins on its own when powering on the duo.

Any other advice or recommendations are greatly appreciate and I will provide an update once I make more progress.

Thanks

[crazydean]

I enjoy tinkering and making this work, but this is well beyond what I would do. I commend your diligence.

[crispytreat]

Here is the latest. I have ordered a couple HU6260's from http://gamedoctorhk.com I have no idea when they will get here.

I swapped 6260's to confirm that I have one good one and one bad one.

Until then I am restoring my previously working duo.  The first thing I noticed is that when I put the 6260 back on the working duo the picture was fine.  The issue I had with the dark/missing blue is fixed and no longer a issue. I am still not clear if the issue is that the overall picture is dark or just the blue is screwed up.

Also while the good 6260 was on the non-working duo I had the issue where the CD rom would spin up no matter what as soon as power was applied to the system.  I checked all vias and everything looked good. So I am not sure what the issue is.

I swapped out IC102 and confirmed that the bad duo had a bad IC102 and putting the good IC102 on the bad duo did not resolve the problem.

I cleaned up IC104 by removing it and cleaning up a lot of junk and reapplying the chip.  I did not swap with the working duo.

So to summarize swapping the IC102 and 6260 to the bad duo did not fully fix it.
Should I swap out any other parts to test validate?

2 bad chips on one duo is not a good sign, hopefully there are no others, but we shall see.

[thesteve]

please use the chip numbers not locations alone as i would need to grab a board and locate them to help
the missing color could have been a 6270 problem
the 6260 bad after recap was unlikely, but intermittent vias are common on boards that had leaking caps
the free-running motors is normally an open 5V via by the 2 47uf caps near the controller port

[Keith Courage]

Did you check the traces to the 470UF cap near the power switch? Normally no video is caused by traces getting damaged there during a recap.

[thesteve]

That was my first thought, but he swapped the 6260 and got a pic ruling that out