Duo blank screen help

[Slypty]

I bought this Duo from Japan for an absurdly cheap cost, maybe I should have read the fine print.

  When it arrived it had a yellow or gray or pink screen.  So, I decided to do a complete recap.  After completion, the System still acts the same way, yellow/blue/gray screen only.

  I've checked for bad traces, nothing stands out.  There's a few traces with some leakage but the continuity seems fine.  One thing I did notice, is that caps C614, C613 and C323 only give out .9V of power when powered On.  On my working Duo, these voltages stand out as 2.4V approximately.

  There's an array of resistors underneath these caps, I've taken some pics of the areas in question.  There's also some corrosion by the power input, but I've checked the Voltage Regulators and they emit the proper voltages when On.  Anybody see anything out of whack? 

Anybody want to tackle this fix if I can't?

[Slypty]

Leak near power input

[NightWolve]

I presume you didn't wash the whole motherboard after desoldering all the old leaky capacitors ? That's kind of an important precaution to avoid that fluid causing trouble and future corrosion.

Sounds like it'll be a tough job now to track the problem down and a pro EE will be needed. If you want the best, try messaging "thesteve" - he has full formal training in EE, runs a repair business from home dedicated to console repair/modding, etc.

Before that though, I'd wait a week or so for opinions by others here to see if there's still a chance for you to troubleshoot it yourself before shipping it off.

Do the voltage regulators work properly ? One should read 5 Volts, the other 8 Volts as I recall, and full, unregulated power from the adapter is sent to the CD area. Of course, the Japanese Duo is slightly different so I may be off on that.

I hope one of the ICs didn't go bad on you, then you're screwed unless the repair folks have spare parts... :/

[Xenogears]

Check the VIA around and under the Card-Slot and also trace the ALS244 and HC245 IC. They are the "Bridge" to the BIOS and the "Wall" to the BIOS if a HuCard is insert...

[Keith Courage]

Did the system look like it had already been worked on prior?

[Slypty]

Did the system look like it had already been worked on prior?

No, not really.  The Hu pins are all in tact and no solder on their joints other than original.  I've removed all the acid I could before I did the recap, it can be painstaking when you don't have a professional cleaner.. I just use a brush and some vinegar and finish up with alcohol.

 The flux I use is crap so it looks like acid, it's the same brown color and doesn't come off easy.  Bad choice on my part.  I'll get to the Via's and the ALS244/HC245 chips later today.

  Would it be ridiculous to just swap all IC's with an old crap Duo that I've used for parts over the years?  Seems a bit overboard but might be easier than sending in

[Xenogears]

First check the VIA. In 98 % of all issues, it´s the VIA/connection/Solder Blobs, torn connections/Short...

[NightWolve]

Would it be ridiculous to just swap all IC's with an old crap Duo that I've used for parts over the years?  Seems a bit overboard but might be easier than sending in

Yeah, that's going in blindfolded, playing "Eeny, meeny, miny, moe" with this or that IC, more risk than the slight possibility of reward (you don't know the source ICs from the other Duo are all good!)... I wouldn't, and if you've exhausted other possibilities like failed vias, traces, etc. as mentioned, plus not having the know-how to detect IC-failures, time to just send it off to a pro rather than cause more potential harm...

[Keith Courage]

Lots of times this is caused by a bad chip but it can sometimes be bad trace related. Send it to thesteve for repair. He is the man when it comes to chip replacement and trace repair for them.

[Slypty]

So I checked the Via to the ALS chips as per Xenogears recommendation, thanks by the way it has been a useful tip.

  I'm getting more resistance than I should on most of the Vias from the first 2 left ALS chips to the Hu Card pins, mainly about 12 mOhms... seems unusual.  Also seems to have a lot of old gunk around the Hu pins, need to do a thorough cleaning. 

  Sounds like I have a bad trace somewhere?  Or possibly one of these ALS chips have gone?  Anyways not sure where to look now, might need the ALS pinouts to check for a bad trace underneath.

[Xenogears]

...please buy a Logic Probe. That makes finding Errors a lot easier. So you could check, what happens on the Pins of each IC. A simple broken Adress or Data-Line and you get the blank screen issue.

[Slypty]

Thanks for the advice, I ordered one a few weeks ago and finally arrived.

  I was able to  find a few suspect areas with the probe, but because I can't find a complete schematic I don't know where to start on the board to find a faulty area. 
Basically the fault zones seem to be:
Hu Card Pin 28, varies.. usually no signal from the probe
IC 517 Pin 15, No Count (has a reading of 1Y3 on console5 IC schematic, but I don't know what that means)
On the ROM Chip HuC6260, I have no values on 2, 17, 23, 30 and 37. 
 
  I'd like to know where a schematic is to help me zone in on a trouble area, or if someone has had a similar looking problem anything helps now, thanks

[Slypty]

After checking the Hu Card Schematic, I found out that from Leg 77 on the Hu6280 is supposed to run to Pin 28 on the Hu Card slot.  I checked and there is a short there, so I did a quick wire fix and connected the two points.  It did make a difference:

  The screen comes on differently, it flashes between a jailbar screen and the System 3.0 screen, but the System 3.0 screen is blurry.  When I power down the console, for a brief second the screen looks as it should before it turns Off completely.

  I also noticed that by connecting these points, the Via on IC 517 Pin 15 has been corrected.

  The Hu Card 6260 points still don't seem to be getting proper signals though, the mentioned pins in my last post (2,17,23,30, & 37) are unaffected.

  Does the GPU 6260 run to the 6280 or vice-versa?  Anybody know a schematic to help my find a potential fix?  Thanks

[Slypty]

Lol well after all that seems to just be a missing tiny resistor.  Hu6260 Pin 2 is for the clock, so I just ran connections back from there and found a missing resistor, R137.  I don't have it handy but I think a friend does locally.  Thanks for the help in this one, should end up working.

[NightWolve]

That'll be impressive if you do wind up fixing it yourself! I do recall missing resistors in some other cases though BTW, there are old threads where something like that was noticed.

[Slypty]

Unfortunately the missing resistor did nothing. 
 
  It's on nearly the same path as the Clock's path, the #2 pin on Hu6260 is for the clock, and it's still not giving me any data when using a logic probe. 

 It's possible another resistor shorted around there because it fell off, I don't really know.  Back to the lab, if I had a schematic that shows where the link between leg 2 on 6260 and leg 26 on 6280 might cross paths it's possible there's a short between them.