PC Engine Duo - White Screen/Multi-Colored Screen

[Zer0-2k11]

Hi Everybody,

I'm having a bit of an issue here with the PC Engine Duo listed as no power off eBay last week. When I got it, it was mostly recapped by the previous owner (Horrible job).

Before turning it on, I opened it up and checked for any Vcc and GND shorts, but it was fine. 

Grab my only PC engine HuCard (Street Fighter II), slided it in, turned it on and behold white screen. Turned it on and off a few times and I'm also getting purple and yellow colored screens along with multi-colored screen that moves (I hooked up the duo to my capture card). So I thought let me check the CD portion. Took out the hucard, turned it on. Same thing, white screen .

Since the caps were no name or an unknown brand, I swapped them out with a Console5 SMD cap kit and still same thing.

I also tried out other things, but still nothing (Not in order).
Reflowed 6260
Replaced 6270
Replaced 6280
Replaced Video Ram
Replaced Work Ram
Checked HuCard connector for shorts
Replaced logic IC's except IC517 (2 were running very hot - almost enough to burn your finger but replaced all except IC517).

Spent about 3 days straight working on it and for the life of me can't figure this one out . Anybody have any ideas?. Any help is greatly appreciated.




*Edit* Checked all traces of 6270 using the netlist and had 2 bad traces, but symptom's are still there: http://gamesx.com/wiki/doku.php?id=hu6270_netlist

*Edit2* Checked all traces of 6260 using the netlist and had 1 bad trace, but symptom's are still there: http://gamesx.com/wiki/doku.php?id=hu6260_netlist

*Edit3* Checked all traces of 6280 using the netlist and had 2 bad traces, but symptom's are still there: http://gamesx.com/wiki/doku.php?id=hu6280_netlist .

*Edit4* I whipped out the oscilloscope and found that the 6260 is only getting 60hz? (Sounds like it's for NTSC video, but Netlist homepage shows it should be getting 21mhz?. The 6280 is getting 21mhz though).

[wookieb81]

I have the same issue. Just got one today and hucard side and cd side both give me solid white screen, tan screen, and green screen 

[thesteve]

you have logic running hot, start with 5V voltage checks
then replace anything hot
also what is your supply output?

[wookieb81]

Turns out it was the AV port. Good luck on yours!

[Zer0-2k11]

Thanks wookie.

Thank you thesteve for helping me.

On my AC adapter I'm getting 17v

I checked out almost all IC's:

The Logic Chips (IC516 to IC520) = 5V
Hu6260 = 5.010V
Hu6270 = 5.009V
Hu6280 = 5.010V
Ram Chips (HSMR series) = 5v
IC106 = 5v
IC501 = 5v
IC505 (Pin 1) = 7.77v
IC505 (Pin 14) = 3.243v
IC512 = 5V

I tested some of the caps that are connected to rails and I noticed C961 is getting 4.1v on it's positive side. Is that normal?.

[thesteve]

that sounds right
so you have some chips running hot, which ones?

[Zer0-2k11]

The ones that were running hot were IC516 and IC518, but I also replaced 519 to be sure (Didn't have enough logic chips to replace IC517, but it wasn't burning hot). The replacements look like they are back to running warmish again.

[thesteve]

Ic520 is the only common failure
Cards work with it removed

Sent from my VS920 4G using Tapatalk

[Zer0-2k11]

Shoot. I seen your post too about removing IC520. I removed it and still same results. I got a logic probe coming in to see your advice on checking to see if the hucard pulls high, low and all that just in case I missed something  . It should be here next week sometime.