Pc-Engine DUO - White Screen - No sound, No Boot, No Bios loaded

[Lunacy]

Hi people,

First i would like to say that this forum is a real informations treasure !
Thanks a lot to people who help other people to find solution about PC engine Console. 

Today i have a problem with a Junk Pc Engine DUO i bought.

When i power on it, there is nothing on the TV, only white screen.
Always white screen, with Hucard, Without Hucard. No sound, no CD-rom BIOS..

I checked continuiting points from IC513/IC513 and IC515 with multimeter > Its OK

I replaced some Caps but always same problem. I check Hucard ports and cleaned it with Propylic alcool then looks good... It's seems no burned points on mainboard or under the HuCard port, i checked it.

My questions are :

> What are the first video capacitors to be changed ? Do I have to change them all ?

> What are the first tests I need to do for check that the Video/GPU or Sram or CPU chipsets are OK?

> I read that the chip C6270 can be dead. How i can check it and confirm ?

I'll take any advice about White Screen problem, I really want to find a solution  

Thanks to all

[NightWolve]

Ah, definitely you should've changed all/100% capacitors when you started changing any - they are ALL leaking/failed/out-of-spec by now! You always want 100% new capacitors for NEC hardware to rule out any other problems! Before you continue, finish that job first.

[Lunacy]

Thanks !
  Ok I will change all Caps first and i will make feed back.

[Lunacy]

Hi

Full recap was done. Always white screen 

I dont know what i can check now.
No burning points on the mainboard.

What could I consider to be the cause of the problem? It is Hucard port issue or Gpu/cpu issue ?

It seems that the white screen can come from many sources.... i dont know where to start 

If people have some tips ! thanks to share it

have a nice day

[NightWolve]

Ah, too bad!

My advice:
1) Ask/PM @Keith Courage while he's around. He was just here by request.
2) Use the forum Search function for "white screen" - I'm sure I've seen old posts/threads about this problem in my years viewing this forum. There may be some lost clues somewhere in old posts.

Example: Here's a case that @thesteve (a pro EE & Turbo Expert) fixed with explanations of what was investigated/probed/etc. (he's retired though, you can't hire him).

EDIT: 3) To help out somewhat further, I reached thesteve on Facebook and asked for general advice on no-boot/white-screen failures, he said to check the reset pin and address lines!

Best of luck.

[Lunacy]

Thanks a lot.

For help myself, i just bought an new Multimeter/Oscilloscope for testing composants and some values.
I will test and share my results.

Yes i readed some topics with similars issues but each have differents reasons.. but you are right, there are many informations in each of these topics.

thank you to for asking the Thesteve, i will start as he said.

Pc engine will not died !

[Lunacy]

Hi,

I guess i checked Reset Pin. But i checked only continuity signal.

IC901 (C6280) pin 11 > HUcard port pin 36 continuity OK
IC903 (C6270) pin 24 > Hucard port pin 36 continuity OK

Is this the right way to test RST pin ? or i must to test something else (about RST)?

Thanks a lot 

[Keith Courage]

Unfortunately the problem you are describing(white screen) isn't usually caused by bad capacitors.

This can be caused by many different things. A bad 7805 voltage regulator, Bad traces or connections on the board(usually caused by corrosion under the hucard slot), a bad HU6280 CPU, or in some rare cases a shorted capacitor but this isn't usually the case.

Start looking for corroded traces or via hole connections under the card slot. Also check that all the traces for the card slot pins are good.

[Lunacy]

Hi Keith Courage,

Thanks for your reply and for your time.
I checked both regulator voltage and i obtained about 10V IN et about 5V OUT. Seems its Ok.
I checked many time the Mainboard and i dont see any burning traces or corrosion.
i checked under the hucard port for see all points and all pins, no corrosion or other.

i m so frustred  I want to understand what the problem is... even if I can't fix it.

> Im ready to test HU6280. PLease can you tell how to test ? i have another Working PC engine duo. Maybe i can take values from working console and compare with not working console ? Need osciloscope or only multimeter ?

Thanks a lot

[Keith Courage]

Sorry, I'm sure there are certain voltages that would give it away if the 6280 is no good but unfortunately I don't know what they are.

Anytime I've had a system with a solid white screen and all the other things check okay that I mentioned, then 98% chance it's a dead HU6280. So I just change it out.

What stinks is finding a replacement as these chips can only be found in other consoles.
Double check the traces under the board for the Hucard slot pins. If all traces test good to the 6280 chip, then the chip is probably bad.

Have you tried reflowing solder for the 6280 or 6270? Sometimes bad traces exist in between both of those chips causing the same issue.

Heating up/reflowing solder on the pins doesn't always permanently fix a bad trace but when heated up, a trace might start working again temporarily.

I will sometimes heat up each pin(for the HU chips) one at a time and then power on the console to see if anything changes. If does and the system starts working, you know which trace to run a wire to repair.

More info here
https://www.pcengine-fx.com/forums/index.php?topic=21837.0

[Lunacy]

Thanks a lot for your help !

I'll do everything you asked me to test and get back to you