PC engine burning smell + green/white/ blue screen

[Tengugurl]

Hi!

bought a White (original) PC Engine off ebay and was sad to see it was faulty.

Overview:
I am greeted with different color screens each time I power the console on and off with a game inside.

Also, it smells like burnt electronics every time the console is turned on. (Especially near the back extension port). Which is odd as I am using a stepdown converter that I have used on all my Japanese consoles.

Mitigation steps:

Having done some research on this in my late-night repair video searching (We all do it if we enjoy fixing things lol) and I had found out:

Problems:
1) The Green/White/ Grey/ Blue Screen boot screen (One color or the other depending on the consoles mood) means
* Game is not read and the AV works on the console

2) Checked the Fuse (Fuse does not shown blown)

3) Checked the Caps and they don't show any corrosion nor bludging.

4) Check the 7805 (checks out 5v no issues)

5) Check the traces for cuts, and or damaged CPUs, or GPUs . (All looked fine, though I have not seen a schematic to find shorts)

6) Clean with IPA while searching for issues (Done and still no issue, even tried removing the HuCard a bit while powered on and no change

7) Felt for heat/ hot parts to see if something was shorting but nothing got hot?

Questions:
1) What could be wrong with the console? If the following look good:

A. Good caps
B. No burns/scorch marks
C. No blown fuse

If this thing is smelling like burnt electronics, yet nothing is hot, what could be causing this?


Looking forward to any assistance that can be provided.

It's super hard to find PC Engine/ Turbo Grafx16 documentation/ fixing examples on the internet.

[PDiggity]

How long are you leaving it on - Is one chip hot after a time?
Which power supply are you using? How much voltage is it actually outputting?

[Tengugurl]

Hi there!
Leaving it plugged in for a matter of seconds.
No chip is getting hot. (Felt the RAM, Felt the GPU/CPU) and nothing.

Checked the power rail getting a solid 5v off the 7805 and everything down stream is receiving 5v+ correct.

The PSU is a 9v unregulated NEC PSU that came with the console. It's pushing out 13v center negative but the step down is taking place correctly downstream.

It smells awfully and it is frying Hucards now
I bought a backup PC Engine and sure enough I put a Hucard into the damaged one it fries it and it gives me a white screen on the Good PC Engine. (not going to try that in fear of it spreading to my good console lol)

I've seen a few videos online and I am really thinking I need to logic probe this bad boy and replace a component.

Idk.. caps look good but it's not posting so I am thinking graphics arent being sent to the HUc6260 idk..

Sucks!

[PDiggity]

An inexpensive logic probe would probably help you. I bought one for $15 last summer and it was enough for a few projects.
This sounds like a scary little pce! It's definitely sending mixed signals all the way to the Hucard slot...
I had an issue like this on a Game Gear recently, where it was dragging some pins from the cart slot low to ground and shoring them out. It was killing sram...
You could try checking for shorts at the card slot, or measure the voltage, if you don't have a probe. That would probably lead you to the problem.

[Keith Courage]

unfortunately a solid color screen usually means a bad 6280 or 6270 chip on the board in which case then it's usually not worth the cost to repair.

However, in some cases it can be a bent or out of place pin in the hu card slot or even a broken connection for one of the wires of the gray ribbon cable inside. Check in the hu slot with a flash light to see if you see anything out of place. It is common for wire or two on the ribbon cable to break if someone had previously opened and closed the system many times. Basically moving the ribbon cable back and forth too much can break these connections right where they connect to the board or upper hu slot area.

Also, just to mention something easy to try...Have you tried backing the game out of the card slot slightly before powering on? Sometime games require this if the slot pins or games pins aren't meshing up perfectly.

[Tengugurl]

Thanks you two for replying!

Ugh... Yeah that's kind of what I was hoping wouldn't be the case and you are right, might not be worth it as PC Engine systems are decently priced Right now compared to a Turbo Duo or GT.

There is one place online that is selling the parts for $14 a pop but id really have to do some logic probing to see if it's one or the other. (my luck both!) Haha

Had a look and the pins look good and I am geting full continuity.

Anybody want parts? Haha DM me lol..

If there were diagnostic bios or more documentation like the neo geo has I'd be more willing to dump time into it but, there are only a handful of vids/service manuals and posts on that to feel confident enough to see what the 6280 or 6270 should be reading. (High/low)

Unless someone knows of a good wiki page on this?