Supergrafx won't boot up

[Duo_R]

Update - FIXED

Was a bad trace (corroded) coming off pin 79 of a HU6270 (the chip closest to power switch). Just jumpered and all good now.

OK I recently posted how i obtained a Supergrafx unit. I bought it knowing it was a repair unit but I was hoping just a bad fuse. Doesn't seem to be the case. The fuse is fine, I just tested the voltage regulator and it's getting 9.5v in and outputting 4.99 on the out pin.

I replaced the 470uf cap that looked like it was going bad, cleaned up the board and everything visually looks ok no cracks. The shielding on the bottom did have blobs of solder that disconnected and I resoldered those. When I power on I get white screen then it goes all black. So appears to boot but nothing happens. Any tips on common issues ? I'm a sucker for repair systems. ;-)

[Duo_R]

Additional info, just measure pin 40 on both HU6270 chips, getting 4.99v on both.

[mickcris]

i would check closer for cracks.  look at the pics i linked to and check those areas carefully.  it took me a few tries before i found all the places on the board that had broken traces.  they can be hard to see unless you use a eye loop or some kind of magnifier.

https://www.pcengine-fx.com/forums/index.php?msg=399144

some cracking on mine was under the hucard slot and also under the ground shield.

[BlueBMW]

Supergrafx are crazy prone to cracking in the middle of the board near the plastic post that supports it.  I've seen this several times now.  Repair all the broken traces from the crack and remove the post

[Duo_R]

Dang I don't see any cracks. I really don't want to remove the hucard slot if necessary but maybe I need to.

[Duo_R]

Hucard slot removed, use magnifying glass and tested a bunch of traces. All seem ok.

[Duo_R]

Ok so Steve was helping me troubleshoot this one. He noticed a corroded trace near the heat sink. I totally didn't see but he saw it in a photo I took. And we have a working Supergrafx! At least it's playing a PCE game! Now to test the Supergrafx mode!!!! Yeah!!!!!!!

[Duo_R]

I just had to send one jumper, no cracked PCB but just a corroded trace going to Hu6270! I almost swapped in another ram chip but looks like the one I got is good!

[Duo_R]

TheSteve - you rock man thanks for spot checking!

[BlueBMW]

If you still have it open you may want to cut out that center mount post since one good drop of the console can crack the pcb from that thing.

Congrats on the fix though!

[Duo_R]

Ok so it is fine without the post?

[BlueBMW]

i mean you can leave it if you want, we've just seen a lot of cracked boards right in the middle and it seems to stem from an outside impact pushing that mount post against the board and cracking it.

[Duo_R]

Ok just want to make sure it's stable without. Thanks man!

[mickcris]

It is. Really serves no purpose. I have cut it off on mine. Thesteve recommended doing it.

[Duo_R]

The post near the green switch?

[mickcris]

No. It's the one on the other side of the slot. It does not have a screw hole in it.

[thesteve]

bottom cover
sits between the slot screws

[mickcris]

I guess i cut the wrong one off.  Cutting that other one though did not make any difference in the stability of the board in the shell.

[Duo_R]

Ok so this guy?

[NecroPhile]

Remove the pencil before reassembly. 

[Duo_R]

Ok so this guy?

Remove the pencil before reassembly. 

Why? It's a rare gold one!!!

[thesteve]

yes that guy
the slot is screwed to the top cover so when the system compresses that post pushes up and the slot pushes down causing the board to snap