Black Screen CreatiVision

[cheshirenoir]

So I've been working on my CreatiVision.

So I have fixed Phi by finding a trace broken. Similar on the NMI (Which wasn't being pulled up) traced to a bad via.

I've also fixed the trace I broke. (Whoops!)

Now I'm stuck with all Address lines pulled high, and all but D0 pulled high on Data.
Phi in and out looks good. NMI and RESET both go high in a timely fashion.

Known good 6502 (From my Apple IIe) and the ROM checks out OK. I even made a replacement "just in case".

Working Sonic Invaders cart in the machine.

Have I missed anything?

Thanks in advance,

John

[cheshirenoir]

OK it looks like there are some significant degredation of the vias on this board. I've been bodging and fixing all day.
Fixed three address lines and two data lines and now I have activity all over the place. Still no picture though.

[Scouter3d]

Hi Chesh,
wow - is there corrosion on the board to destroy vias? Are the solderjoints dull?
Good luck! TOM:0)

[cheshirenoir]

Solder joints are dull, and I think this may have been a "friday afternoon special".
Most of the vias wren't flowed all the way through, and the same applied to many of the legs of components. There was pits and cavities in many of the solder blobs too.
No obvious other hints of corrosion.
I've since discovered that there's no clock getting to the TMS9928 so I'll look at what on earth is happening there next.

[Scouter3d]

"Friday afternoon special" sounds nice in austria we say "monday-car" :0)

[cheshirenoir]

That circuit around the clock is a mess! Currently both pin 39 and 40 of the TMS are being held high and I can see no oscillation of the crystal. The clock circuit winds through a different part of the circuit, and, of course, there's no silkscreen so I'm having to trace over both halves of the board. I can't even find L2 so maybe it's not on this revision?
I'm leaving it for this week. I'll probably have to try and sraw out what each component is, and what it connects to in that area.
Argh!

[Scouter3d]

Hi Chesh,

do not despair, i know you will get there!

meanwhile happy easter!

Cheers, TOM:0)

[Mobsie]

Oh wow… i hope you get it.
Happy easter

[cheshirenoir]

Haven't given up, not by a long shot. If I have to I'll see about rebuilding that circuit to test out of the board.
Whatever is going on there, it's not happy.

Actually, has anyone got a 700305 model (Early PAL with RF box on a riser) that can take a hi res photo of the top right corner? This is the area next to the 6502 and the cartridge slot with a crystal in it.

Someone has done rework on mine and I think they may have scrambled some components...

(Hi res photos of all the boards could be a useful resource for the main site, especially if we labelled all the components to match the schematics)

John