• Please review our updated Terms and Rules here

Weird Screen Output

A

agirivera

New Member
Joined
Oct 12, 2008
Messages
6
Hello to all.

I'm in the process of reviving the first computer the family had used. I tested the video card in another computer and it works just fine.

I cleaned the 286 motherboard. It's an ACT mobo with a Siemens SAB 80286-12-N. Here's the link for it: http://artofhacking.com/th99/m/A-B/30273.htm

On initialization, it produces a weird output:

2934579614_5b0eb18040.jpg

I am wondering what this is.. I removed the battery by the way, it was leaking. Had anyone encountered this before? Any info would be appreciated. Thanks...
 
probably your power supply. bad or insufficient output. that's my guess. i don't think it's the RAM, because thats obviously video RAM that you're seeing the garbage from. it looks like a repeating pattern, not just random garbage so i think when it initializes, the power it's being fed is not correct thus it initializes all the bytes to some weird random yet consistent value rather than 0 in the VRAM.

maybe.
 
Last edited:
I swapped the power supply to one that's known to be working. Still the same cheese, garbage with red background.

I connected a speaker just in case this might mean something to you guys. The beep message is . . - - - - - - - -
 
agirivera said:
I swapped the power supply to one that's known to be working. Still the same cheese, garbage with red background.

I connected a speaker just in case this might mean something to you guys. The beep message is . . - - - - - - - -
Click to expand...

i don't know about the beep codes, but it might be worth unplugging any internal devices not needed. just keep the motherboard and maybe 1 floppy drive connected to the power and see if it helps. while you're at it, keep nothing plugged into the ISA slots except the video card. you know that's good, like you said.

if not, bad RAM? somebody else probably knows a good place to find the beep codes.
 
actually the video card is the only one that's plugged :) guess it's the ram then huh..
 
That I do not know for sure. But I think it is native, the CPU is marked as 12MHz. Plus the mobo has got jumpers for 16MHz too.
 
agirivera said:
That I do not know for sure. But I think it is native, the CPU is marked as 12MHz. Plus the mobo has got jumpers for 16MHz too.
Click to expand...

CPU speed is different from ISA bus speed. take a look at that page you linked with the mobo layout. whatever jumper 17 is set for, try switching it and see what happens. you might also want to try changing jumper 13 to the other setting. in fact, try that first.
 
agirivera said:
Did both, still the same... :(
Click to expand...

Well, from the looks of it, because the output is not a random pattern, something (and it could be anything) seems to be causing a stuck bit on the bus.

Might be a support chip, might be a TTL, might be, just about, any chip on the board.

You could try replacing the RAM, it's as likely as anything else at this point.

How much and what kind (256K or 1M) of memory modules are in the board?
 
I checked the damage from the leak but it is pretty much isolated on the area where the battery was in.

I found another 2 set of compatible chips (44256). I swapped them both. The only thing that changed on the first swapping was no screen output with 3 short beeps. However, it reverted back to the red background when I reseated the chips. You guys might be right that some support chips might be the culprit.

Well I guess I have to pull the plug. Thanks everyone for the help. It wasn't a loss, I enjoyed the adventure...
 
Where are you located? If shipping isn't too bad, I'd like to take a crack at the board.

Hate to see an old MB that doesn't work.

Ya know, I just thought of something. Perhaps the video RAM is sitting in the middle of the system RAM for some reason known only to the video card.

Have you tried another video card? A Herc or other monographic might be a good place to start.
 
You must log in or register to reply here.
Back
Top