Repair: traced issue back to U32, replaced U32, would boot but video cuts out before rom test, replaced revision roms and replaced U45 and U47, boots.
e:
I actually backtraced it going back to U32 as well, so I might try removing that resistor to see if it removes the short tomorrow then maybe look into swapping U32.
e2: looks like it removed the short.. so something around u32 is causing the short or u32 is bad..
For the hell of it I tried booting it up, and now it will output that staticy garbage screen when you first power on the board, but the colors are kind of a rainbow gradient, and it blanks out when it goes into rom check. But at least I know video works! So now to work on that top left corner... Also this is a early-mid 95 Wolf unit, which seems to have some revisions over my 94 wolf units.
e3: Decided to just to swap U32 from a parts board, and now I get the classic purple screen, into garbage, but it's a little different, it'll stay solid purple, then garbage will come up, then it'll blank out again. Short seems to be gone after replacing U32 but I'm not out of the woodwork yet.
original post:
I have a wolf unit board here, that I put away months ago because I couldn't figure out the problem. It plays blind, but has working sound and seems to pass rom check. It hasn't been messed with outside of me socketing U91 and U75. U91just to see if that would fix not having video (it seems to have sync, just no video) and U75 because I was getting the incorrect outputs on the hex inverter, but that didn't fix anything. I have noticed I get a 100 Ohm reading between VCC and GND on every IC/eprom, on my other wolfunit I get like 220~. I've already swapped U45 and U47 with known working ones, so that's not the problem.
I do have continuity between ground and pin 13 on the hex inverter (74F04) and I have tried swapping that part out and that didn't help. I traced it back and pin 13 gets it's input from pin 1 on U91 (7407N) removing both of those parts, that short to ground still remains, so I'm not sure where this one is coming from
e:
I actually backtraced it going back to U32 as well, so I might try removing that resistor to see if it removes the short tomorrow then maybe look into swapping U32.
e2: looks like it removed the short.. so something around u32 is causing the short or u32 is bad..
For the hell of it I tried booting it up, and now it will output that staticy garbage screen when you first power on the board, but the colors are kind of a rainbow gradient, and it blanks out when it goes into rom check. But at least I know video works! So now to work on that top left corner... Also this is a early-mid 95 Wolf unit, which seems to have some revisions over my 94 wolf units.
e3: Decided to just to swap U32 from a parts board, and now I get the classic purple screen, into garbage, but it's a little different, it'll stay solid purple, then garbage will come up, then it'll blank out again. Short seems to be gone after replacing U32 but I'm not out of the woodwork yet.
original post:
I have a wolf unit board here, that I put away months ago because I couldn't figure out the problem. It plays blind, but has working sound and seems to pass rom check. It hasn't been messed with outside of me socketing U91 and U75. U91just to see if that would fix not having video (it seems to have sync, just no video) and U75 because I was getting the incorrect outputs on the hex inverter, but that didn't fix anything. I have noticed I get a 100 Ohm reading between VCC and GND on every IC/eprom, on my other wolfunit I get like 220~. I've already swapped U45 and U47 with known working ones, so that's not the problem.
I do have continuity between ground and pin 13 on the hex inverter (74F04) and I have tried swapping that part out and that didn't help. I traced it back and pin 13 gets it's input from pin 1 on U91 (7407N) removing both of those parts, that short to ground still remains, so I'm not sure where this one is coming from
Last edited:
