6-Slot Bad Top Board Logic

[chaoticjelly]

Guys,

I have Evil Aidy's 6-Slot MVS here which he originally sent to me with a Video RAM problem. That is now fixed..

However, I am getting the exact same problem as in this thread;

http://www.neo-geo.com/forums/showthread.php?t=143240

As the thread states, "vertical lines" on every single slot. Hardware tests do not throw up any errors, and the hardware test does not test any of the top board logic chips right? The vertical lines don't appear in any system menus, UniBios menu etc..

As the thread states, "The 74F251APC multiplexers I discovered any one IC can be associated with all 6 slots." - I have checked all of these with a logic probe, and they all seem to have the exact same signal on each pin..

Does anyone have any ideas as to which logic chips to try and check next? Which others are common to all slots? This fault didn't exist before the Video RAM went bad.. and I have been nothing but careful when I removed the top board from the bottom board.. so doubt it is a broken trace etc..

Here are a few pictures of the fault;

Thanks in advance.

 

[ttooddddyy]

Those ICs can get hot when faulty, touch test them and look for blistering on the surface.

 

[chaoticjelly]

Those ICs can get hot when faulty, touch test them and look for blistering on the surface.

First thing I tried mate... as far as I can tell, none of them get discernably hotter than the ohters...

 

["Evil" Aidy]

Are you still there chaoticjelly? A PM sent...

 

[channelmaniac]

Look in my repair logs... there's a post on how to find & fix those lines.

 

[mainman]

Guys,

I have Evil Aidy's 6-Slot MVS here which he originally sent to me with a Video RAM problem. That is now fixed..

However, I am getting the exact same problem as in this thread;

http://www.neo-geo.com/forums/showthread.php?t=143240

As the thread states, "vertical lines" on every single slot. Hardware tests do not throw up any errors, and the hardware test does not test any of the top board logic chips right? The vertical lines don't appear in any system menus, UniBios menu etc..

As the thread states, "The 74F251APC multiplexers I discovered any one IC can be associated with all 6 slots." - I have checked all of these with a logic probe, and they all seem to have the exact same signal on each pin..

Does anyone have any ideas as to which logic chips to try and check next? Which others are common to all slots? This fault didn't exist before the Video RAM went bad.. and I have been nothing but careful when I removed the top board from the bottom board.. so doubt it is a broken trace etc..

Here are a few pictures of the fault;

Thanks in advance.

I did fix that board in the post you quoted but its been a while and many, many, many more faulty and fixed 6 slots have come after it.

If you where in the U.S I would look at it for free for you. Best I can recall is it was in fact related to the 74f251 IC, which one was either faulty or a broke trace was the problem.