4 slot board: slot #1 doesn't work!

Okay, I've had my 4 slot board for a while now. I decided to do the audio cap kit to fix the low volume issue. Well all was well, except my slot #1 does not seem to work any more. I cleaned all 4 of my slots (which worked great for the other three, BTW) but even when I just put a single game in slot 1 and nothing in the other slots, I always come up to the test pattern, like it doesn't even see the game in the slot!

I also tested each pin with an ohmmeter to see if it was making contact to each trace on the cartridge and it was. Could this be a bad 74xx IC on the top board? Is there anyway to test which is good and which is bad?

Channelmanic, please feel free to chime in!

Come on! Somebody's gotta know something about this!

It's difficult to troubleshoot top board issues remotely.

The problem is if the cart isn't 'seen' by the board it won't send signals to the cartridge program ROMs to try and 'read' them. If it were a graphics ROM issue then you could take a cartridge apart and insert the boards separately in the slots. Then you could take a logic probe and look for a missing address signal at the cart and fix the bad trace.

What I would to to try and fix this one would be:

A) Clean the slot
B) Clean the cart
C) Find the 74LS138 (3 to 8 data selector) in the corner of the board and check the inputs to the chip to make sure they are there. If not, trace backwards.
D) Trace out the 4 cartridge select lines from the 74LS138 to make sure one of those isn't broken
E) Trace out the program ROM address and data lines back to the chips (74244 bus buffers on the address lines and 74245 latches on the data lines) and look for broken traces.
F) Trace out the connections from those buffers and latches back to the connections to the bottom board and look for broken traces.


It almost has to be something on the top board as all the address and data lines connect together on the top before going to the bottom. The only thing that could be causing it from a bottom board perspective would be the control signals going through some latches to the 74LS138 data selector IC.

RJ

Did you get it checked out or did I go too far over your head?

*Bump from the dead*

Whoohoo! I fixed this board! I was looking around for bad traces and couldn't find any. I decided to just hose the board down because it was pretty dirty. Now it works! It's strange though that it just quit working all the sudden, despite working just fine before.