Teenage Mutant Ninja/Hero Turtles RAM fault

This one is a simple fix but I thought I’d use it to demonstrate a technique for making minor track repairs.  I received a TMHT PCB today which on testing showed this mess:

While the screen is a complete mess, you can make out a number of ‘OK’ and ‘BAD’ messages.  With this many problems and one ROM affected, it seemed best to start with address lines on the ROMs.  Immediately the one at J15 turned out to have a disconnected pin 4.  The address lines are shared between ROM and RAM near the CPU, which meant there needed to be a broken track somewhere.

And this is what I found tracing a track just hidden under J17.  This is very likely to be the result of someone trying to do a 4 player to 2 player ROM conversion, and being careless with a screwdriver.  There’s a somewhat tidy way of fixing small track breaks like this without leaving a big jumper wire on the game.

First scrape some insulation off the track and ‘tin’ some of the copper – liquid flux will help here, just a tiny bit.

Next you need a couple of strands of thin wire – here I just split two off from some fine gauge multicore and twisted them together.  Tin those too.

More liquid flux, and solder the exposed tinned wire to the tinned tracks.  It’s usually easier to do than this but the socket was kind of in my way, and I didn’t want to go through the invasive and time consuming process of removing and refitting it.  This is why we leave some insulation on the wire, to use as a handle.

Then use a razor blade to cut the handle off, leaving a few strands of wire as a track repair.

Tidy up your work by cleaning away the flux and using some masking fluid to cover up the exposed track.  Again this can be done a little tidier when you don’t have a socket in your way.

Looks fine though when it’s all back together, and the game is repaired!  Actually it did have a sound fault too, it would sometimes make intermittent rumbling pops, the 12v filter capacitor had been knocked, damaging it.  Another easy fix.