Dirty Harry

 

Last weekend I got the Dirty Harry I had visited onsite a while ago in to the workshop for an overhaul. I already know it has problems ejecting the balls and the ball sticks by the lock magnet but before starting the disassembly I spent a couple of evenings playing it to find out what other faults and problems it might have. The left slingshot is dead, the left diverter pinches the ball when it should be diverted to the right and the cable loom in to the moving gun has a contact problem. It's enough to just touch the loom to get the switch to change state in the switch test. It should also have a reboot problem but I haven’t seen that happening even though I played it quite a lot.

I started with the ball eject problem. First I was quite sure it was related to the optos in the ball trough since the switch test indicates that the balls aren’t in there. But instead it turned out that the balls has been magnetized and sticks to the ball trough instead of rolling down where they should be to triger the optos. I could pull all four balls after each other, almost like permanent magnets. I tried to demagnetize the balls using a degausser for CRT tubes. The balls lost the magnetic but after a day or so it was back again. These balls are probably chrome steel balls which are prone to be magnetized. I will replace them with four new carbon steel balls which are not as easily magnetized.

Next I looked at the problem with the magnet and the balls sticking to it. This is not due to the magnetic balls, it is pure mechanic. I have put my fingers under the ramps feeling at the magnet core and it sticks up a bit too much over the playfield but it is hidden under the ramps so it’s not possible to see what it looks like.

When looking at the playfield it seems to be quite simple since there is a lot of open space. But the ramps are tangled in to each other in a way that makes it complicated to disassemble the playfield. It took some thinking before I figured out where to start. This is the parts I had to remove to access the top of the magnet, disassembled in order from left to right, assembly will be done in the reverse order. There are more bits to remove before I can start cleaning and changing the rubbers, but that will be done later.
 

The magnet turned out to be a tricky problem. It has been a bit too high for a long time, probably since the game was new. The balls have been beating the magnet core and now it’s almost like a nail head. It’s not possible to pull it through the hole in the playfield anymore and it’s not possible to screw it upwards and remove it from the upside, I’ve tried with my largest screwdriver but can’t get It to turn.

 

 

 Look at the bracket above the magnet, thousands of balls have been bouncing up from the magnet and making quite a dent in it. This must have been destroying the balls and the balls in the game are in good condition, so they must be quite new. Just a pity they didn't bought carbon steel balls.

 

I need to think a bit about this problem to figure out how to get the magnet out of the playfield. Maybe I can use the Dremel to cut groves in the core to be able to fold up or wiggle off the edge allowing the core to pass through the hole. I do not want to cut too close to the edge and maybe damage the playfield.

EDIT

If the tool isn't big enough then just get a bigger one. I went over to a friend and borrowed an XL screwdriver with square shaft. And with some help by a wrench I managed to loosen the core. It had been beaten down in the playfield, that’s why I couldn’t turn it. After a quarter of a turn I could easily get it out by hand and here it is.