Dirty Harry not starting up

[kevin]

When I turn the power on, the appropriate LEDs on the boards light up, but nothing else happens. The problem started with the game just shutting off completely after a couple balls. Now it won't do anything.

I am assuming it is a component on the power driver board. It looks like Clay's guide for WPC has been taken down (which is the only way I have been able to diagnose things with a DMM). I did notice that there was a blown fuse, known as F110, on the board. I can't tell what goes through it by looking at the schematics. I did check the diodes and transistors that are near it on the board. The only unusual readings I found were two diodes right next to it that were reading .5V (while all the other diodes on the board had much lower readings). I'm not sure this would be the problem. The row of transistors seemed to all have similar readings (though when I was testing one of them with the power on, it caused the GI to turn on).

Any ideas on what I can check?

[eric]

F110 is a GI fuse and probably an unrelated problem.

Test the 5V and 12V test boints on the power driver board. What do you see?

[kevin]

5V and 12V on the power driver board seems to check out fine. I'm assuming that this means this board is probably fine and I should be looking at the MPU board?

[eric]

What was the exact voltage reading at the 5v test point? If this is below 4.9V you will have problems.

Test the voltage at pin 32 of the game ROM on the MPU. You should see the exact same voltage at the 5V test point on the power driver board. If it's lower you have a connector issue.

[kevin]

I can't tell which pin is 32 (there is no label saying which is 1 or 32, etc.). The pin at the top right is 4.76V. Bottom right is 4.98V. The test point on the power driver board was 5.02V. Maybe this means I have to reflow the connector on the MPU board?

[eric]

The bottom right corner is pin 32 and 4.98V is good. What do the 3 diagnostic LEDs on the MPU do when you power on the game?

[kevin]

D19 and D21 are on. D20 is off. There is no blinking or anything.

So I found Clay's repair guide....it's making me think that maybe the game ROM is the problem. He mentioned that it can go bad if there is no sticker over the little window on it. Mine didn't have one (it was conveniently stuck somewhere else on the board).

[eric]

The EPROMs are erasable when exposed to UV light. It's possible the game ROM could be bad.

Does D20 flash at all when you turn the machine on? IIRC, one flash is indicative of a bad game ROM.

[kevin]

It does not flash at all.

[kevin]

Jake told me to pull the ribbon cables off the MPU board and try to start it. It booted. I reattached cables until I found that the fliptronic board was the problem. It looked like this.....



I'm guessing that the transistor in the middle is the problem. There is a little of that white shit on the board. What do I use to remove it?

[eric]

Hmm, that looks like heat sink compound to me which I don't think is necessary in this instance since the transistor clearly isn't attached to any sort of heat sink. I haven't done a lot of work on Fliptronics boards, but my guess is Q5-12 are probably just screwed to the board to prevent ops from accidentally shorting them against the larger TIP36 transistors.

Q7 was definitely replaced at some point and possibly Q5 too. You can tell by the residual flux around its leads (and the fact it's the wrong part!). Since it is the wrong part (albeit one that's nearly identical to a TIP102) I'd go ahead and replace it with a TIP102 and clean up the white stuff with high percentage isopropyl alcohol. Definitely test all of the other driver and pre-driver transistors on this board too.

[eric]

That said, even if this transistor is shorted I don't think it would cause the MPU to lockup. A shorted transistor would lock on its associated coil then blow a fuse. Do you have another ribbon cable you could swap out?

[oneandasixtenth]

Q 9 appears to have a bit oF solider sticking out the top ?

Eric.. god

[DDT]

That poor dead soldier.... At least he gave his life doing what he loved...