Embryon MPU voltages/other problems

willymotts

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I just replaced the voltage regulator and the big cap on the solenoid driver. I now get no LED at all (LED is good) and two coils still lock on at power-up. I checked the MPU TP2 and it is 14.4 DC volts. The MPU TP5 is 5.14 DC volts. I need to get this thing to boot up and I need to find what is locking on the two coils. Some help here, please. Thanks.
 
Have you checked the driver transistors that drive the two locking coils? Usually a locked on coil is caused by a shorted driver transistor.

Edward
 
Have you checked the driver transistors that drive the two locking coils? Usually a locked on coil is caused by a shorted driver transistor.

Edward

Like Ed said you have several bad TIP 102 transistors and a locked on coil will pop the fuse for solenoid voltage on the main power board, the blown fuse will stop your MPU, it will not boot all the way up with this fuse blown. Sounds like you have other problems too. Find the coils that are locked on and unsolder one side of the wire (single wire on coil, most of the time not the yellow wire) this will allow you to get the fuse changed/stop blowing and get a little further in to it to find what else is wrong with the Game. Of course you will need to replace the drive TIP 102 for the final fix and probably new coils if they got to hot.
 
Like Ed said you have several bad TIP 102 transistors and a locked on coil will pop the fuse for solenoid voltage on the main power board, the blown fuse will stop your MPU, it will not boot all the way up with this fuse blown. Sounds like you have other problems too. Find the coils that are locked on and unsolder one side of the wire (single wire on coil, most of the time not the yellow wire) this will allow you to get the fuse changed/stop blowing and get a little further in to it to find what else is wrong with the Game. Of course you will need to replace the drive TIP 102 for the final fix and probably new coils if they got to hot.

True... you will get 6 flashes if the solenoid fuse is blown. He's claiming to have no flashes so you're right about the other problems. The seventh flash is for the zero cross detector which is generated from the solenoid voltage.

I would pull the solenoid fuse and get the MPU trying to boot and then move on to the solenoid problems personally. No sense trying to fix everything at once.

Actually... at this stage it's probably a good idea to test the MPU out of the machine and get it booting on a bench first. That's what I would do. Then pull the driver board and test the transistors.

You might have some bad transistors on the driver board. I wouldn't go so far as to say you do have bad transistors until you test them. Bad ROMs, a bad 6821 PIA or any number of other things could cause coils to stick on.
 
I would go so far as to say.....if his voltages are good (5VDC/12VDC) and there's no LED.....time to start digging through the reset section.

And yes, at this point, I would have pulled that to a bench too :)

Edward
 
I would go so far as to say.....if his voltages are good (5VDC/12VDC) and there's no LED.....time to start digging through the reset section.

And yes, at this point, I would have pulled that to a bench too :)

Edward

Depends what he means by "no LED". Bad reset circuit will cause a stuck on LED. Still... You're right it's the first thing to check when it's hooked up on the bench.
 
I'm on a bench setup and it's weird. I can sometimes get just a solid LED and sometimes one and sometimes two flashes. I can manually reboot it by jumping pin 39 and 40 on U9 but nothing is consistent. I'm considering the fact that this may be beyond me. That stinks because I'm in this hobby for the satisfaction of the "fix". Any ideas or do I order the new board at $200? Thanks.
 
I'm on a bench setup and it's weird. I can sometimes get just a solid LED and sometimes one and sometimes two flashes. I can manually reboot it by jumping pin 39 and 40 on U9 but nothing is consistent. I'm considering the fact that this may be beyond me. That stinks because I'm in this hobby for the satisfaction of the "fix". Any ideas or do I order the new board at $200? Thanks.

How are your sockets for the proms on the mpu board? Did you try reseating the chips? Those old sockets can cause some pretty flaky problems, especially if the board was working before.
 
Sockets look good. I cleaned the legs and reseated the chips first thing. For some reason (!?), I now have a fairly consistent 2 flashes.
 
I did the whole corrosion rebuild with the kit from Ed. The problem is that some of it was really bad. I'm not sure that I got all the traces rebuilt.
 
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