I just bought a Road Kings project that will not boot. The 7 segment display shows a solid 8 at powerup. And I get the single tone. The board is very clean and shows no sign of acid damage, or history of repairs. I did confirm battery voltage at battery holder and nearby diode. Machine will respond to coin drop with audio, and can hear a very faint 'chug chug chug' if you press the start switch but nothing else. Checked voltages on power supply and I believe they all check out per online references. Nothing comes on any of the displays. Machine will not go into attract mode. (I don't think)(no lights ever flash on playfield, but if left on, sometimes plays audio) If I play with the adjustment buttons I can blindly come across audio test which all work. I almost think I have dead displays AND mpu problems, which will really suck.

New batteries installed and checked voltage with machine off, good. I did replace all caps and high voltage section of power supply and still have exact same problems. Also reseated roms and went through most connections. Press the CPU button on the mpu board and after a second or two the 7 segment display shows a distorted 3, the upper right segment of the 3 is blank.

Reading dozens of posts it sounds like an MPU problem, which is a little out of my comfort zone.

Where to next? any specifics I can check before I try and find someone to send the MPU board to? whats the going repair cost for an MPU board? Board is really clean.

Thanks

mope~

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Well, while checking over some simple things before I decide to send this MPU out, I checked my trough switches and found one out of adjustment. I adjusted it and it will get closer to starting a game. It will play game music and switches will respond with noises and effects. I get no controlled lights lighting on the playfield, just a handful of GI stay on.

No flippers or solenoids are working. I do have 71 volts at the flippers. And by tripping the transistors with a ground wire I can get most solenoids to respond, but not the flippers.

I read somewhere that by pressing the red switch inside the coin door, i should hear the relay on the mpu click....it doesnt. At a quick glance it looks like Q8 is controlling the relay. If I trip Q8 with a ground wire my solenoid fuse blows.

I will play with this thing a little more and see what I find. Any suggestions?

Thanks

I assume the cpu is not booting properly since I show an 8 on display, I guess it should show a 0 when it boots properly.

I will dig into the relay a little more.

Grumpy,

Thank you for the input. I will get back to this machine this weekend and see whats up. I will sit with a notepad and get some voltage readings and take a closer look at the relay.

So I got 5 mins of free time to check some other minor things....

I pulled all plugs off the board except the power and still get the "8".
I measure 4.9vdc at the batteries and at the 1st pins on the roms, ac ripple of .002vac (I did change caps on power supply already)

I dont know where exactly to check 'blanking' voltage but found a test point marked 'blanking' but i only get .074vdc

I am timid to cut the diode off the board for the relay yet because I dont want to start chopping on the board if i might be sending it out anyway. Could the diode for the relay or the relay cause the board not to boot?

Thanks guys, I am sort of a noob and appreciate the step by help.

~mope

12.8 vdc on zener, 6.5vdc on the other side. .200vac on both sides.

So I pulled the board....and I am glad I did, Q75 has been replaced at some point, which I didnt notice with it in the machine. And Q7 has a piece blown out of it.

See attached pictures for more of a trained eye inspection.

Thanks in advance.

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My main concern obviously is still that the board does not boot. I have OK soldering skills to attack the transistors, so I am not worried about those so much. In my mind neither would cause a no boot situation. BUT, my personal diagnostic experience has been less than useful on pinball machines so far. I know how one thing effects others down the line.

I guess what I am saying is I don't want to mutilate these parts on the board if I am going to end up sending it out anyway.

Let me know what you guys think.

I do not have a logic probe. While I would love the learning experience...board work scares me.

For a couple bucks to have someone that knows what they are doing take care of it is more my style. I am a good parts changer, but that might be about it. I had thought about ordering a new set of ROMs and CPU just to try, but John Wart includes them with his repairs, so I may just go that route or another board guy.

I dunno sometimes I am cheap....and sometimes I know when I am outside of my comfort zone.

Thanks for all the help, I am going to get this board out and see what happens. I know I have some other things to address with this machine, I will have some time waiting on the board to go through the playfield and make sure all is good.