Data East / Back to the Future boot problem

m_mcgovern

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[cross-posted from r.g.p]

I am getting sooo close to my BTTF working again.

Game was working fine (except for one playfield switch and a ton of #89 flasher lamps and #47 lamps, mostly in the backbox).

I replaced all of the bad lamps...now the game won't boot!

I get the normal Data East LED boot sequence:

- PIA / +5V LEDs turn on immediately
- PIA LED turns off
- Blanking LED turns on next
- A fast voice sample is played ("Back to the Future")

After the LED sequence/voice sample, I do not get any message on the display, nor does the playfield/backbox attract mode light show start. I cannot coin up a game, nor advance out of test mode (so it is not just the display being out, although if that were the case, I would expect the light show to be running)

I've re-checked my coils and none are shorted. I have 4.9V on the 5V test point when measuring to the right of the batteries.

Could the extra lights be drawing too much current and creating a problem at the CPU board? What else could it be?

Any help is greatly appreciated. I thought once I got the lamps in place I would be 98% there, but now it feels like I've taken 5 steps back!!
 
Sounds like the CPU, probably a 6802P chip right under the batteries. If there has ever been acid damage it may have finally done it in. I also have found cold solder joints on these (notoriously). I would pull the board, resolder all the header pins and the CUP chip. If there appears to be any damage at all on the CPU I would replace it and the socket.
 
I have a similar problem on a DE WWF royal rumble I am putting back together. Checked the 6802 (6808) chip and it was toast. Lots of acid damage. Chip legs broke off in the sockets. Socket very corroded. Have a new 40 pin socket and chip on the way to see if that will fix it. Will let you know if helps. Those batteries at the top of the board can do a lot of damage as the acid makes it's way down the board. I also ordered a new game eprom just in case.
 
@GregM-- I see a bit of acid on one of the internal battery holder pins. The chips surrounding the holder look to be fine (I'm not sure if there is anything under the holder...I will check that tomorrow) and the traces above/below board appear to be fine, just the metal tab that runs from the holder and is soldered in looks to be damaged.

Also, this BTTF has a Rottendog power supply board in it. It looks like the CN1 connector was not fully plugged into the power supply pcb (labeled CN1X12 on the Rottendog schematic). Perhaps opening/closing the backbox lightboard was enough to disengage it partially.

Tomorrow I will replace the holder with something remote.
 
Might also remove 6802 inspect it and put it back into the socket. If there is an issue you will see it then
 
Update!

OK. I did the following:

1) Removed the battery holder
2) Neutralized the battery acid at the battery holder solder pads
3) Cleaned up the header pins on the cpu pcb.
4) Found a loose wire on one of the coin counter switches in the coin door
5) Reconnected the cpu pcb w/o batteries
6) made sure the CN1X12 harness was plugged in well to the power supply

Now, the pinball boots and plays! :D
It is about 98% complete now...the remaining issues:

1) I still have a few lights out, despite replacing the bulbs. I don't think it is a broken wire issue as the missing lights are not all in a single column or row. What else is there to check? The diodes maybe or perhaps bad socket?

2) the left ramp switch is not functioning, despite getting a new switch wired in. I'm at a loss for what may be wrong as the switches both before and after it on both the row and column work...

3) Voice samples are low compared to the sound effects and the music. I think I need to recap the voice sample section of the sound pcb to fix this.
 
OK. I did the following:

1) Removed the battery holder
2) Neutralized the battery acid at the battery holder solder pads
3) Cleaned up the header pins on the cpu pcb.
4) Found a loose wire on one of the coin counter switches in the coin door
5) Reconnected the cpu pcb w/o batteries
6) made sure the CN1X12 harness was plugged in well to the power supply

Now, the pinball boots and plays! :D
It is about 98% complete now...the remaining issues:

1) I still have a few lights out, despite replacing the bulbs. I don't think it is a broken wire issue as the missing lights are not all in a single column or row. What else is there to check? The diodes maybe or perhaps bad socket?

2) the left ramp switch is not functioning, despite getting a new switch wired in. I'm at a loss for what may be wrong as the switches both before and after it on both the row and column work...

3) Voice samples are low compared to the sound effects and the music. I think I need to recap the voice sample section of the sound pcb to fix this.

Good job on your repair work. Regarding the lamps, I've had several DE games with non working CPU controlled lamps and in almost every case it was the diode. You wouldn't think that a diode for a lamp would fail, but they must have used some pretty cheap parts. And while you are at it, double check the diode for the switch on the left ramp (orientation and if it is good.)
 
Good job on your repair work. Regarding the lamps, I've had several DE games with non working CPU controlled lamps and in almost every case it was the diode. You wouldn't think that a diode for a lamp would fail, but they must have used some pretty cheap parts. And while you are at it, double check the diode for the switch on the left ramp (orientation and if it is good.)

I will check the lamp diodes. I will also do the single lamp test to see if I have multiple issues going. As for the switch, I know the diode is good as I put in a new on with the new switch. At this point, the only think I can think of is damage to the wire itself that runs to the switch. The issue with BTTF is that the wire for that switch is not easily accessible...it runs underneath the ramp at the back of the playfield.
 
Yahtzee!

Once I mapped out all of the missing lights, it turned out I had an entire row out + two other lights. The row was actually due not to the row transistor but the diode connected to its base. Replacing that diode fixed the row. The remaining light issues were a bad bulb on one and a missing bulb diode on the other.

The switch issue was due to its wire having pulled out of the IDC connector under the playfield.

Now, the only remaining issues (none of which hamper playing) are:

1) 1 hard-to-get to bulb is out,
2) need to install my off-board battery pack,
3) low voice volume (need to order some caps for the sound pcb)
 
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