Dig Dug Help

khite

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I received a free Dig Dug arcade game the other month from a friend that was going to toss it. I am working on getting back up and running in order to give to my father for Christmas! The issue at hand is that when turned on, the coin door and Marquee light up. The monitor also seems to be doing something since a nice high pitch hum starts with the machine as well. The first thing I did was cleaned out the machine from the dust and stink bugs. Then I replaced Big Blue and I am stuck now. I have tested all the outputs from the power supply and get the voltage within tolerance. Below are the test points and voltages I recieve:

P5:
Pin 1,2,3-4,5=14.93VDC
6-7=38.2VAC
8-9=6.6VAC
10-12=64.5VAC
13-15=64.7VAC

P7:
Pin 5,6-1,4=5.19VDC

So the issue I am at is when I test the +5V on the game board, I get .65V but there is +5V coming off the A/R II as I tested the voltage off the plug itself as well.

Any and all help is appreciated.
 
All of your transformer block & ARII outputs look normal to me.

If you have +5VDC at P7 (output of ARII) but don't have it on the game PCB, then I'd consider two possiblities:

1) A problem with the harness/connectors.
2) A short on the PCB.

Unplug the big edge connector from the game PCB, check for +5V there (2/B relative to 1/A). While you're there probing, examine the pins and connector housing. Look for burns, pins that have been bent badly, etc.

IFF you've got a good 5VDC on the edge connector, and it's in good shape... but it pulls down to 0.6V with the PCB plugged in... then it's time to look for the short on the PCB.
 
All of your transformer block & ARII outputs look normal to me.

If you have +5VDC at P7 (output of ARII) but don't have it on the game PCB, then I'd consider two possiblities:

1) A problem with the harness/connectors.
2) A short on the PCB.

Unplug the big edge connector from the game PCB, check for +5V there (2/B relative to 1/A). While you're there probing, examine the pins and connector housing. Look for burns, pins that have been bent badly, etc.

IFF you've got a good 5VDC on the edge connector, and it's in good shape... but it pulls down to 0.6V with the PCB plugged in... then it's time to look for the short on the PCB.

I usually will ohm out the +5v input to the board to check for a short. In this case I believe it to be 1,A,2,B for the +5 and ground. If there is a short on the board you should see a low ohm reading. This is a quick and easy test (with power off) and it will let you know in short order if there is a problem with the main board.
 
Thank you for the responses

DarrenF: There was 4.99V on the bid edge connector. Everything looks ok, no obvious burns or bent pins.

kb0jjn: When you saw low, how low are we talking? I read
1A:78.1 Ohms
2B: 77.1 Ohms
Both respective to their proper locations

Is that low enough, or are you talking like a few ohms low?
 
That seems too low to me. You should be measuring each + pin to ground and there should be higher resistance than that (usually in the k ohm or close to it). I'll have to check mine and let you know what I have.
 
Ok sorry for the long delay. School had to take first priority for quite awhile. But now I am back to the Dig Dug machine. So below are the different measurements I took. I wrote these in my log book awhile ago and just took them.

Voltages on Game Board Connector (Volts):
2-1:3.99
2-A:4
B-1:4.03
B-A:4.03

Resistance on Game Board(Ohms):
2-1:76.7
2-A:80.2
2-Gnd Lug:80
2-Z:77
B-1:77.3
B-A:77.3
B-Gnd Lug:79.9
B-Z:77.3
+5V Lug-1:79.5
+5V Lug-A:79.5
+5V Lug-Gnd Lug:78.8


I also measured the +5V lug voltage and received .653 Volts. So does this still look like a short on the game board?
 
Randy Fromm had a trick for finding that in an old video of his. The Dig Dug board has the chips arranged in a row. The upper part was the + and the lower part was the -. He took the board out, put the leads on the board so he could read the voltage across the rails.

The board would read lower and lower as you got closer to the short, and it would show nearly the exact location/chip that was shorted by doing that.

This trick was done a LONG time ago on those old boards made in the late 70's and early 80's like yours. He posted these old videos on youtube now, so you can see it in the above link at about 3:20 into the video. If you do that, you might find the voltage dropping to nearly 0 by the bad chip.

http://www.youtube.com/watch?v=RH-ms1JKAxs

This is when Randy was young...and the video games were new.
 
Ok so I was wiggling the connector in and out a little, and a few things happened.
-The red LED turned on
-Some noise with the speakers.

And then I slipped a blew a fuse. So tomorrow I will be replacing the fuse and continuing the troubleshooting. Anybody have any ideas on what to help the connection?
 
Looking at my Dig Dug and the schematics, I think I have a diffrent board. Also look at the pics I have uploaded. The customs (07xx) have tarnished legs and these are a clock type. Most of the pins on these chips should be flasing your logic probe. I have several of these that are bad (from another game). The chips with the tarnished legs should be cleaned and re seated.

Also test your voltage at the connector and again at the chips.

My problem is the schematics are not the same as my board.

Notice in the first pic the A is a +5 voltage of some kind and Z is ground. On my bord they are connected so that will NOT work for me. My board is a Dig Dug 2 board and not sure what that means but I would bet the pin outs are diffrent.
 

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Looking at my Dig Dug and the schematics, I think I have a diffrent board.

My problem is the schematics are not the same as my board.

Notice in the first pic the A is a +5 voltage of some kind and Z is ground. On my bord they are connected so that will NOT work for me. My board is a Dig Dug 2 board and not sure what that means but I would bet the pin outs are diffrent.

Pin A is labeled "5V RTN". RTN as in RETURN. This IS a ground connection. Pin 1 is also a "5V RTN" (aka ground). Your +5V is on 2, B & Y.

I think your PCB matches the schematics just fine.
 
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Pin A is labeled "5V RTN". RTN as in RETURN. This IS a ground connection. Pin 1 is also a "5V RTN" (ak ground). You +5V is on 2, B & Y.

I think your PCB matches the schematics just fine.

In addition, Z is ground and tied directly to A by the trace. (which matches your scat)

Yes, there are 2 different revs and 2 different types of this board just to make it more confusing.
 
I look into my board today and did not find much going on. Nothing on the data lines and cpu's doing stupid stuff. There was a loud wail on the audio out. As I was probing the z80 main processor chips my hand hit a HOT chip. This chip would burn you! I lowered my voltage to about 4.84v and put power to the board and soon the chip got really hot. I removed the thing before it caused a fire.

This chip is at location 4 k or L (going from memory and like eyes going bad). This is a AM9148-55DC and I am having trouble finding the data sheet for this.

After I pulled the fire hazard chip I felt around for more hot chips and found on other. It was a TM or TMM chip, the same one's that are on the Galaga video board. I have a few for testing and put a newer one in there and it stayed cool.

The z80 chips were still mucked up and doing strange things. I replaced every one and now the board has lots of signs of life. It is still missing the one chip and I'll be looking to replace that (AM9148-55DC).
 
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