Midway Seawolf board repair

[Brad]

My Seawolf board set developed a problem the other day and I have not been able to figure it out. Although, I am finally learning more about running by oscilloscope. If anyone has a working one or knows how to fix these that would be great. I have three sets of the mother/daughter board.

Thanks!

Brad

[John Robertson]

Hi Brad,

If you remove the Boot PROM (H1 if I ;m not mistaken) you should see
parallel lines on the screen. If you then press the slam switch on the
coin door these should alternate.

There is documentation on the RAM test (what you would be doing),
showing which line corresponds to which RAM IC - you just have to hunt
for it a bit, and I'm not at the shop so can't tell you more at the
moment. I don't work on those boards very often, and when I do I have
more powerful tools (Fluke 9010 and 8080 pod) at my disposal so don't
use the built-in RAM test.

John :-#)#

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[Brad]

John

Midway put out a book of "Standardized Test Procedure for Midway's Processor Boards" (you probably have seen it). I have been trying to work with that, but I am not skilled at all in using the oscilloscope so it has been difficult. Anyway, this past weekend, I pulled the proms out and hit the slam and I got vertical lines, but they were not like what was described in the book. Actually, the lines were there before I hit the slam switch so hitting it had no effect. The lines where just continuous lines that did not have the pattern described in the book. Looked like: IIIIIIIIIIII not III I III I III I III I, so it did not seem very helpful. I tried the other two sets of boards I had and those did not show anything with the proms out. I am not sure where to go from here so any help is appreciated.

Thank you,

Brad

[John Robertson]

Hi Brad,

Trying to fix those boards with a scope is an exercise in futility.

Really.

You need tools like a good Logic Probe (I really prefer the classic
Heathkit as the best one), Fluke 9010 with the 8080 pod, and possibly a
Chip Comparator.

The scope is useful for seeing repetative things, noise, audio, and RF
signals, but I've not found it a heck of a lot of use in board repairs
other than working on clock circuits and vector drawing issues. Others
may differ, but then again I run a shop and have to be efficient (OK,
-I- have to be efficient) on board repairs because I have so little time
to spend on the bench these days.

I have no idea where you live, but perhaps you are close to a collector
of arcade test equipment who has a 9010 & 8080 pod and will let you play
with them...

I do recall that the RAM test, which you appear to be in, should show a
series of vertical lines, equally spaced - some fat, some thing, and
they should alternate when you operate the SLAM (Reset) switch.

So I'd start with tracing the SLAM switch to see if the CPU actually
gets a reset (reset low I think for the 8080(?)) or not. If not then fix
the reset circuit and try again.

[arcade player # 2]

Id just send him the board and let him fix it,the pop a beer or two and wait a couple of weeks until it shows up..

[Brad]

John,

Funny thing I forgot about. When I got into collecting arcades (little more than a decade ago) my Dad purchased an 9010 with the 8080. I do not think I ever got around to turning it on and then I forgot about it. But, I gave him a call and sure enough he still has it sitting in his basement. I will pick it up and play with it this weekend.

I did some testing with a logic probe last weekend and that I at least could understand what was going on. The scope I had not gotten very far with, but I figured that was the thing I needed. It is a relief to know that I have a better option available. I will let you know if I figure anything out.

Thanks a bunch!!

Brad

[John Robertson]

If you go to my tech tools maillist archive you can read conversations
about using the 9010 and 8080...

Archive site: http://seven.pairlist.net/pipermail/techtoolslist/

[Brad]

John do you know how the tilt wiring works on Seawolf? I was trying to verify that the board gets a signal from the switch, but on the schematic the switch is wired to a ground and then it goes to the power supply not the game board. So I am not sure how to verify that it is getting a signal. There was continuity from the ground through the switch and to the power supply.

Appreciate any help!

Brad

[Brad]

Also, the pod I have for the 9010 is a z80 so if you know anyone that has a 8080 they were willing to part with for a reasonable price I would be interested in purchasing it.

Thanks,

Brad