Re: Battlezone repair question

Well a normal functioning BZ board will not generate RAM tones unless it finds
one that does not pass it's test. The reason they tell you to check the RAM
at Nn is that the actual RAM test needs functioning RAM in order to work
properly. They are assuming that if your game is not working and no tones
are generated, then that first RAM must be bad. The problem is that, there
are lots of other reasons why the game may not get past the self test.

If your game is just dead (no sound, no video) then you have to basically start
troubleshooting the entire CPU circuit. A basic flowchart would be...

Verify Power Supplies
Verify Reset Line
Check Clock Lines
Look for 'constant' data or address lines (this takes experience)
Look for funny data buffers (LS245's)
Verify each address and data line between the CPU, buffers, High ROM and RAM.

the Self test can run with only the RAM, the uppermost ROM (addresswise) and
functional hardware (vector etc). Try taking out all unnecessary CPU ROM in case you have
a shorted address or data line on one of them. AFAIK, the self test screen will even come
up find if you take off the AUX board (but you will have a mathbox error).

Troubleshooting CPU problems can be tricky even with a lot of experience. That is why lots
of people around here are finding the Fluke/CAT/SA boxes extremely helpful. They will
eliminate many of the problems that are the most difficult to repair with just a logic
probe and a VOM! :-)

I think Nick Sayer had a Tempest troubleshooting page that sort of applies to BZ, the
theory is at least the same, none of the pinouts are tho.

jess

Joel Rosenzweig wrote:
>
> I've noticed that my Battlezone never generates the RAM tones in self test.
> The game seems to operate normally (for the time being!). I know that the
> docs say that if "no tones are generated during self test, check chip Nn"
> but I have a hard time believing that the game would otherwise function
> correctly if this chip were bad. Has this happened to anyone? I haven't
> yet setup my eprom programmer since I moved, otherwise I'd just program one
> and be done with it. I'm just curious, that's all.
>
> Anyone have a web page for some good procedures for debugging a BZ board? I
> have two boardsets that I'd like to get working again and I was defeated the
> last time I took up the effort about 3 years ago. I figure that maybe some
> people have learned a great deal about this beast since then that might have
> documented some really good methods for fixing this guy. The analog end of
> things are quite straight forward since it is relatively simple to follow
> the path of an analog signal. It's the digital side of things that gets
> hairy. For instance, when the CPU has a clock, and all address and data
> lines are pulsing, and each RAM chip is being selected at some point, as is
> each ROM, and the watchdog is barking, what's a good place to start? The
> watchdog is barking presumably because the CPU didn't write some data to the
> appropriate memory location in order to reset the timer. But, why? Memory
> access "appears" to be good. Anyway, it's this type of stuff that gets
> hairy, for me. What have some of you done when you run into this sort of
> road block? Replace all the RAM anyway? Then what?
>
> On another topic, anyone have an estimate for the price to produce a 2 sided
> PCB, same size as Battlezone's? Yes, I'm still thinking of laying out a PCB
> and populating it with new components. Unless the price is ridiculously
> expensive. It seems to me that making a new board would give reliability at
> least as good as they were originally, and with better components of today,
> the boards should run properly, longer - in theory. :-)
>
> Thanks,
> Joel-
>
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Received on Wed Jan 12 13:43:27 2000