Re: TECH: Help with collection of dead Tempest PCBs

I also usually ground out the watchdog as a first step
and see if there is any life to it.

--- Jess Askey <jess@askey.org> wrote:

> Here is my basic approach to fixing CPU/VG issues on
> Atari vectors... I
> will generalize and you can ask more specifics if
> you want... this
> process works pretty well for me...
>
> Firstly, if you have a 100% working boardset, you
> can use that to
> determine if the CPU or Mathbox PCB is bad on your
> non-working boards. I
> have never fried a working boardset with another
> non-working mate. Im
> sure others have but it is pretty damn rare. You
> might as well use that
> approach as the first step in a divide and conquer
> approach.
>
> 1. Resolder the interboard molex connector, suck off
> the old solder and
> get it fresh. You might want to do this on your 100%
> working boardset
> too because after yanking that connector off and on
> a few times, this
> could make your nice 100% board stop working too.
>
> 2. Power Supply... make sure the +5V is solid on
> both boards and you
> don't have an issue with burned connectors causing
> the issue. When
> testing on the bench, use a known good switching
> power supply. You can
> use the +12V for the 10.3 unregulated. You don't
> need the +/-22V for
> testing the CPU and Vector logic.
>
> 3. Can you run self test? Maybe it will just tell
> you what the problem is.
>
> 4. Check the clocks.... 50% of the Atari boards I
> fix are due to the
> crystals being broken since they stand up
> vertically, this was lovely
> when the PCB was safe in a cabinet but doesn't bode
> well when the PCB's
> are in a stack. I just make sure that the CPU clock
> is pulsing with a
> logic probe.
>
> 5. Check the reset line... it should pulse low and
> then stay high. If
> you dont' get a nice low blip on the logic probe,
> the CPUwon't start
> properly. If it doesn't act right, then check the
> power up circuitry
> which is related to the 10.3 unregulated voltage.
>
> 6. Start replacing all socketed chips from a known
> good board. Be
> careful when inserting chips as if you bend a pin,
> you will start
> causing more problems and destroying your nice spare
> working PCB. :-(
>
> 7. Probe the Address lines and Data lines, they
> should all be pulsing.
> If not and you have already replaced all the
> socketed chips, then
> suspect the LS245's and the RAM. Be careful pulling
> IC's out, if you
> start mangling traces, then again, you are moving
> backwards quickly.
> When in doubt, protect the PCB and sacrifice the IC
> since RAM and TTL
> are cheap. You can cut the pins off individually and
> then remove them
> one by one if you have a nice pair of tiny wire
> cutters.
>
> 8. Is the Reset line pulsing? If so, you have a
> barking watchdog...
> there is something wrong with the CPU that the
> programmers didn't plan
> on happening. You problem is most likely in the CPU
> section for Tempest.
>
> Those are my standard starting steps. From there, it
> gets a bit varied
> depending on what you find. :-)
>
> good luck
>
> jess
>
>
>
>
> Doug Hill wrote:
> > Hello gang.
> >
> > I have a tangential question for the vector list
> but I'm hoping you'll humor me. In restoring two
> Tempest games over the last year I now have a
> collection of Tempest PCBs that basically don't
> work. With the help of this list [and all the past
> posts] I now have two solid WG6100s to which I can
> attach these dead boards but I am at a loss as to
> where to start with the repairs on the game boards.
> >
> > When hooked up into one of the working cabinets
> most are just dead [no flashing start buttons, test
> switch does nothing, and obviously spot killer is
> on]. As far as I can tell the boards look complete
> [when compared to my two working board sets] and I
> have done the usual examination of the interconnect
> cable and the connectors on both PCBs.
> >
> > I've googled around quite a bit and almost all of
> the information online assumes the game PCBs are
> working and the WG6100 is the culprit - I now have
> the opposite situation. Is there any recommended
> reading as to where to start with these boards or do
> any of you guys have some places I should start?
> >
> > Thanks for any tips you may have and again my
> apologies for the slightly off-topic question...
> >
> > -doug
> >
> >
> >
> >
> >
>
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> >
>
>
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Received on Mon Jul 16 09:49:29 2007