Re: Tech: Tempest (not)reset line & WD

Hi Mark. Thanks for the info. Are the (not)reset circuit and the watchdog
circuit the same thing? Looking at the schematics I can't figure out where
the output is located, or the input for that matter. The game does not play,
there is no self-test or picture, the player select button LEDs do not light
up, and the (not)reset signal works except for a section of the circuit that
is dead. To be specific, pins 9 and 15 of E4, pins 12 and 13 of E3, and pin
3 of D3 are all pulsing with the WD grounded. Other than that, the signal
works fine in the other sections of the circuit.

I've still got alot to learn, but I want to see if I can repair this myself.
Basically, I looked over the schematics and pinpointed every place that was
labeled as (not)reset. From what I could tell, this included the
aforementioned chips along with A4, pin V of the Main edge conn., pin F of
the Aux edge conn., and and J3 and H4 on the Aux board. I replaced all the
chips and checked all the traces but nothing has changed. I'm baffled!

Any ideas? Thanks again!

Roger

>From: Mark Shostak <xx.vl@cinelabs.com>
>Reply-To: vectorlist@vectorlist.org
>To: vectorlist@vectorlist.org
>Subject: Re: VECTOR: Tech: Tempest (not)reset line & WD
>Date: Thu, 1 Apr 2004 22:35:23 -0600
>
>Roger,
>
>On Thu, Apr 01, 2004 at 10:03:11PM -0600, Roger Smith wrote:
> > Around what voltage level should the (not)reset line be at normally and
>when
> > the reset button is pressed?
>
>When reset is pressed, the !reset signal should be close to (not)zero
>volts.
>Technically, anything <.75V is fine. When the button is released and
>everything
>is working, !reset should be close to 5V.
>
> > Also, I am trying to figure out how to use the disabled watchdog as a
>tool
> > when troubleshooting. When I'm looking at the faulty (not)reset circuit
>with
> > my logic probe, and the WD is NOT grounded, the entire circuit is
>barking.
>
>Sounds good.
>
> > When the WD IS grounded, the circuit is at the correct logic levels for
>the
> > most part, with only a small area barking. If I understand correctly,
> > grounding the WD makes the program run properly for the sake of
>
>Not exactly. Grounding the WD disable signal only stops the watchdog from
>reseting the CPU and the reset of the board (VSM, etc.). It can't make the
>program run properly, if, say, you have a bad ram, or a bad rom.
>
> > troubleshooting, so I'm guessing the area that is still barking even
>with
> > the WD disabled is the faulty part of the circuit.
>
>I'm not sure what you mean by "area". The only area of the WD circuit you
>should care about, is the output, and to a lesser extent, the input.
>
> > Am I interpreting this correctly? If not, could someone please clear
>this
> > up for me? Thanks.
>
>Not sure what your actual symptoms are (other than a pulsing reset line).
>Have you checked your ram?
>Have you checked your rom?
>RAM is a common failure, and the cheap sockets on that board give
>intermittent rom failures.
>Of course, be sure to reflow the cracked solder joints on the mathbox
>harness (both ends).
>Does it self test?
>Any picture?
>
>A pulsing watchdog is a common symptom. Search the archives at
>vectorlist.org.
>
> > Roger
>
>-Mark
>
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Received on Fri Apr 2 20:45:13 2004