Re: Tempest resetting problem

Woah dude! You are getting in deep. I'd love to work out a program for the Fluke
to test these board sets, but I have to handle the Asteroids problem still
....<must stay focused, grunt!... must not pay any attention to problems of
others....>. Wait a moment, it may be the same basic problem; the Watchdog reset
is going off, and the circuitry to it is fine. Let's start with your RAM
question. I wonder if, as on my Asteriods board, you will hear the beeps when a
RAM is bad once the game is set to test mode. Try pulling a RAM, putting the test
switch on, and seeing if the board ID's the bad (missing) RAM. Then you'll get an
idea if the RAM's can be detected as OK or not.

On my board, I am convinced that the watchdog is allowed to go off because the
vector generator circuit is not sending back the "Vector Done" signal to the 7442
(?!? man, I haven't got my manuals dude, I have to look that chip up) Basically,
if you hold this signal high, you'll find that the board stops resetting,
indicating that the handshake betweent the CPU and the vector logic is broxed.

I'll try to look at the schematics tonight and see if I can't recall what notes I
had written there on this one.

Ace

Matt Rossiter - Verio Southern California wrote:

> Let me add one thing to this post. When I pull out the 122 ROM (Rom 8 at
> R1) - the resetting completely stops. When I put the Rom back in it beeps
> and flashes. I know the ROM is Ok because I pulled another one out of a
> working tempest board. I'm wondering if the CPU is having a hard time
> executing the first instruction or something? Maybe its first instruction
> is to write something to memory and can't?
>
> ....why am I up at 3:50am?
>
> going nuts.
>
> matt
>
> _____________________________________________________________________
>
> On Tue, 19 Oct 1999, Matt Rossiter - Verio Southern California wrote:
>
> > Well, I've ruled out the Power Reset and Watchdog counter along with the
> > clock circuit. I used a logic comparator and tested every chip in that
> > circuit and they all test out fine.
> >
> > My roomate seems to disagree with my "it's a ram problem" theory because
> > if the CPU keeps resetting it will never see the ram.
> >
> > I do have a question though. There are 4 2114 ram chips which make up the
> > program ram and about 6 which make up the vector ram. Right? Well, I
> > tried pulling out the roms as suggested below and looked at the chip
> > select pins on the ram chips. All the program ram chips stayed high while
> > all the vector ram chips were pulsing on the chip select line. In fact,
> > they pulsed at about the same frequency as the reset line pulsed. Could
> > there be a clue here? hmmm....
> >
> > By the way - I ordered some of those Braemar tapes for the Fluke 9010a
> > troubleshooter and they are $16 bucks a piece (yes I also know how to use
> > the RS232 interface) and they only sell them in packs of 10. I got them
> > anyway - don't ask me why. Well, whoever can give me a solution that
> > works for this tempest problem will get a free blank tape on me! Oooh
> > Ahhh! You don't even have to pay for shipping.
> >
> >
> > Matt
> >
> >
> >
> >
> > _____________________________________________________________________
> >
> > On Mon, 18 Oct 1999, Chris Loggans wrote:
> >
> > > > ...
> > > >2) I'm not so sure of the ram. My fluke 9010a can't do a read/Write to
> > > >anything in the ram address space (both program ram and color vector
> > > >ram) - so either one of the buffers is bad or a ram chip is bad.
> > >
> > > I think this is your best guess right here. If the Fluke cannot reach the
> > > RAM, then the CPU can't reach the RAM and nothing will work. As you
> > > mentioned, it could be a buffer issue. It could also be a chip select
> > > issue. If this is the case, then either the chip select lines are not
> > > functioning or there is a chip that is stuck "on", regardless of whether or
> > > not is is selected. Even though you know the ROM's are OK, I would remove
> > > all of the ROM's and then try to do the RAM test. If the RAM can now be
> > > reached, then put the ROM's back in one at a time and see when the problem
> > > re-occurs. You should be able to narrow it down from there.
> > >
> > > Good luck,
> > > -Chris
> > >
> >
> >

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