Re: black widow pcb problem no play no picture clock working

  Ok, nobody replied to that last one. I must have made it too confusing.
Well Tony Jones told me to remove the CPU and check to see if the clock
and the reset are working. I checked with the logic probe and I get
pulsing from the clock. So I assume thats working. I checked the reset
signal lines and their at a constant low state. There are lines from
counters E4 and F4 that go to F7 (74LS14) that are marked POR(power on
reset)on the schematic. Those lines are at a constant high state.
Can anyone tell me what the reset should be doing?
The only thing on this board that seems to be doing anything is the
clock. Everthing else is either at a constant high or a constant low
I am not familiar with how the watchdog works or the power on reset for
that matter. I assume that the watchdog comes on whenever there is a
problem on the board and stops anything else from being damaged (like
the monitor).
If I disable the watchdog, by putting the WDDIS test point to ground,
will that hurt anything? Will it get the game running again so I can see
whats going on?
Or is that not the right direction to go in?
I wish someone would put out an atari vector pcb repair and
toubleshooting FAQ.
I looked through the vector list archive and I have found nothing that
could help me.
I can stare at this schematic all day long and not make heads or tails
of whats going on.
I have no idea what test signals I should be getting with the logic probe.
Well if someone could give me a little info I would appreciate it.
I sure need it
Dan Piraino

Daniel Piraino wrote:

> Checked clock and reset signal
>
> I removed the CPU
>
> I probed the clock and it is pulsing normally all the way up to pin 5
> of E4 counter(74LS193).
>
> The POR is high when it exits pin 14 of E4 counter (74LS193) and pins
> 2 and 12 of F4 counter (74LS393) and enters F7 (74LS14) at pins 4 and 5.
>
> But once it exits F7 (74LS14) at pin 3 and 6. It becomes low where it
> goes out to R8 (TL082), E3 (74LS00), K3 (74LS74) and the POR test
> point. It remains low from pin 4 of R8 (TL082) out to the reset.
>
> pin 3 of E3 (74LS00) goes out high to H4 counter (74LS393), as it
> exits pins 6 and 13 of H4 counter (74LS393) it goes low out to K3
> (74LS74) and F4 counter (74LS393).
>
> Pin 9 of L4 (74LS08) is high out to the WDDIS test point. Pins 8 and
> 10 of L4 (74LS08) are low.
>
> Well I hope thats understandable. Its the only way for me to describe
> whats happening,
>
> Hope someone can help
> Thanks,
> Dan Piraino
>
> -----Original Message-----
> From: Daniel Piraino <dpiraino@twcny.rr.com>
> To: vectorlist@vectorlist.org
> Date: Tue, 02 Aug 2005 23:49:32 -0400
> Subject: Re: VECTOR: black widow xy monitor problem
>
>>
>> The reset tests low with the logic probe
>> Thanks,
>> Dan Piraino
>>
>> Daniel Piraino wrote:
>>
>> > The board set is not working
>
>
> get the schematics from the web.
> use the logic probe to check the clock and reset signal.
> i know you said it is low, but check it from end-to-end.
> if the clock seems dead from the begining then replace the crystal.
>
> once the clock and reset are good we can move forward.
>
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Received on Fri Aug 5 18:16:28 2005