Re: Lunar Lander help

Actually, re-reading Joels post I would be inclined to think that Marc is
correct and the post-dac and/or the DACs might be a problem. The
non-linearaities would suggest one section is failing and since the
problem comes and goes with a scope connection, maybe there is a joint
problem.

But why no self-test cross-hatch?

"Marc Alexander" <marcwolf123@yahoo.com>
Sent by: owner-vectorlist@synthcom.com
20/06/03 05:19
Please respond to vectorlist
 
        To: <vectorlist@synthcom.com>
        cc: <joel.rosenzweig@verizon.net>
        Subject: Re: VECTOR: Lunar Lander help

Hi Joel,

If you'd like to save yourself some trouble and time, apart
from visually inspecting that all the parts in the video output section
are there and intact,

Remove:
    4016 @ D12
    4016 @ B12
    TL082 @ C12
    TL082 @ A12

Replace the locations with good quality IC sockets, preferably 'machined'
ones,
after checking that all the track and pads are clean and intact,
(you'll need 2 x 14 pin and 2 x 8 pin machined IC sockets)
and put in new 4016's and TL082's. They are cheap and easy to get, and one
of
them is most likely the problem.
It may also be one of the AD561 DAC's but they are much harder and more
expensive to get, so you may as well do a nice replacement job on the
easier and more likely problem area first.

If you don't have a desolderer you can use pointy snippers to cut the legs
of the
IC's carefully one by one at the body, then use an iron and tweezers to
remove each
leg one at a time, then use good quality desolder-wick on the pads.

Anyway I hope this helps!

Best regards,

Marc

----- Original Message -----
From: "Joel Rosenzweig" <joel.rosenzweig@verizon.net>
To: <vectorlist@synthcom.com>
Sent: Friday, June 20, 2003 1:26 PM
Subject: VECTOR: Lunar Lander help

> Anyone know what the Lunar Lander self test is supposed to do with
respect
> to a video display? My LL displays an image and plays in the normal
game
> mode, but doesn't display anything in the self test. Switches on the
> control panel do activate sounds during self test though. I assumed
that
> the self test would behave similar to Asteroids so that I could see a
cross
> hatch style pattern on screen. Is LL self test supposed to be blind?
>
> I wanted to see a cross hatch pattern so that I could more clearly
identify
> the problem I'm having with the video output. Basically, there's a
vertical
> column of video, about 2-3 inches wide that spans the entire height of
the
> display, starting at the left edge of the 4 digit score, fuel counters,
> extending to the right. Video objects that are in this column get
totally
> distorted, almost as if stretched fully between the left and right
edges.
> Then, once the object passes out of this column, it regains its shape,
and
> looks normal again. The lunar terrain that occupies the space below
turns
> into a broken line that stretches from side to side. I'll have to take
a
> picture to give you a better description. It's really odd looking.
>
> When I hook up a scope, the problem usually goes away! Hah. I finally
> caught the problem on the scope, i.e. it's not a monitor defect. I've
> noticed that the problem comes and goes, and has no relation to being
first
> powered on, or having the machine sit powered on for a while. The
problem
> essentially "drifts" in and out slowly. Given the drifting, it has a
real
> analog feel to it, like a bad cap somewhere, but I haven't gotten to the
> point where I've located a candidate. I'm not convinced a cap could
even do
> this. I scoped the inputs to the DAC while having the problem, and the
> inputs are all toggling. That in itself isn't a proof that the inbound
> digital data is sane, but at least no inputs are stuck.
>
> I'd certainly enjoy hearing any suggestions for what to look at. I'll
try
> to study the schematics some more, too. And if you think a picture
might
> help out or at least entertain you, I'll take one tomorrow and post it.
>
> Regards,
> Joel-
>
>
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Received on Sun Jun 22 05:37:05 2003