Re: Lunar Lander help

I had an AD561 and TL082 available, so I first replaced the x-axis AD561 and
the problem was still there. Then I replaced the x-axis TL082 and the
problem was still there. Because I had no 4016's available, I decided to
try an experiment to determine if the x-axis 4016 chip was at least faulty.
I removed both 4016's (socketed them) and swapped them around to see if the
problem would follow the chip. This time, video display looked normal.
However, given my tendency to like proof, I swapped the chips back to their
original spots and tested it again. The video was _still_ normal.

As I described in the original post, this problem comes and goes. It took a
while to witness the problem on a scope, because the first few times I did
this, the problem would go away, and stay that way even after the scope was
removed. Then weeks later, I'd start the game up again, and it was pot luck
whether or not the display would be normal or not. Given that the problem
was still there prior to swapping the 4016's with each other, I have to
believe the real problem is still there, and it will show up again soon.
I'll have to keep an eye on it, and I might as well order some new 4016's to
replace the originals anyway, though I know those aren't the problem.

I'm still wondering about the self test. Does anyone know if LL self test
is supposed to generate any video? And is freeze spray or the frost
conductive, or can we spray it till our hearts content without fear of
shorting out any components?

Regards,
Joel-

----- Original Message -----
From: <ygroups@andora.org.uk>
To: <vectorlist@synthcom.com>
Sent: Sunday, June 22, 2003 8:29 AM
Subject: Re: VECTOR: Lunar Lander help

> Hi Marc,
>
> Although I don't know much about the Lunar Lander per-se: I am familiar
> with other Atari Vector generator circuits. After guessing that these
> items are in the post-DAC analog output section, I just wondered why
> changing these particular ICs would affect the Self-Test pattern and not
> the main Game signals, since both modes of operation use the DAC sections
> and only the self-test seems to be the problem? Afterall, Joel stated that
> the problem he has is a blank-self-test screen, but the game plays ok
> otherwise !
>
> If these items are in fact in the Z-Brightness part then I see what you
> are getting at.
>
> If not, I would suspect the Z output section and any signals which affect
> this circuit in self-test mode. Or may be the PROM (EPROM) with the
> self-test code in it.
>
> Just a few thoughts - cheers - Tim.
>
>
>
>
>
> "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 07:23:13 2003