Re: Tempest vector distortion

I finally got around to working on this problem.

I had just finished adjusting the size/position/dib pots on the Tempest
I'm fixing at home, so I did the same on the machine at work. In the
test mode, the vertical size was too large and the center was too high.
I re-adjusted the x and y size, position and dib pots, and the vector
folding problem went away.

I also adjusted the brightness and the faint retrace vectors went away.
The game here at work is working great, except for the buzzing spinner.
I'll fix that next.

___
Ken

On 08/09/11 17:46, Ken Sumrall wrote:
> I noticed someone had beaten the high score I had quickly put on the machine
> a few days ago, so I played 4 games and got 208K or so points. Not great, but
> I can't spend too much time playing it, because I have work to do. :-)
>
> I also used the opportunity to notice when the display was acting up. It seems
> to have problems with the levels that are not closed loops that are centered on
> the screen. The staircase, bowling alley, double U shape, and other similar
> levels seem to have a similar foldover issue like the TEMPEST logo, and it
> only starts once monsters are put on the play field. For the brief moment when
> the playfield is drawn and before it puts monsters on it, the display is fine.
>
> I'm thinking I should just change all 4 chassis deflection transistors. I have
> spares at home.
>
> I'll adjust the brightness too. Hopefully that will fix all the problems I'm
> seeing.
>
> I'll let you know in a few days once I've worked on it.
>
> ___
> Ken
>
>
> On 08/09/11 16:21, Andrew Welburn wrote:
>> If you turn up the brightness in the attract mode on the early revision you
>> can see the beam is sent way off the edges of the screen. Yes, they shipped it
>> like this. On a brand new monitor this was of little concern back in the day.
>>
>> Fast forward 30 years, and This either fritzes out the monitor completely or
>> causes foldover and other weirdness at several points including inter level
>> zooms and the firework display at the endgame. The deflection transistors can
>> cope with normal gameplay, but this over deflection causes partial saturation
>> of the transistor junction, and you see the weirdness with folding or curling.
>> Once the game returns to normal deflection size, the transistors behaves
>> normally.
>>
>> Either you change the game code and cross your fingers the monitor holds out a
>> bit longer, or you find the chassis mounted deflection transistor that is
>> breaking down under load and put in another.
>>
>> I have seen this folding/curling on 3or4 tempests in the past. Some people
>> don't notice it, think it's normal, or just live with it. Others like me want
>> to find out why and fix it :) it is common, and it's a problem that only shows
>> up on marginal monitors, it's easily fixed, but you need to swap out
>> transistors one at a time to locate the duffer. Because gameplay isn't
>> affected, some people leave it be, or can't understand why it happens. If you
>> study tempest on a scope display, you can see where the beam is allowed to
>> wander off to a maximum deflection position rather than be brought back to
>> rest at zero. The updated rom code addresses this lazy coding by adding return
>> to zero command every now and then on the fireworks, title screen and inter
>> level zooms... At least I think it does, I rarely find the updated roms on
>> tempest pcbs, it's super common to find the over deflecting romset all the
>> time. I don't remember which revision is which, suffice to say early revs over
>> defl
> ect, laters don't... There is paperwork from atari that describes what the new
> revision roms do, but I think the rom rev was only issued as an optional, not a
> compulsory upgrade, I think they mention something about 'extending the life of
> your monitor' with it.
>>
>> Andrew Welburn (mobile)
>> www.andys-arcade.com
>>
>> On 9 Aug 2011, at 23:53, Ken Sumrall<k_lists@scrapheap.net> wrote:
>>
>>> Really? They shipped the game with that error in the attract sequence? Or
>>> does it only happen on monitors that are marginal?
>>>
>>> I did notice what I thought was an odd EPROM configuration. There are only
>>> 3 EPROMs on the board. 2 are over by themselves, away from the CPU. Then
>>> there is an EPROM in a socket near the CPU with some wires running from it
>>> to various points on the board, and written on the label it says something
>>> like "Tempest 256K ROM". Is this a known hack to put most of the game in
>>> a single ROM? Should I just burn a new set of ROMs of the final version of
>>> the code?
>>>
>>> I'll get video of the curved vector lines and also of the EPROMs on
>>> the board and post them. Probably sometime tomorrow.
>>>
>>> ___
>>> Ken
>>>
>>>
>>> On 08/09/11 15:30, Malcolm Mackenzie wrote:
>>>> The foldover at the end of the attract sequence is a code error in early
>>>> revisions of the game.
>>>>
>>>> The faint lines you're seeing are indeed retrace lines. Adjusting the
>>>> brightness
>>>> should fix that. If not, you may have a problem in the z amp section of the
>>>> monitor or board.
>>>>
>>>> The curving lines are a bit of a mystery...
>>>>
>>>> --- On *Tue, 8/9/11, Ken Sumrall /<k_lists@scrapheap.net>/* wrote:
>>>>
>>>>
>>>> From: Ken Sumrall<k_lists@scrapheap.net>
>>>> Subject: VECTOR: Tempest vector distortion
>>>> To: "vectorlist@vectorlist.org"<vectorlist@vectorlist.org>
>>>> Date: Tuesday, August 9, 2011, 3:14 PM
>>>>
>>>> Hello,
>>>>
>>>> We have a small arcade at work, and I recently got the cabaret Tempest machine
>>>> there to work again. Basically I just pulled the logic board and reseated all
>>>> the socketed chips and the interboard connector cable.
>>>>
>>>> It now comes up, stays up, and shaking the cabinet doesn't cause the game to
>>>> crash. However, I'm seeing some vector distortion. When it displays the
>>>> TEMPEST logo in the attract mode mode, near the end of the animation, the
>>>> vectors foldover, and then (mostly) return to normal. You can see a video
>>>> of it here:
>>>>
>>>> http://www.scrapheap.net/tempest/
>>>>
>>>> Also, on some levels (in particular, the one I call the staircase level)
>>>> straight lines get drawn with a definite curve in them, and the screen tends
>>>> to pulsate a bit with the size of the image growing larger and smaller. My
>>>> first reaction is I need to work on the monitor, but then I thought maybe I
>>>> need to adjust the X and Y size and position pots on the logic board.
>>>>
>>>> I also see some faint lines which I assume are the beam location being moved
>>>> with the beam turned off. I assume I fix this by adjusting the screen
>>>> brightness.
>>>>
>>>> Suggestions anyone?
>>>>
>>>> Thanks in advance for your help!
>>>>
>>>> ___
>>>> Ken
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>>>>
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Received on Thu Aug 25 03:32:05 2011