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How to repair a CX-75 LightPen?

LightPen CX-75 repair

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#26 luckybuck OFFLINE  

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Posted Fri Apr 19, 2019 11:40 AM

Thanks Doctor, we tested with an Atari 130 XE in port 2. Sadly, with the same results. Further, we have used crt TV. Will try another approach at the next meeting. BTW, port 4 of the Atari 400 should work, if I have understood correctly.



#27 luckybuck OFFLINE  

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Posted Fri Apr 19, 2019 11:42 AM

Thanks Allan,

 

Well, who knows? More and more mystery stuff is coming to the light, thanks to the users here. :-)



#28 _The Doctor__ OFFLINE  

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Posted Fri Apr 19, 2019 12:05 PM

Time for a user made light pen repair tutorial ;)



#29 luckybuck OFFLINE  

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Posted Fri Apr 19, 2019 12:23 PM

:-) Yes. :-)

 

But first, we will publish on how to r/w with 6,000 baud on and from a cassette recorder... Breakthrough was made again at the NOMAM meeting last week. Meaning transfer rates more than 10 times as in the golden age...



#30 Mathy ONLINE  

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Posted Fri Apr 19, 2019 12:45 PM

Hello luckybuck

 

As far as I know, it wasn't SALT, but a piece of software especially written for testing stuff that plugs into the joystick port.  I probably downloaded it recently from AtariAge and it's name might have been "Periphery tester".

 

Sincerely

 

Mathy



#31 luckybuck OFFLINE  

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Posted Fri Apr 19, 2019 12:52 PM

Yes, you are right, but SALT has a LP test at least, but not the good one, you have used with coordinates. :-)

 

Attached Thumbnails

  • SALT20.7-1.jpg
  • SALT20.7-2.jpg


#32 CharlieChaplin OFFLINE  

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Posted Sat Apr 20, 2019 5:01 PM

Hello luckybuck

 

As far as I know, it wasn't SALT, but a piece of software especially written for testing stuff that plugs into the joystick port.  I probably downloaded it recently from AtariAge and it's name might have been "Periphery tester".

 

Sincerely

 

Mathy

 

Peripheral Test by Florian Dingler ?!? Attached here as HWTEST.ATR + several other test programs and drivers for various controllers and peripherals... (including Lightgun and Lightpen).

 

The only problem I ever had with a lightpen was, that it was broken right in the middle when it reached my door... (ordered from Video61 and kindly replaced by Lance). The lightpen seems to have an inverted trigger compared to the lightgun...

 

If you use a lightpen with lightgun games, in several of these games you will notice fast autofire (like a machine gun) when you actually do NOT press the lightpen trigger; play Bug Hunt, Crossbow. Barnyard Blaster, Operation Blood LG, Special Forces LG, Sharp Shooter ,etc. and you only have to hold/point the lightpen in the direction where you want to shoot (+- several centimeters or decimeters of in-accuracy to the left/right which is typical for a lightpen) and fire dozens or hundreds of shots per minute. If you have infinite ammo, this is good, otherwise you will be out of ammo soon. And errm, games that look how effective you are and give a rating (number of shots fired vs. number of shots hit = percentage of effectivity) will mostly end with very low rating (Bug Hunt, Barnyard Blaster, Sharp Shooter, etc.). But maybe you just want to learn writing the ABC (upper+lower case) with a lightpen and Letter Tutor...?!? ;-)

Attached Files


Edited by CharlieChaplin, Sat Apr 20, 2019 5:08 PM.


#33 luckybuck OFFLINE  

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Posted Sat Apr 20, 2019 5:08 PM

Thanks CharlieChaplin, will try it at the next meeting. :-)

 

Happy Easter!



#34 CharlieChaplin OFFLINE  

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Posted Sat Apr 20, 2019 5:22 PM

Thought that either "Die Fundgrube" or "Die Trickkiste" contains instructions and schematics how to build your own lightpen, but when I just looked, I could not find it. So it must have been a similar german book (there was one in A4 size, full of photocopies, made by an Atari club from Duesseldorf, maybe this is the one)...


Edited by CharlieChaplin, Sat Apr 20, 2019 5:30 PM.


#35 luckybuck OFFLINE  

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Posted Sat Apr 20, 2019 5:26 PM

Thank you so much. Did bought them in the 80's, but totally forgot. :-)



#36 Nezgar ONLINE  

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Posted Sat Apr 20, 2019 9:45 PM

I wrote my own light gun program in BASIC way back, using the PENV and PENH PEEK locations. I recall a black background, or even dark was not enough for an accurate position. To 'draw' it's best to set the background to all white so the pen/gun can sense the light the best.

Games like bug hunt and barnyard blaster will 'flash' the screen all white for 1 scan of the screen to help the light gun for 1 frame. It also is quite tolerable along with a gunshot sound. :)

So poke 710 and 712 to 15, and 709 to 4 or so and peek PENV and PENH

I'm also wondering if the behaviour may be different for PAL and NTSC?

#37 luckybuck OFFLINE  

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Posted Sun Apr 21, 2019 5:02 AM

Thanks Nezgar,

 

That is a good point. I will try this at the next meeting. With all the combined help, I am sure, we will gonna make it. :-)

 

Happy Easter to all.



#38 Rybags OFFLINE  

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Posted Sun Apr 21, 2019 6:03 AM

The light gun positions returned correspond to VCOUNT values for vertical which align properly with PAL/NTSC insofar as the 240 scanlines you can control via a display list, so no program changes required.

 

PAL will allow ranges extra to what NTSC can do due to the extra 50 scanlines generated - usually though the extra scanlines are black since it's usually impossible to control colour outside the 240 scanline area.

 

But using the scanline 240 bug you can obtain colour control and even display PM graphics in the extra display area though for most NTSC TVs you'll not be able to see it.



#39 luckybuck OFFLINE  

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Posted Sun Apr 21, 2019 5:58 PM

Thanks Rybags,

 

What frustrated is, that we used the AtariGraphics cart from 1984, especially made for the light pen. But it failed even there... :-(

 

Next meeting, same player tries again. ;-)



#40 BigO OFFLINE  

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Posted Mon Apr 22, 2019 7:50 AM

So, to recap, we're still not sure whether the light pen is broken or not.



#41 Mclaneinc OFFLINE  

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Posted Mon Apr 22, 2019 8:10 AM

Lol......Seems not...I personally think it is (broken) and a simple replacement of the photo sensor would mostly prove this in a cheap way..I can't image an IC and transistor being overly expensive either.

 

It still stuns me that people have a real crt to test this all on...


Edited by Mclaneinc, Mon Apr 22, 2019 8:45 AM.


#42 BigO OFFLINE  

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Posted Mon Apr 22, 2019 9:05 AM

Having no expertise in the matter, I tend to agree that it's broken.

 

I still don't understand what was meant when it was said that it worked in one axis but not the other. That's what got my attention as I wanted to understand how the light pen could detect an axis in any way.

 

Still interested in the outcome and hope that some documentation of it's design and/or functionality come out of this exercise. Never can tell when I might own one of these things. And if I own it, you can bet it was cheap enough that it's probably broken. :D



#43 luckybuck OFFLINE  

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Posted Mon Apr 22, 2019 10:04 AM

@Mclaneinc: '...replacement of the photo sensor...' ist not the problem, the problem is to disassemble the pen without visual damage afterwards...

 

Sure, we keep the crt TVs in order to play some games with the light gun and showing the following generations what was possible in those times with the light pen.

 

Wasn't there even a show with Andy Warhol showing what the Atari can do in arts? ;-)



#44 Mathy ONLINE  

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Posted Mon Apr 22, 2019 10:26 AM

Hello BigO

 

I still don't understand what was meant when it was said that it worked in one axis but not the other.

 

The light pen didn't work well with AtariArtist.  That's when I remembered that I had "Periphery Test" (or something with a similar name, sorry, my memory is missing a few refreshes) on a flashcart.  So we tried that.  The "Light Pen" test shows horizontal and vertical position separately.  One of the values changed when we moved the light pen, the other one didn't.  We moved it all across the screen, horizontally and vertically.  We tried two different CRT monitors (different brand) and two different computers.  Same problem.  When I tried the same software with my own light pen (CX-75, same as luckybuck's), both the horizontal AND the vertical value changed.

 

Sincerely

 

Mathy

 

PS Cash was playing a light gun game when Luckybuck remembered he had packed his light pen for testing...



#45 Mathy ONLINE  

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Posted Mon Apr 22, 2019 10:27 AM

Hello guys

 

But I still don't understand why a light pen or a light gun would work in one but not the other direction.

 

Sincerely

 

Mathy



#46 luckybuck OFFLINE  

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Posted Mon Apr 22, 2019 10:37 AM

Thanks Mathy, I am still behind two cups of coffee for full brain power and memory... Maybe, too many Easter Eggs around here...

 

Yes, that is really a mystery. But on the other hand, that is nearly on all things I touch...

 

A complete disassembly and we could measure the electronic elements. But will the stick do look the same then? ;-)



#47 BigO OFFLINE  

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Posted Mon Apr 22, 2019 10:43 AM

Hello guys

 

But I still don't understand why a light pen or a light gun would work in one but not the other direction.

 

Sincerely

 

Mathy

I'm with Mathy on this. As far as I know, a light pen doesn't know anything about direction or axis or the position of the detected pixel in any way. It sees light above a pre-established threshold of brightness and says "I see it!". It's up to the external hardware/software to know which pixel/position was being illuminated when the pen reported detection.

 

I'm just making stuff up here, but my troubleshooting thought process is wanting me to think:

  • It may have been detecting/reporting intermittently due to an electrical failure (bad cable) or failure in the active electronics.
  • Or is mechanically out of spec such that it may have been detecting only when held at a very specific angle to the screen.
  • Or maybe the brightness of the screen was just barely at the threshold of detection (possibly due to a defective sensor) so the illuminated pixel could sometimes be detected and sometimes not.

It'll be interesting to see the ultimate outcome. This is how we learn. :)



#48 luckybuck OFFLINE  

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Posted Mon Apr 22, 2019 10:58 AM

@BigO: I think it is point 1 from you.

 

Point 2: we already tested with different angles on different monitors.

 

Point 3: If brightness is the case, then why did the light gun worked as a charm? Why one axis and not the other...

 

Therefore, only point 1 matches all cases in one, to my mind. Sadly, we have to wait until the end of May for the next meeting to test... ;-)



#49 Allan OFFLINE  

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Posted Mon Apr 22, 2019 12:23 PM

Don't forget Atari made two different versions of light pens and the first one was dropped due to problems.

#50 Mclaneinc OFFLINE  

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Posted Mon Apr 22, 2019 12:42 PM

Getting it apart will be a nightmare if you are worried about the state of it afterwards...Good luck with that..







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