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BigO

Member Since 5 Feb 2007
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In Topic: How to repair a CX-75 LightPen?

Fri Apr 19, 2019 10:27 AM

Thanks BigO,

'Is not the sensor itself is a single element, one-dimensional device?' I assume so, that is why I asked for a take away part guide.

'What was the failure mode?' We tested many different light pen programs, including Atari Graphics cart and that SALT 2.07 cart. All have that problem.

'Did it appear to detect the exact same position all the time on the broken axis?' Yes!!! Totally forgot, thank you so much, it was frozen in the lower left corner! Good point!

Have made a photo of the light pen head, please see below.

Hmm...frozen in the lower left corner does not equate in my mind to working in one axis.

 

That sounds like working in no axes, possibly not detecting the light at all. Which would lend credence to the theory about the brightness of the screen. Or maybe the sensor became less sensitive due to optics or electronics. Maybe the sensor failed entirely.

 

If you knew more about the electronics, you could probably build a static test harness fairly easily. Knowing the pinout of the device would probably be enough to give that a try. 


In Topic: How to repair a CX-75 LightPen?

Fri Apr 19, 2019 10:11 AM

@BigO: $24.2 plus customs plus tax for overseas... will result in something like > $30... But the price is not the problem, but they why, especially for others. For the computers we have:

Technical Reference Notes or Manuals, else Hardware Manual. But not for the light pen. :-( Would love to add this for the Wiki.

Understood. If I had a use for a lightpen, I'd probably pick up that eBay one since I'm in the US. But, I wouldn't pay $30 either.

 

I was searching around a little and found almost no useful information on the CX-75, so I respect what you're doing in terms of discovering and documenting. Too bad you can't pick up a working version for reference, though.

 

I assume someone can or has disassembled/decompiled software to see exactly how it's reading from the pen in case there are any clues there.

 

Good luck with your efforts.


In Topic: How to repair a CX-75 LightPen?

Fri Apr 19, 2019 9:10 AM

You might also "fix" it by buying one for $7.95 on eBay. :)
https://www.ebay.com...tsAAOSwa1ZcBgjD


In Topic: How to repair a CX-75 LightPen?

Fri Apr 19, 2019 9:04 AM

I'm curiously following this just because it runs contrary to the little knowledge I have of light pens and I expect that I'll learn more from the ultimate fix of this problem.

 

As I understand it, the sensor in a light pen detects light of a given brightness or it does not. Only the driving host device knows how to interpret the position based on the timing of the light detection. Only the pixel being currently drawn should be bright enough to trigger the sensor. The light gun itself shouldn't have any clue where the pixel is that it just detected.

 

So, I'm really curious how the light pen itself could be responsible for making one axis function but not the other. Is not the sensor itself is a single element, one-dimensional device? 

 

What was the failure mode? Did it appear to detect the exact same position all the time on the broken axis? Or did it appear to detect light at every position on the broken axis? Or did it appear to just be off by a few rows/columns in the broken axis? Would the mismatch in position change if you rotate the barrel of the light pen as though the input optics were not reading directly out in front of the sensor?

 

Maybe the polling logic actually somehow/somewhy (<< should be a word) reads the sensor twice to determine X and Y position and a pulse for one of those reads is too short to activate a weak, failing component? I'm really just making stuff up here but am interested in seeing what the real reason turns out to be.


In Topic: Kid Vid Tape Recorder Options\Help Needed

Sat Apr 13, 2019 5:28 PM

If the tape you mentioned earlier is in your possession, you might try ripping it to an MP3/WAV/whatever and posting it up. Somebody might run with it.

Maybe somebody can identify the serial communication protocol. That might be enough to get somebody interested in pursuing an adapter or a solid state Kid Vid emulator.

 

The hardware side should be doable if somebody wanted to build a solid state Kid Vid emulator. There are cheap MP3 modules and Arduinos out there. With those in hand, it's just a simple matter of programming. ;)