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Troubleshooting an APF TV Fun


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I've been looking to repair an APF TV Fun console I acquired some time ago, and now that Ive put together some decent electronics skills, I thought Id make an attempt. It's based off the ubiquitous AY-3-8500 and the data sheets are readily available.

The issue with it is that the left paddle doesn't appear on screen. Everything else seems to work ok - though everything does seem slightly dimmer than usual. And a little brighter when the right paddle and the screen boarders overlap.

I replaced the electrolytics, and the traced from pin 10, and everything seems a-ok on that front, but the problem remains.

Any ideas?

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  • 3 weeks later...
  • 3 years later...

I realize this is a few years late, but I recently had the exact same problem and found no obvious answer online.


After cleaning, testing, swapping components with working systems, all to no avail, it occurred to me that the problem wasn't with the system itself, but with the TV being used.  How could so many people (well....at least three, based on my online sleuthing :) ) have the exact same problem with their APF systems?  It turns out that on some of the APF TV Fun variants (I had this problem on *both* the 442 and 444 models, but not the 401A), the left paddle is black.  On a TV with a pure black background, the left paddle disappears.  I mean, it's there--collision with the ball works, and you can see the paddle when it crosses the edge of the playing field, but it's otherwise black on black.


My more 'modern' CRT (from the 90's) didn't show anything.  When I pulled out an older CRT (from the 70s, shown here) tuned a little differently, with a dark gray background, the paddle(s) shows up clearly.


At this point, I'm really just posting to archive this solution for future people who are digging around for an answer.  It's likely your system is fine, just tune your TV to give you an off-black background.


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  • 6 months later...

Sorry to dig this thread up, but I just wanted to add to this just in case any of the five people who own one of these don't want to deal with the left paddle being nearly if not totally invisible on modern screens.


I got my hands on an APF TV Fun model 444 recently, which has the black left paddle. I modified mine to make the left paddle white, which is actually really simple to do. Pin 10 of the AY-3-8500 is the output for the left paddle, and that signal gets fed through a transistor, then a CD4001BE (a little IC with four NOR gates), and finally passes through a 2.7k resistor before meeting up with the other output signals.


What I've done is I removed the transistor and bridged the signal through. The result at that point was a grey paddle, so then I replaced the 2.7k resistor with a 1.5k one instead to balance the colors back out. The result is a game that's actually playable on modern TVs.


I hope this helps anyone else frantically rummaging through old forum posts for a solution to this like I was!



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