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Having a couple graphics glitches with certain games


sirlynxalot

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I've attached a short video to show how Ms Pac Man runs on my 7800.

 

Full disclosure, I'm using the RF connection on a circa 2012 LCD TV, so you might think there could be some incompatibilities there with the modern TV picking up the 7800's signal, and there is the odd flicker here and there in other games... however, Ms Pac Man is the only one that is this incredibly bad. Pole Position also has a similar graphics issue but it goes away once the car starts moving.  All other 10 or so 7800 games I've tested out seem to be unaffected.  I also haven't had this issue with a multitude of 2600 games I've tested out.

 

So what do you think? Is this an issue with components in the console? my TV's issue picking up the 7800's signal? or the individual game cart being defective in some way? 

 

*Edit:  The video doesn't seem to display on the forum so here is a link to it hosted elsewhere, though the site says the video will be deleted within 24 hours since I'm not a member so it may not be available by Wednesday.

https://www.veed.io/view/f65724b3-762b-4d6f-b16f-f531cfec2914?sharingWidget=true

 

 

Edited by sirlynxalot
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11 hours ago, sirlynxalot said:

So what do you think? Is this an issue with components in the console? my TV's issue picking up the 7800's signal? or the individual game cart being defective in some way? 

To my eye, it appears as though like the TV doesn't like the signal that the 7800 is sending it.  Given that many other games work fine, I'm doubting that it's the 7800 for now.

 

One thing I'm not sure of is if Ms. Pac-Man and / or Pole Position use overscan to generate their displays.  If so, the TV may not respond well to it, which could account for the rolling / bouncing effect.

11 hours ago, sirlynxalot said:

I'm using the RF connection on a circa 2012 LCD TV, so you might think there could be some incompatibilities there with the modern TV picking up the 7800's signal

Possibly, but I'd expect an older TV to have at least a moderately-decent analogue tuner.  In general, the newer the TV the crappier the analogue tuner inside (assuming it even has one; many are now digital-only) due to the fact that analogue RF is pretty much dead as a method of connecting stuff to TVs.

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The fact that there is static in the audio, tells me that the TV doesn't seem to be quite locking onto the signal for the 7800 properly. And as far as I know, there aren't any 7800 games that abuse the scanline rules on NTSC games, but if there are, I'm sure someone will jump in to let us know.

 

 

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11 hours ago, sirlynxalot said:

So what do you think? Is this an issue with components in the console? my TV's issue picking up the 7800's signal? or the individual game cart being defective in some way? 

By chance are you trying to run an NTSC game on a PAL console? I've gotten strange video when doing that, and when it does work out it's with the best case of video glitches at the top/bottom of the screen.

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It's an NTSC system and theoretically should be an NTSC ms pacman cart.

 

It kinda reminds me of the screen rolling I'd get trying to play xonox's artillery duel on 2600, which I think had some kind of aetypical scan line issue unique to that game that certain TV's couldn't handle well. 

 

Like I said I've successfully played many other 7800 games without these issues on this same console last night before and after trying ms PAC man (and then trying ms PAC man a few more times) so kinda leaning away from the idea that my TV is incompatible with the 7800s signal and leaning more towards the game does something aetypical with it's display.  I'll also give cleaning the cart pins a shot today and see if that improves anything.

Edited by sirlynxalot
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  • 2 weeks later...

So... Lately the issues with Ms Pac Man and Pole Position seem to be non-existent!

 

Basically the only things I've done in the last two weeks are:

1) Leave the AC adapter plugged into the wall all the time, where it stays warm

2) Play the 7800 periodically

 

This 7800 and power supply was one I got off ebay in a "for parts" lot. It worked first try, so the seller must not have known how to hook it up to a modern TV.  My layman's idea is that this 7800 was therefore in longterm storage without being used for years (decades?) before I got it, and that simply by having it hooked up and playing it, that was beneficial to capacitors/the power supply.

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