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Best Electronics Composite Mod for 7800


Tonyscouter

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I purchased an NTSC 7800 recently and added a Best Electronics composite mod.  When I plugged it in I was not happy with the picture quality.  It had jail bars and a blurry output.  I adjusted the red coil and that minimized the jail bars but the picture still has a grid pattern to it.  Would old capacitors have something to do with it?  Any suggestions would be appreciated.

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It may not be caps, but it's hard to really take a shot at figuring out what might be going on without pictures.

 

Are you able to post a few photos of both the installed video mod and the effect you're seeing on the screen?  It'll help greatly with figuring it out.

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Definitely double-check the installation on both the composite mod and 7800 sides for any cold joints, solder bridges, components out of spec, etc.

 

Have to be honest here: my experience with the Best composite mod is nonexistent, and this is a failure mode I haven't seen before.

 

Can you post the installation instructions for this thing?  I have some idea of how it most likely attaches, but would like confirmation of how it really goes together and what's actually on the mod board.

 

It can probably be figured out, but, as recommended, go back and double-check.  I've caught obvious problems before on the 35th inspection simply because inspections 1 through 34 weren't where I saw it.

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On 4/20/2024 at 4:55 PM, Mitch said:

 it is most likely the composite mod.

 

Mitch

 

I believe Brad is still just using the most basic transistor video amp. Not gonna get a very pretty picture out of it VS all the other options available. It's a composite signal sure, but not a good one. 

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42 minutes ago, Shawn said:

I believe Brad is still just using the most basic transistor video amp.

This is my suspicion as well.  Just want to get photo confirmation and some idea of how the installation has been implemented in this case.

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9 hours ago, Tonyscouter said:

All, attached is the complete instructions for this composite mod.  I'll have time this weekend to inspect for cold joints, solder bridges etc.

 

Thanks for that; it's a lot easier to get an idea of what's going on with it.  My suggestions follow:

  • 2N3904 Transistor: check orientation (i.e., the flat side is facing the correct direction)
  • R3, R6, R11, R14: check for solder bridges, things contacting other things that they shouldn't be, that the correct resistors were removed, etc.
  • L3: Same as for the resistors.  Pay particular attention around the crystal (Y1).
  • If still installed, make sure that nothing can contact the RF shield.

Now for the part that has me biting my tongue for a number of reasons:

 

image.thumb.png.989ca1144d56e55f9637f13f94c1f203.png

That's just...  Wow.  Not having seen this mod before, it's something of a surprise to see what the kit actually consists of, how much modification of the console is necessary to make it work, and the end result of the installed product.  There are about a dozen things in the general area of that transistor which could go wrong, and it doesn't seem like there's a single point of failure than can be definitively pointed at.  Hate to sound like a broken record, but go back and check everything for solder bridges, miswiring, shorts, etc.

 

At the end of the day, it'll work - but that's a pretty prehistoric way of doing it.  I'm not criticising you for going with this mod, but you may want to consider returning the machine to stock and installing a UAV.  Should you end up doing this, the version with @-^CrossBow^-'s mount board is strongly recommended.

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3 hours ago, x=usr(1536) said:

That's just...  Wow.  Not having seen this mod before, it's something of a surprise to see what the kit actually consists of, how much modification of the console is necessary to make it work, and the end result of the installed product.  There are about a dozen things in the general area of that transistor which could go wrong, and it doesn't seem like there's a single point of failure than can be definitively pointed at.  Hate to sound like a broken record, but go back and check everything for solder bridges, miswiring, shorts, etc.

 

At the end of the day, it'll work - but that's a pretty prehistoric way of doing it.  I'm not criticising you for going with this mod, but you may want to consider returning the machine to stock and installing a UAV.  Should you end up doing this, the version with @-^CrossBow^-'s mount board is strongly recommended.

Some perspective here.  The mod became available from Best Electronics ~15 years ago: https://web.archive.org/web/20101119105730/http://best-electronics-ca.com/7800.htm

 

Arguably, it was the first Composite mod of its time for the 7800, as it is based from the work that Atari Engineers performed ~20 years prior to that.  So, it's a ~35 year old composite mod design. 

 

Best Electronics tends to keep things as close to back in the day availability/'realness' as possible.  The site was one of the extremely few 7800 product offerings for a considerable number of years.

 

That being stated, @-^CrossBow^- is meticulous and second to none in modification and repair services.  He is highly recommended.

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1 hour ago, Trebor said:

Some perspective here.  The mod became available from Best Electronics ~15 years ago: https://web.archive.org/web/20101119105730/http://best-electronics-ca.com/7800.htm

 

Arguably, it was the first Composite mod of its time for the 7800, as it is based from the work that Atari Engineers performed ~20 years prior to that.  So, it's a ~35 year old composite mod design. 

 

Best Electronics tends to keep things as close to back in the day availability/'realness' as possible.  The site was one of the extremely few 7800 product offerings for a considerable number of years.

 

That being stated, @-^CrossBow^- is meticulous and second to none in modification and repair services.  He is highly recommended.

 

Agreed.  I should probably clarify that my intention in referring to the mod as 'prehistoric' wasn't a dig at Best (or Brad), but rather a description of the mod itself.  It could have come from anywhere and would have still received the same description.

 

Nothing wrong with the mod itself (though I do still believe it to be more involved than necessary compared to newer offerings); if it's what someone wants to use, that's their prerogrative.

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3 hours ago, mimo said:

that mod was great 20 years ago, many better options now. RGB from a GameDrive being the top of the list, then a @juansolo @marauder666 mod, then UAV (All my opinion! )

RGB from the GameDrive is currently the only option to ensure all accurate colors on a modern display. 

 

For PAL consoles, it is an item not so prevalent, but NTSC consoles, the games: Commando, Pole Position II, Basketbrawl, Dig Dug, Choplifter, and more, all demonstrate some to widespread inaccurate colors on modern displays without the RGB output in place.

 

Sticking with just the console hardware and modification for it, agreed on best output order. 

 

The most feasible option for those in NTSC regions is the UAV (tweaked) mod which when/if available, @-^CrossBow^- is my recommended go to for it.

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1 hour ago, marauder666 said:

We never did mod yours with a chroma shift circuit.  We can still do it, if you want.

 

That's very kind of you, I might take you up on that offer.

I've got a PAL 7800 that won't display an image, if you are up for looking at that I could get them posted ? 

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On 4/27/2024 at 3:22 PM, Paul Westphal said:

I have used the Best mod and there are others out there that are much better. I think his mod is as old as his website 😂

Yeah, I had a friend fix the mod he did for me about a decade ago. It wasn't bad, but it's not great electrical work.

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  • 2 weeks later...

Thanks for everyone's input.  I might have had a cold solder joint that caused the bad picture.  What I ended up doing was removing the components from Best Electronics kit and installed a Vintage Gaming and More circuit board.  It required less modification to the motherboard and no components are left suspended in the air.  The picture quality is now fine.  I did keep the cable that came with the kit so I didn't have to drill into the side of the unit. 

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