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Atari 800 power adapter: Can I use DC? 5200 adapter?


CZroe
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A couple days ago I picked up an Atari 800 with only the BASIC cartridge (no cable, manuals etc.). I looked up the specs and realized that it takes an AC-to-AC adapter, much like the Nintendo Entertainment System. Also like the NES, I assume it will also work with an AC-DC adapter.

 

I also read some specs from an old newsgroup FAQ and saw that the Atari 800 originally had a 9v 18.5w adapter but that it was barely adequate and Atari respec'ed it to require 19w. I also saw that they used a 50w adapter that supported just about all the Atari 8-bit line.

 

With all this in mind: I have a "Vanco" replacement adapter for my 4-port Atari 5200 and I'm curious to know if it can pull double-duty. It's 11.5v 1.95A (22.5w) AC-DC but I assume that the Atari 800's voltage regulator can handle it and that the AC rectifier will just pass through the DC current?

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Just buy a new old stock power supply from best electronics. Done. No worries, no fried computer.

Yeah, that's still an option, but I'm trying my best to keep this under the normal going rate for an Atari 800 that includes it all in the first place. I already paid $40 for the Atari 800 without even testing it and I don't want to dump too much more money into it.

 

Similarly, a friend and I each obtained an Atari 7800 at the same flea market two weeks ago. His was untested with no power adapter and mine was supposedly tested with everything. We quickly discovered that mine didn't power on and his did. At least I knew my power adapter was good, so I told him that he could have it after I was done checking out my 7800. Sure enough, it was just a bad power button. Because I'm having to modify mine anyway, it makes sense to go all the way with the S-Video mod and a standard power jack so that we can each have functional consoles. Charitable, cheap, and efficient. :) I'd like to find an cheap alternative here as well.

 

Pics: https://imgur.com/a/pVRvr

 

The NES AC Adapter is only 1.3A (11.7w) making it inadequate. The replacement from Best Electronics says 18.5w, which Atari themselves deemed to be inadequate. If I can overcompensate with something like the 31w(50w Max) C017945/CA017964 (Atari's most versatile 8-bit adapter) does without having to pay over $10, I'll be a happy camper, but I thought it might be worth checking to see if the Vanco can be used for both (seems like it could).

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My 2 cents.

 

I'd suggest you have a look at the info here: http://www.atarimania.com/faq-atari-400-800-xl-xe-what-are-the-power-requirements-for-my-atari-components_44.html

 

It goes into the specs for power supplies for lots of Atari's, 800 included.

 

A swift look confirms that the 800 requires an AC/AC power supply, so I would recommend you don't try and pump DC through the rectifier, as you may well get a voltage drop across it that means you don't have the required power to run the 800, plus given the recifier's age, it may not handle it well.

 

IMHO, you'd be better off hanging back until you can afford a replacement form Best, or try somewhere like Element14 for an equivalent. I got a PSU for £6.52 from Element 14 in the UK that is AC/AC for a 1010 which meets the specs on the link above, I'm sure that they will have something that will work for an 800.

 

Less risk of fried 800!!

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My 2 cents.

 

I'd suggest you have a look at the info here: http://www.atarimania.com/faq-atari-400-800-xl-xe-what-are-the-power-requirements-for-my-atari-components_44.html

 

It goes into the specs for power supplies for lots of Atari's, 800 included.

 

A swift look confirms that the 800 requires an AC/AC power supply, so I would recommend you don't try and pump DC through the rectifier, as you may well get a voltage drop across it that means you don't have the required power to run the 800, plus given the recifier's age, it may not handle it well.

 

IMHO, you'd be better off hanging back until you can afford a replacement form Best, or try somewhere like Element14 for an equivalent. I got a PSU for £6.52 from Element 14 in the UK that is AC/AC for a 1010 which meets the specs on the link above, I'm sure that they will have something that will work for an 800.

 

Less risk of fried 800!!

Thanks. That's the same newsgroup info I've been reading. Anyway, the Vanco 5200 adapter already outputs a higher voltage with enough amps that I wouldn't be concerned about voltage drop and would be more concerned with heat from the voltage regulator.

 

As for all this concern about the rectifier: I don't understand. No one thinks twice about using a DC Sega Mega Drive/Genesis adapter on an NES designed to accept AC and pretty much every aftermarket NES plug is DC (often sold as a "universal" Genesis/NES/Jaguar plug). Relatively, the NES is almost as old too. Is there something that makes the Atari 800's rectifier more sensitive? The bit about internally generating -12v might be relevant. I probably sound like I know more about power supply design than I do: Would an engineer ever have to generate positive voltage from one phase of AC and negative from the other?

Edited by CZroe
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The OEM 16K memory cards for the 400/800 contain 4116 RAM chips which require three different DC voltages(+5V/+12V/-5V). The stock power supply board isn't able to generate all 3 from a DC power supply no matter what the voltage or amperage ratings. Without AC the diodes of the rectifier bridge and voltage doubler circuit would decrease the voltage available to the 7812 by 2 to 3V, and also has no ability to create -5VDC from a +DC input. The power LED also won't operate with a +VDC power supply as it is connected to -5VDC.

 

The other devices you mention have no issue because they would be using other RAM, not having the same power requirements. A 1200XL uses the same power supply as the 400/800 but could use the 5200 power supply since it's circuitry only has a single voltage requirement, +5VDC.

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As BillC stated, and I mentioned, you will get a voltage drop across diodes in the rectifier, and since you are only using 2 out of the 4 diodes within the rectifier, and it is expecting AC, you may get some big peaks and troughs in the output.

 

Since this is also a 36 year old computer, it is very likely to have tolerances that are much wider, and probably also lacks any capacitors for smoothing a DC input (I may be wrong here, I'm a bit of a lay engineer), and Atari were not notable for good circuit design, or for using the best components.

 

I guess all I'm saying is that I don't want you to damage a potentially good 800, and I know I would not pump DC into an AC device. I didn't with a relatively uncomplicated 1010 tape drive, with the much more complex 800 I simply wouldn't for fear of damaging it.

 

I know it's a bind, since I have limited funds myself, but surely getting a proper PSU would be better than having to replace the 800?

 

Just my thoughts, honestly I understand the conundrum, I've been there myself as I have a number of old Ataris, and PSU replacement is a bind.

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Well, that's exactly why I asked. Thanks guys! Great info that's much more in-depth than what I found googling. :) I wish I had a high-wattage bench power supply with options like 9v AC (you won't get that from a cheap PC PSU w/bench PSU break-out). It would sure come in useful for testing things before flushing too much more money on an untested system that may not work.

 

Before I resort to ordering one I'm going to go back to the pawn shop and dig around in their cords some more to see if it got separated. I didn't look too hard before because the specs weren't printed on the chassis anywhere and I assumed I could get a generic power adapter online easily/cheaply enough. I knew the Atari 5200 was basically a cut-down 400/800 and also kinda hoped they used the exact same adapter. After finding out that they did not, I hung on to that hopeful idea a bit longer due to my experience with the NES. Now I know better. Thanks again! :)

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  • 1 month later...

Forgot to update this thread. Got this a month ago:

2e3c4bafac48d3d92d02d334d7001fa5.jpg

Had to buy a bit more of the seller's gaming stuff than I otherwise would have but ultimately I got it for about $10. The 800 worked but the BASIC cart and the Start key did not. I may have fixed the start key by flooding it with 99.9% Isopropyl and working it a lot but Atari BASIC appears dead as a doornail. After a few weeks the Start key still works but it sometimes misses a press. I'll try reflowing the cart's components soon (mine's not socketed).

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  • 1 year later...
  • 4 months later...

Isn't that the CO18187 A/C adaptor the 5200 uses or the 1050 one? Aren't those DC?

It was the right adapter... C014319, I think. It does look surprisingly like a 5200 adapter, but it’s definitely not.

 

On a related note, a couple months ago my brother came home with the notorious “ingot” PSU for 800XL. It also looks very similar. I was blessed with the better PSU for my 800XL but I’m still tempted to crack it open and restore the ingot with a modern, reliable, PSU... similar to the C64 “rebrick.”

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On a related note, a couple months ago my brother came home with the notorious “ingot” PSU for 800XL. It also looks very similar. I was blessed with the better PSU for my 800XL but I’m still tempted to crack it open and restore the ingot with a modern, reliable, PSU... similar to the C64 “rebrick.”

 

Cut off the cords. Toss the brick. Every ingot on earth needs this done.

 

Solder the nice Din5 cord to a modern regulated 2.0A or higher 5V DC PSU.

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Cut off the cords. Toss the brick. Every ingot on earth needs this done.

 

Solder the nice Din5 cord to a modern regulated 2.0A or higher 5V DC PSU.

 

Exactly! Hell, even a $10 CanaKit Raspberry Pi adapter is 2.5A these days. NO reason whatsoever to ever use an Ingot with an XL or XE machine.

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Pulled it out of the freezer, whacked it a few times, pried it apart, and now we have this:

c7704fe3fe634dddf031232dcbb1da16.jpg

The old resin brick with encapsulated PSU has been removed. The wires have been cut on the inside with enough length to attach to something else. All I have to do now is throw an appropriate modern PSU inside and button it back up. B)

 

Literally the only difference from what was suggested is that I preserved the original plastic box and strain reliefs. :)

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LOL....need more pics of this !!! I'd love to see what kind of AC-DC conversion and voltage regulation is inside an Ingot :D

Why not try measure the VAC output of the Ingot's transformer. Much like the the C64 supply, it's not the transformer that is bad but the AC to DC conversion and even more the voltage regulation bit.

 

If the Ingot pumps out about 11-12 VAC without a load, simply ad a fuse on the secundary side and you're good to hook it up to a 800.

 

Putting a modern day switching voltage regulator (like the C64 PSU hacks) in there which converts AC to DC and then having he 800 having to deal with the DC voltage seems to be an unnecessary step.

 

 

[EDIT] Forget this.....I don't think you'll be able to separate the transformers output from the AC/DC/regulation section.

Edited by Level42
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LOL....need more pics of this !!! I'd love to see what kind of AC-DC conversion and voltage regulation is inside an Ingot :D

 

Why not try measure the VAC output of the Ingot's transformer. Much like the the C64 supply, it's not the transformer that is bad but the AC to DC conversion and even more the voltage regulation bit.

 

If the Ingot pumps out about 11-12 VAC without a load, simply ad a fuse on the secundary side and you're good to hook it up to a 800.

 

Putting a modern day switching voltage regulator (like the C64 PSU hacks) in there which converts AC to DC and then having he 800 having to deal with the DC voltage seems to be an unnecessary step.

 

 

[EDIT] Forget this.....I don't think you'll be able to separate the transformers output from the AC/DC/regulation section.

LOL! Yeah, I didn’t even bother testing t before breaking open and the board was broken in half in the process...

a0da49a97adc45dcff4662c747ab4f59.jpg

b3f66c9e8ffeaf988f7a005d68fc9f75.jpg

 

It was quite a bit more difficult than a C64 PSU because it has posts on the top and bottom that the resin solidified around. That makes it held in the top a lot stronger. I definitely downplayed the difficulty since it took some prying and drilling too. Wouldn’t recommend it!

 

chisel or sledge hammer YOU DECIDE lol

 

I vote sledge hammer!

Why not both? ;) I hammered the pointy end of the file down into it and used it to whack the metal spudgers along every wall then pried and banged and drilled until a crack formed in the resin and the rest finally fell out.
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I still wonder why they actually did (do?) put transformers and all electronics into resin. Mind you....it does make a great paper-weight....

Yeah. Just seems weird that they would add the weight and expense for no reason. Perhaps it also works as a heat sink and ensures that nothing will ever bend/contact. There is a big, winding, metal heatsink embedded in the resin (not talking about the plates on the transformer).
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