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Mclaneinc

USB PSU, any good?

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Just realised I have only one working XL / XE psu, I keep seeing the USB ones but are they any good, reliable, dangerous etc etc..

 

I have about 3 things on my USB 3.0 hub but Dells are underpowered in the PSU department, would 1.5 to 2amps coming off the USB be ok...

 

Thanks for any answers..Saw a few ingots for sale on ebay, I wonder why :)

 

Needless to say I won't get one of those..

 

Thanks

 

Paul..

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I use these on ebay.   PE1170-1SA1
I had problem with video quality with a genuine pi psu.  Suspect lack of filtering in psu, its probably on the pi.

Never had any issues with these, 3 amp output.  Powering my 600xl with u1mb, dual pokey, avg cart, sdrive max.   All work perfect.    

I even use one with a pi 3 in a little arcade cab, powering pi, amp, and lcd.

 

Just need a 7 pin din, or cut one off an existing ingot.


Cisco and Liteon branded.

Cost around £7 delivered.

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I've thought about this item.   Never bought one yet, but thought this would avoid hacking up an Atari power supply for the 7 pin din connector and then having to solder it together safely and make it look nice.   It's a little expensive once you consider the shipping as well though, so that's why I haven't done it yet.   Plus I still have plenty of working Atari power supplies (not counting the ingots!).

 

Thought I'd share though...

 

https://ebay.us/Jn8oDP

 

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It's really easy if you have an old 8-bit PSU that you can cut the cable and DIN off of and use. Otherwise, you can buy a package of 5 7-pin male DIN connectors for about $5-$7, and I use CanaKit 5V 2.5A Raspberry Pi 3 B+ power supplies and have not had any issues whatsoever with them. So, by the time I buy the DINs and the CanaKit PSUs, I have about $12 in a new power supply that will have no trouble meeting the power requirements of any old XL or XE I use them on, 1200XL excluded. $10.50 if I have an old PSU to cut the DIN and cable off of. The good part is it's usable pretty much worldwide with a simple adapter plug. No converter or transformer required.

 

This link is the one I use from the U.S. Amazon site.

 

https://www.amazon.com/gp/product/B00MARDJZ4/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

 

I looked at the U.K. Amazon site and saw some CanaKit PSUs as part of kits, but I didn't see them available à la carte.

 

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6 minutes ago, erichenneke said:

I've thought about this item.   Never bought one yet, but thought this would avoid hacking up an Atari power supply for the 7 pin din connector and then having to solder it together safely and make it look nice.   It's a little expensive once you consider the shipping as well though, so that's why I haven't done it yet.   Plus I still have plenty of working Atari power supplies (not counting the ingots!).

 

Thought I'd share though...

 

https://ebay.us/Jn8oDP

 

That would be a good one. Marlin at The Brewing Academy makes great stuff and he stands behind everything he makes. That's just the cable, and you'd need to provide your own charger/power block. He sells one that is the whole PSU as well, from his site. He sells it on ebay as well. It looks like it might be just a tad bit cheaper to order from his site rather than through ebay, but your mileage may vary.

 

https://thebrewingacademy.com/collections/atari-800-xl-xe-xel-xld/products/atari-xl-xe-replacement-power-supply

 

https://www.ebay.com/itm/Atari-XL-XE-Replacement-Power-Supply-2amps-US-OR-UK/283869848834?hash=item4217f62502:g:5ycAAOSwEX5b22yn

 

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I'm just about sure I read here that some USB PSUs generate lots of noise.

I guess it's totally feasible that some cheap ones with poor filtering could let AC noise through.

 

The plug - only two wires are actually used so even if your soldering aint that great it's not an entirely hard job to make one up.

I've been meaning to make one for some time.

 

In fact, I've bought some of the cheap micro USB breakout boards on fleaBay - the plan there is to make an adaptor so I can just use a USB charger + normal USB cable same as charging a phone.

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Hello guys

 

I bought some switching power supply wall thingies years ago.  HARdwareDoc recommended them.  They came with a round plug, I guess like those we know from the XEP80 and the 2600.  I made a small adaptor cable for all of those.  That way you don't void the warranty on the power supplies and if you do have to replace them, you just unplug one power supply and plug in another.

 

Sincerely

 

Mathy

 

 

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8 minutes ago, Rybags said:

I'm just about sure I read here that some USB PSUs generate lots of noise.

I guess it's totally feasible that some cheap ones with poor filtering could let AC noise through.

 

 

The ones I use from CanaKit come with an in-line noise filter. I'm sure many cheap one's don't though.

 

9 minutes ago, Rybags said:

The plug - only two wires are actually used so even if your soldering aint that great it's not an entirely hard job to make one up.

 

 

 

You bring up a good point here. Three of the seven connections inside the DIN were all common and wired to +5VDC, while three of the others were also common, and wired to ground. Then those common points come into the motherboard and are again brought together. Does anyone have any idea why they did this? It seems kind of overkill for +5VDC and less than 2amps.

 

When I make mine up, I wire to one of each on each side of the connector, then short the other two to it, just like the originals were done, but I really don't know what purpose it serves.

 

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I'd say they chose a 7 over 2 pin off-the-shelf connector to lessen the chance of people using incorrect PSUs.

Of course that was a huge failure since the C64 one will work and kill the machine in the process.

 

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What I would love to see is an adapter for 7-pin Atari power input to a female USB-B micro or USB-C connector.  There are a bunch of 2A-plus RasPi power supplies laying around here doing nothing, which would make great candidates for powering various bits of Atari XL/XE hardware.  Purchasing another power supply seems redundant when there are ones here that could be reused.

 

@MacRorie: is this something that might worth adding to TBA's repower options?

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6 hours ago, bfollowell said:

Three of the seven connections inside the DIN were all common and wired to +5VDC, while three of the others were also common, and wired to ground. Then those common points come into the motherboard and are again brought together. Does anyone have any idea why they did this? It seems kind of overkill for +5VDC and less than 2amps.

I know from making a few USB-power cables, that many USB cables use really small guage wires as small as 28AWG, which pretty high resistance/impedance, so that even if the power supply is outputting a good 5VDC, what you get out of the other end of 6ft of small guage wire is 4.7V or lower. To combat voltage drop in the XL/XE's, stock Atari power supplies use really fat 18AWG wire, and the intent of the three pins each for +5V/GND must have only been to improve the conductivity when entering the machine as well.

 

There is a market for USB cables with up to 20AWG wires, to improve mobile phone charging speeds at higher amperages as well... Here's one of a few cables I made using a cable from an old dead USB mouse (28AWG), connected to the lead cut from an Ingot (18AWG)... this particular cable has a decent voltage drop -- it's possible it could be improved by cutting the length of the 28AWG mouse cable down to just a couple of inches after the old ingot cable instead of 2-3 feet.

 

But basically you can re-purpose any power supply that outputs 5V DC of at least 1A - 2A is less likely to exhibit high frequency noise into your video picture, not from AC but from the switch-mode power supply that toggles power output at something like 10,000hz - if the output filter capacitors are insufficient, it shows up as a strange subtle but noticeable noise pattern in the output video. 2A+ supplies are less likely to exhibit it under load, but you never know.. If you have a drawer full of old PSU's I'd start by just hacking ends onto those before buying fancy new ones. :) Then measure the 5V DC from the joystick or SIO port and see how far off you get from 5.0V.. 4.8-5.2V might be just fine. 4.6V and lower starts screwing up the colour...

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7 hours ago, bfollowell said:

 

You bring up a good point here. Three of the seven connections inside the DIN were all common and wired to +5VDC, while three of the others were also common, and wired to ground. Then those common points come into the motherboard and are again brought together. Does anyone have any idea why they did this? It seems kind of overkill for +5VDC and less than 2amps.

 

When I make mine up, I wire to one of each on each side of the connector, then short the other two to it, just like the originals were done, but I really don't know what purpose it serves.

 

It is to reduce the total resistance. Assuming resistance of 1 pin is Rpin, then using three pins in parallel gives the following resistance:

Req=(3/Rpin)^-1. If the resistance of one pin is 1 Ohm, then three pins give 0,333 Ohms.

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Yeah, I'm using a Pi power supply for my two 800XLs and they're both working fine. No noise in the video or audio (though I have also replace the capacitors on the boards which might be helping there).

 

As for the 3 pins instead of 1, indeed it's about reducing the contact resistance. To add to the answer above, even if the resistance allows 2A to flow, it introduces a voltage drop. While 1 ohm is a *very* bad contact, it's not out of the realms of possibility on ~40 year old connectors. But let's take 0.2 ohms as an example. If you have 0.2 ohms for each contact, that means that, at 1.5A consumption, you will get a 0.3V drop across that contact. If it's the same on the negative size as well, then that's a 0.6V drop, so the machine only gets 4.4V of the 5V the PSU is producing. That's low enough to cause random crashing, colour issues, even failure to start, despite the machine getting 1.5A of current. If all three contacts are used on both the positive and negative sides, the voltage drop is reduced to 0.2V, leaving the machine with 4.8V to work with. While slightly low, it's close enough to 5V that there shouldn't be any issues and the machine should work perfectly fine.

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23 hours ago, Rybags said:

I'm just about sure I read here that some USB PSUs generate lots of noise.

I guess it's totally feasible that some cheap ones with poor filtering could let AC noise through.

They tend to, some worse than others and some so bad that the screen almost rolls. Their job is to charge so why would they waste $$ for more filtering. I have a PSP-100 charger as a backup, and there is notable difference on the screen between that and my Atari power supply in terms of quality, once you see it.. it's really hard to unsee.

 

Use a proper power supply. Those cheap ass ones can cause house fires.

 

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On 11/18/2020 at 7:27 AM, Mclaneinc said:

 

I have about 3 things on my USB 3.0 hub but Dells are underpowered in the PSU department, would 1.5 to 2amps coming off the USB be ok...

 

That's actually quite interesting, I've never thought to try my Targus powered USB hub or just the switching adaptor it runs off ( 5v 4.0a output )

 

https://au.targus.com/products/usb-3-0-7-port-powered-hub-ach125au

Edited by shoestring

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On 11/17/2020 at 5:18 PM, x=usr(1536) said:

What I would love to see is an adapter for 7-pin Atari power input to a female USB-B micro or USB-C connector.  There are a bunch of 2A-plus RasPi power supplies laying around here doing nothing, which would make great candidates for powering various bits of Atari XL/XE hardware.  Purchasing another power supply seems redundant when there are ones here that could be reused.

 

@MacRorie: is this something that might worth adding to TBA's repower options?

I mean, sure.  Give me pictures of what you want and I will go about making it. 

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10 minutes ago, MacRorie said:

I mean, sure.  Give me pictures of what you want and I will go about making it. 

I think that's genius. A USB-DIN Plug adapter. Hummmm.

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35 minutes ago, MacRorie said:

I mean, sure.  Give me pictures of what you want and I will go about making it. 

What about selling a version of that same cable (usb to din) with this additional little gadget (or similar)? It might be popular.

https://www.ebay.com/itm/USB-Volt-Current-Voltage-Doctor-Charger-Capacity-Power-Bank-Tester-Meter-PZ/203042774423

 

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52 minutes ago, MacRorie said:

I mean, sure.  Give me pictures of what you want and I will go about making it. 

 

If I draw out what I'm thinking of, it's going to end up resembling nothing at all like what's in my mind.

 

But I can steal a photo from TBA's website and annotate the daylights out of it in Preview :D

 

image.thumb.png.843a5e726b464dffa5770406f0bb9f72.png

 

The option of different cable lengths might not be a bad one, if it wouldn't be too much of a PITA to produce.

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