2600 power jack to USB

[konnann]

I saw someone was replacing the 2600 power jack with a mini usb plug. 

Just curious if anyone knows how they might be doing this? Maybe using a breakout board or a converter?

[+Stephen Moss]

It depends on what they are doing, I presume they are just intending to use a 5V DC USB power source like a phone/tablet/Sat Nav charger to power the 2600.  In which case the power source should output a regulated 5V supply therefore provided it can supply the required current all you need to do is connect the GND and 5V pins of the USB connector into the 2600 as you do not need the two data pins.

That said some chargers (generally those specified for multiple devices, i.e. tablet & phone) are intelligent and may power down if they do not receive a power specification from the connected device, but most, particularity the cheaper ones will not be intelligent and so should work.  

 

Where you connect the power pins of the USB connector is optional...

1) You could connect them to the same points as the existing connector (or to the 2200uF capacitor), power should still flow through the internal 5V regulator but it will not regulate, just pass the already regulated 5V supply from the power unit straight through.

2) As for option 1 but you remove the internal voltage regulator and link the points where its input and output pins were, however removing the regulator leaves the system more open to being damaged, particularly if someone not realising it now uses a 5V supply made an adaptor and powered it with a traditional 9V.

3) As the power USB unit should output a regulated +5V DC you could remove the the internal regulator and wire the USB power pins to where its GND and Output pins were, however that not only opens the system to the same potential damage mentioned in option 2 but also bypasses the power switch so you would need to use the wall switch to turn the system on/off. If you know what you are doing you could wire in system power switch as well but that requires more modification.

 

Personally, I think Option 1 is the best. Not only is it the easiest to implement, it maintains use of the systems power switch and allow the system to easily be converted back should anyone want to return it to original condition.    

[konnann]

@Stephen Moss That’s way more of an answer than I was hoping for, you the man!

I was thinking of option 1. But what are the drawbacks if any to doing this? Seems like it should have been something everyone does. 

[Rom Collector]

If it ain't broke, don't fix it.

[ChildOfCv]

The 2600 needs at least 8V input for proper function of the color delay circuit.  So you'd need to add a buck converter just after the USB plug.

[root42]

While interesting as an exercise I do not quite see the advantage of using a USB connector. There are excellent compact switching 9V power supplies available. And while the Atari's choice of connector is weird, it’s still easy to come by. 

 

Regarding buck converter: my EE is a bit rusty, but aren’t buck converters for downstepping voltage? Wouldn’t you need a boost converter to go from 5V back to 9V? And at that point it’s probably way more efficient to simply use a true 9V switching power supply. 

[konnann]

14 hours ago, Rom Collector said:

If it ain't broke, don't fix it.

Maybe it’s broke ??

[+Stephen Moss]

10 hours ago, root42 said:

While interesting as an exercise I do not quite see the advantage of using a USB connector. There are excellent compact switching 9V power supplies available. And while the Atari's choice of connector is weird, it’s still easy to come by. 

 

Regarding buck converter: my EE is a bit rusty, but aren’t buck converters for downstepping voltage? Wouldn’t you need a boost converter to go from 5V back to 9V?

A 3.5mm mono jack is not a common connection for power units these days, DC connectors (like The Jaguar power unit) and USB are more widely available and even DC connectors may be phased out with everything going USB so they are probably just future proofing making it easier to find supplies. Most people these days have several USB chargers kicking around as you get one with every new mobile phone or Sat Nav you buy so why not use what you have to hand rather than buy something.

 

Yes, Buck is for down conversion & Boost is for up conversion but they can radiate a lot of high frequency noise which may cause interference to sound/video.       

 

13 hours ago, ChildOfCv said:

The 2600 needs at least 8V input for proper function of the color delay circuit.  So you'd need to add a buck converter just after the USB plug.

You may know more about this than me so could you give a little more detail as...

From the CX2600 schematic available here the voltage references shown for the colour delay circuit appears to be GND and the two diodes which go to 5V, so where does it get the 8V from as the whole system appears to be running from the 5V regulator output?

 

From the CX2600A schematic available here the voltage source for the colour delay does appear to be direct from the incoming 9V supply, however I would think the purpose of the two diodes above the regulator and the 4K7 resistor would be to reduce the voltage to the colour delay preset to about 6.4V (5V + 2 diode Vf). If designed with any sense the correct setting should be near the middle of the preset for maximum adjustment although a 6.4V supply suggests the required voltage may be a lot closer to 5V.

Consequently, if the TIA's Del pin requires a voltage input of 5V or less  (measure using a normal 9V power source prior to making the modification) there should be enough adjustment on the preset to set the correct voltage (vary slightly from unit to unit) when using the 5V USB supply and thus maintain correct operation.

 

Or am I missing something?

[ChildOfCv]

2 hours ago, Stephen Moss said:

You may know more about this than me so could you give a little more detail as...

From the CX2600 schematic available here the voltage references shown for the colour delay circuit appears to be GND and the two diodes which go to 5V, so where does it get the 8V from as the whole system appears to be running from the 5V regulator output?

The two diodes and a capacitor are used as a Cockroft-Walton style multiplier.  Notice that it feeds in from the oscillator.  In this case, a 7V power supply with sufficient amperage would work (the data sheet says you need at least that much to provide sufficient voltage for the regulator), or you could toss the regulator entirely and supply 5V directly into the system.  So I guess with this revision you could get away with it.

 

2 hours ago, Stephen Moss said:

From the CX2600A schematic available here the voltage source for the colour delay does appear to be direct from the incoming 9V supply, however I would think the purpose of the two diodes above the regulator and the 4K7 resistor would be to reduce the voltage to the colour delay preset to about 6.4V (5V + 2 diode Vf).

Yeah that would be expected, but the Atari service manual talks about higher voltages.  Maybe they use a diode with a higher forward voltage, or maybe they're just covering their bases.  For those that use the multiplier above, they definitely expect to see a higher voltage on the delay resistor.  But either way, you definitely need more than 5V on this revision to get the spec'd voltage range on the delay.

 

Of course, the most obvious way to get an acceptable voltage with this revision would be to convert it to the CX2600 design.

Edited August 14, 2019 by ChildOfCv

[Rom Collector]

21 hours ago, konnann said:

Maybe it’s broke ??

I should have just said it's a stupid idea.

[+-^CrossBow^-]

Well, I can tell you that with at least 3 different 4 switch units in the past, I would use a universal multivoltage supply with them. One of those that goes from like 5v - 12v etc. With that PSU if I dropped it down to 6v, the Atari would power on and basically work, but the colors were all screwed up and would shift hues in the middle of the graphics. I want to say the lowest setting I could get to work was 7.5v on that PSU. I might still have it kicking around and can try it again, but that would seem to be evidence to what @ChildOfCv was stating in regards to the color circuit needing more than 5v to work properly.

 

[Mark loves Stella]

I installed a USB power jack on my Atari 7800 using a step up converter. Works great. Your USB 5v power source will need at least 2 amps. At least for the 7800. 

 

https://www.amazon.com/Converter-Yeeco-Regulator-Ajustable-Transformer/dp/B011EBSKK0

Edited September 6, 2019 by Mark loves Stella

[Obiw4n]

I think I've just fried my 2600 with 28v... I thought I was being clever you see by using a DC DC booster for a USB power conversion I was doing, I forgot to measure the volts coming out of that booster after I'd fiddled with it and before you could say "Fricassee'd 2600" It was goodnight Vienna from my ole Atari, anyway I'll nab another one for the guts... but I may need some advice, I was simply trying to make my 2600 USB powered, then I saw this thread about the colour circuit needing 8v so I bought the booster and poof... I made a muck of it, next time I thought to myself I'll just wire in 5V to the board and then ask you guys where the booster should go.

 

I bypassed the power regulator ( snipped the three pins, soldered the In & Out of the regulator together ) got the power switch working with it, I used a micro-USB breakout board which wired directly into the 2600's circuit board, I removed the old DC power jack input from the board and I had just enough space to install into the plastic case a nice female micro-USB port which then connected to my micro-USB breakout-board, If I had just wired it all up without the booster It may have worked ( without colours ) but in the end I restored the power regulator and the DC jack to see if it was dead and yup it's toast... just static & more static.

 

But where do I insert the 8v for the colour delay circuit ? please explain clearly as I'm a novice at this, thank you.

[+DrVenkman]

That was quite a wall of text …

 

If you’re determined to bypass the 9VDC input and wire in 5V directly, forget screwing around with any kind of “booster”. The output leg of the existing 7805 voltage regulator (pin 3) is the 5V DC source for the entire system. Assuming you’re keeping the existing center-positive 3.5mm input jack, remove the voltage regulator and wire the center pin from your jack to the location where pin 3 was from the VR. The existing internal circuitry of the 2600 voltage doubler circuit will handle the color potentiometer. 

 

But be damn sure you don’t even plug a 9VDC source back into that 2600 or you’ll destroy another set of chips! Put a label on the jack that says something like “MODIFIED CONSOLE: 5VDC ONLY!” lest someone pick up the machine in a few years without realizing it’s been changed. 

[Obiw4n]

On 7/15/2021 at 2:26 PM, DrVenkman said:

Assuming you’re keeping the existing center-positive 3.5mm input jack, remove the voltage regulator and wire the center pin from your jack to the location where pin 3 was from the VR. The existing internal circuitry of the 2600 voltage doubler circuit will handle the color potentiometer.

 

 

Thank you for your informative reply, I was actually going to take out the 3.5mm jack altogether and replace it with a micro USB panel mount so that would plug into my little micro-USB breakout board which I could then wire the output of into the spot where the 3.5mm jack was and power it that way ? any good would you say ?

 

I haven't yet tried this myself, but a friend also had the USB-power mod done and he reported that although he had colour on his big modern Samsung TV ( his 2600 also had a composite-out mod btw ) yet his old 14" Sony Trinitron was B&W, perhaps that colour pot needed tweaking, or the Sony ( CRT 1988 I think ) was being fussy or that mod wasn't up to the job of powering the board completely... odd, anyway I'll report back with some more results, but please If you could advise me further it would be a positive boon... and yes I used the word boon, cheers

[+DrVenkman]

If you're going to use a USB panel mount, you need to remember that it only supplies 5V DC, not the 9V DC the Atari expects. In that case, you absolutely need to remove the 7805 voltage regulator; those typically have an input range of 7.5V - 12V or so. The 5V available via USB won't work. Once the VR is removed, you should be able to add a jumper wire from pin 1 of the former VR location (the input leg) over to pin 3 (the output leg). After that, you can take your USB panel power pin and connect it to the trace where the former 3.5mm jack used to feed the 9V supply to the voltage regulator. 

[Obiw4n]

Worked a treat seemingly, at first the Space Invaders cartridge I tried was B&W but with a slight tweak on that colour pot on the board colour returned, I did a few on/off tests and it was fine also, I ran it for an hour with no problems.