Theoretical 2600 arcade machine

[sethbramwell]

Hi everyone,  theoretical question here... I'm attempting to build a bartop arcade machine that will play 2600 carts using the motherboard of an old 2600 I had in horrible shape (And before anyone asks why i would do such a thing, it's just a see-if-I-can project that was inspired by a post in the AA Facebook group).

 

Big question is this: I will be integrating a small LCD screen with an AV mod to the main board and an amplifier chip that requires 5 volts. Is it possible to use a 12v power supply to the 2600 main board? I would be splicing off of that power supply to the screen and including a voltage regulator to drop it to 5 volts to run the amplifier circuit. I don't want to try just leeching off the 2600 due to the amperage requirements.

 

From what I have read on the boards, I believe that a 12 volt power supply would still be within the tolerance for the built-in voltage regulator on the 2600 board. In theory can handle up to 35 volts but I would never push it that high. Obviously I would also use a higher amperage 12 volt power supply as it will be running more than just the 2600 board. Any thoughts?

[+Stephen Moss]

A 9 volt supply would be best because that is what the 2600 is designed for, as you say the regulator in the 2600 can an input up to 35 volts so in general using a 12V DC supply will be fine as the regulator will still output 5V and the voltage of the input capacitors will be at least 16V.

 

There are however a couple of caveats though...

1) At 500mA the extra 3 volts will mean an extra 1.5 Watts of power being dissipated in the regulator, this could potentially cause the regulator to go into thermal shutdown periodically depending on how much spare power dissipation capacity the ground plane heatsink of the PCB has to prevent the regulator heating up, consequently you may want to consider adding additional heat sinking.

2) If you are using an unregulated/stabilised power source (output voltage when not power something it higher that that specified) and are not taking the specified current from it then the output voltage will likely be higher than 12V, thereby increasing the extra power dissipation in the 2600's voltage regulator further.   

[sethbramwell]

6 hours ago, Stephen Moss said:

A 9 volt supply would be best because that is what the 2600 is designed for, as you say the regulator in the 2600 can an input up to 35 volts so in general using a 12V DC supply will be fine as the regulator will still output 5V and the voltage of the input capacitors will be at least 16V.

 

There are however a couple of caveats though...

1) At 500mA the extra 3 volts will mean an extra 1.5 Watts of power being dissipated in the regulator, this could potentially cause the regulator to go into thermal shutdown periodically depending on how much spare power dissipation capacity the ground plane heatsink of the PCB has to prevent the regulator heating up, consequently you may want to consider adding additional heat sinking.

2) If you are using an unregulated/stabilised power source (output voltage when not power something it higher that that specified) and are not taking the specified current from it then the output voltage will likely be higher than 12V, thereby increasing the extra power dissipation in the 2600's voltage regulator further.   

Thank you for your input!  I appreciate the caveats and your detailed explanations.  I like the idea of adding a small heat-sink on the regulator regardless of anything else.  I believe I have some small ones from Raspberry Pi projects if you feel one of those might work atop the regulator.  

 

As for a power supply, I would definitely use a regulated power supply.  I have some nicely stabilized ones that consistently output 12V, though I had not considered the potential danger of an unregulated one.  Thanks again for your help!

[+Stephen Moss]

I don't know what type of heat-sink you have but, ideally what you need is one for a TO220 package, preferable with a hole for the screw, like this, which will probably suffice. Place it between the regulator and the PCB, although you may also have to replace the regulator if the legs have been cut too short to re-solder once the heat-sink is in place.

 

You could use heat-sink compound but I find it messy and expensive as what is left in the tube usually sets hard after a few months and becomes unusable, I prefer thermal pads like these, I may be wrong but as I recall the PCB heat-sink area is either connected to ground or not connected to anything, the pads I linked to (as an example) are electrically insulating so should be fine regardless of where the PCB heat-sink area is connected.

If you get the electrically conducing version of the pads then the PCB heatsink area must be either open circuit or connected to GND otherwise you will have a short circuit where you do not want one.  

[Video]

Well if your doing a cabinet, even a bartop type, you should have enough space for a more traditional power bar to hook up however many psu you need.

 

If course, sounds like your going into heavier modding, and it could be cool to have a single switch to power in the system an display at once.

 

May not can handle it, but could the display mooch off the 5v power that runs the cart, or would that over tax how much power the cart port outputs?

[sethbramwell]

9 minutes ago, Video said:

Well if your doing a cabinet, even a bartop type, you should have enough space for a more traditional power bar to hook up however many psu you need.

 

If course, sounds like your going into heavier modding, and it could be cool to have a single switch to power in the system an display at once.

 

May not can handle it, but could the display mooch off the 5v power that runs the cart, or would that over tax how much power the cart port outputs?

I was hoping to avoid a power strip and use a single power supply.  I already built a cab based on the components I had planned to use. I was planning to use  a standard 2600 psu and feed the display by tapping the 9v line before the voltage regulator, but between the display and the sound chip I was worried about insufficient amperage/power.

[Voxel]

If it goes ahead I'd like an update on how it turns out.

 

Another method of dropping the voltage is to put resistance in line before the regulator and something like this (with higher resistance) lets you tweak the output to match what your regulator is comfortable with:

https://www.ebay.co.uk/itm/Ceramic-Tray-Wire-Wound-Variable-Resistor-Rheostat-100W-10-Ohm/311061066695?epid=1239242664&hash=item486caf33c7:g:X6IAAOSwhgxeoBLi

 

I have similar one knocking around and it's big and heavy.

 

Cabinets can generate a bit of canned heat so I guess you'll want to plan good airflow/extraction which would also help keep your regulator circuit cooler.  The display in particular will want venting.

[sethbramwell]

47 minutes ago, Voxel said:

If it goes ahead I'd like an update on how it turns out.

 

Another method of dropping the voltage is to put resistance in line before the regulator and something like this (with higher resistance) lets you tweak the output to match what your regulator is comfortable with:

https://www.ebay.co.uk/itm/Ceramic-Tray-Wire-Wound-Variable-Resistor-Rheostat-100W-10-Ohm/311061066695?epid=1239242664&hash=item486caf33c7:g:X6IAAOSwhgxeoBLi

 

I have similar one knocking around and it's big and heavy.

 

Cabinets can generate a bit of canned heat so I guess you'll want to plan good airflow/extraction which would also help keep your regulator circuit cooler.  The display in particular will want venting.

Thanks for the tip.  Upon consideration, I may just seek out a regulated 9VDC supply with a 1A rating and use it to drive the display and the main board.  I believe I can tap into the 5V line from the board to run the sound chip like I run the AV mod chip. 

 

I'll definitely post as things develop.  The display is a small (7 inch) display that I used on a previous project as an Atari driving game emulator as shown in the attached pics.  I recently moved and decided to dismantle the driving cab as it was getting unreliable and I wanted to do more with the screen.  As small as it is, it did a decent job displaying the games.  As you can guess from this, the cab itself is going to be pretty small.  I was in the process of building it when I messed up the board I was using.  Now I'm waiting on a new one from a trashed unit.  

[Video]

That's pretty cool. Good luck with your project, keep us posted!