DC voltage to a SNES/SFC?

Max P. · Post by **Max P.** » Thu Nov 30, 2006 11:57 am

Hello all.

First post, very pleased to find this place. I have been checking inside the circuit boards of a SNES and a SFC to check out some ideas.

(I am in the UK where our mains power supply is 220v.)

On my US SNES I use a dedicated UK transformer which according to the specification on the label outputs 9v DC - which is I believe the correct voltage for the SNES. However when connecting a multimeter to the SNES board the supplied voltage measures around 12v.

On the Japanese SFC I use a stepdown UK transformer with the original Japanese 110v unit. However measuring the voltage on this one's board it comes out at 16v! despite the spec on the transformer stating 10v DC.

1. Is this anything to worry about? Both machines have been used for 15 years without problems...

2. With this in mind if I wanted to connect some illuminating LEDs (for inside a new clear housing) by tapping this power from the board I guess I would need a resistor for each one calculated by using the voltages above?

3. If I wanted to use a PS ONE screen and take the power for that from the SNES baord also how would I do this and get the right voltage?

Many thanks for any help.

ATOMICMAN · Post by **ATOMICMAN** » Thu Nov 30, 2006 12:01 pm

the older the system the higher tolerance for higher or lower voltage.

it takes a good amount to kill a snes with just voltage alone.

you shouldnt have any problems hooking up a few leds.

Post by **marshallh** » Thu Nov 30, 2006 1:12 pm

The consoles should be fine - they're made to handle input voltages like that.

The SNES circuitry runs at 5v. However, this is regulated by a chip called a 7805 so that no matter what voltage you put into the 7805, you always get 5volts out.

You can run a 7805 off any voltage from 7.5v to 20 or so volts without a problem. It simply discards the excess voltage as heat.

If you want to wire LEDs in, it's best to run them off the 5v output of the 7805.

Max P. · Post by **Max P.** » Thu Nov 30, 2006 2:27 pm

Thanks for the quick replies.

I had measured thevoltage before the chip (doh!) - measured from the output it is a very lovely 4.98

Would it be necessary to use a resistor for each led (standard 5mm leds) and if so can anyone tell me the value please?

Where (and how ) could I get the correct voltage for the PSone screen? I am not really building a portable - just a re-cased SNES with built in screen.

ATOMICMAN · Post by **ATOMICMAN** » Thu Nov 30, 2006 2:47 pm

psone runs off 5 volts i believe so you can use the normal power off the snes.

as for resistors for the leds, depends on what kind of leds you plan on using.

Max P. · Post by **Max P.** » Thu Nov 30, 2006 3:18 pm

That make things simple. This may seem a daft question but is there any problem tapping the 5 volt output for the PSone screen, ie is there enough power there to go round?!

The leds are standard 5mm ones as below. Do I only need one resistor from the 5v supply and then connect this supply to all the leds (6 or so) together?

http://www.maplin.co.uk/Module.aspx?Mod ... &doy=30m11

or these:

http://www.maplin.co.uk/Module.aspx?Mod ... &doy=30m11

lifeisbetterwithketchup · Thu Nov 30, 2006 3:39 pm

ATOMICMAN wrote:psone runs off 5 volts i believe so you can use the normal power off the snes.

PSOne screen takes ~7.5 volts. You could use a 7808 or a switching regulator to get the correct voltage.

To post above: IIRC, only 3mm LEDs will fit in a PSOne screen.

Max P. · Post by **Max P.** » Thu Nov 30, 2006 4:04 pm

Just to clear up the led thing (sorry for any confusion) - these are nothing to do with illuminating the PSone screen - they are simply there as 'decoration' to illuminate the clear casing I plan to use. (like a modded PC case). As I will be using mains I will keep the standard PSone bulb illumination.

Re' the power input - I think the input on a PS one screen is 7.5v to the 7805 voltage regulator that then outputs 5v. So...if I am already using a regulated 5v from the SNES board I guess I can just solder this supply to the output pointof the PSone 7805...? Anyone confirm?

lifeisbetterwithketchup · Thu Nov 30, 2006 8:00 pm

No. Part of the circuitry (video encoder) requires the 7.5 volts.

Max P. · Post by **Max P.** » Fri Dec 01, 2006 2:38 am

Thanks - so I would need to take the power from the SNES 7805 input and feed it to the PSone 7805 input?

Or would this not work as the input is then around 12-16v (see my opening post) and the PSone only wants 7.5 volts?

I don't want to end up with two seperate power supplies - how can I step the 12-16v down to 7.5 for the PSone?

Or could I use the PSone power supply for the SNES even though it should be 9v not 7.5?!

Post by **Skyone** » Fri Dec 01, 2006 3:57 am

*smacks head*

The PSOne Screen needs 7.2v minimum.

The SNES needs 7.2v minimum.

Just get a 7.2v-8.5v source and hook it up to the inputs of both. That means the "7.5v Input" line of the screen and the switch or the input of the the 7805 on the SNES.

Check TI.com, Digikey.com and Linear.com for regulators.

Max P. · Post by **Max P.** » Fri Dec 01, 2006 4:44 am

Thank you! I will just use the PS power supply then - make it very simple.

Can I just ask another sort of related Q?

How do I re-wire the SNES reset switch? I want to removed the existing switch and re-wire to a standard type switch ('push to break' I guess?) to be mounted on the new case. Unsure which of the solder points to use on the MOBO.

Thanks again.