PCE power input tolerance, and has anyone tried to mod a psu into a console?

cheezio · 04/14/2012, 10:31 AM

Hi, the power brick for my pc engine has a rate output of 9v 850ma, I am using the original Japanese one with a stepdown converter in the UK.
Both the psu and the stepdown are heavy old things and I would ideally like a single lighter solution.

Would a psu with an output of 9v 1A work ok? (there are a few of these cheap on ebay) Or does the supply need to be exactly 9v 850ma?
Also does the plug that goes into the PCE have a special name ? (just so I can be sure it fits ok)

Finally, out of interest has anyone ever tried to fit a small psu inside a pc engine? It would be nice to be able to just plug a stereo type lead in (the figure of 8 type) to the console

thanks!!

Frank_fjs · 04/14/2012, 11:00 AM

Just use a Mega Drive 1 PSU or equivalent, no need for a stepdown.

No dramas running a PSU with a higher Amperage.

What you do have to worry about is the plug size (fortunately the PCE uses a fairly common size) and more importantly, the polarity of the plug. The PCE expects a plug with a negative tip, which isn't common nowadays and using a PSU with reversed polarity will damage your console.

What you need is a PSU with the following specs:

DC 9V 1A (doesn't need to be 1A but these are more common - just get one with 650mA or higher)
Plug size: Outer Diameter 5.5mm; Inner Diameter 2.1mm
Plug polarity: (+)----(o----(-) | negative tip, positive outside

As mentioned, a PSU from a Mega Drive 1 will work, as well as one from a Master System 1, Master System 2, Game Gear (non US) etc.

SignOfZeta · 04/14/2012, 11:17 AM

The mA rating can be higher, but not lower, so yeah, 1A is good. From my experience you can run a Core Grafx on a PSU with as little as 355mA, but you might run into issues if you hook five controllers up to it. I'd shoot for at least 600. The IFU setups and Duos really need the 1A. When the laser moves from one end of the CD to the other it really sucks the power.

As for internalizing the PSU...come on. Be nice. This is the smallest system of all time and you want to cram a PSU in there? With a totally unshielded improperly heat sinked one, yes, you probably could, if you took out the RF module. I would be more of a stunt though and not something you'd want to put a lot of hours on as the heat buildup might get out of control.

thesteve · 04/14/2012, 05:43 PM

install a 5V brick and eliminate the 7805 regulator.
that will reduce heat

Yoder · 04/14/2012, 07:18 PM

One thing to keep in mind is that power supplies just deliver amperage based on what the unit needs...you can ALWAYS use a higher amperage PSU on anything. It's no different than taking $1000 to a yard sale just in case ;-)

IMO, if you find a switching PSU, you could easily build it in...and like Steve said, if it's 5V, just take off the 7805 and tie it in there. You can find a pile 5V PSUs that go upt to 2.5A. They weigh about 2 oz, so there isn't much to them inside there...and they're pretty eazy to crack open :-) The hardest part would be getting the female plug mounted in there.

cheezio · 04/15/2012, 06:05 AM

Thanks for the info everyone!

So if I were to bypass (remove) the 7805, a PSU internals like from this would be ok? (5v 1amp) :
wayback.ebay.co//UK-DC-5V-1A-Switching-Power-Supply-adapter-100-240V-AC-Promotion.

Does anyone know a good link to a reference diagram of the power area (around the 7805) of the PCE motherboard? I can only seem to find diagrams about the main chips when googling.

Also, found a cheap source of a `figure of 8` socket

-
wayback.maplin.co/figure-of-8-mains-power-inlet-with-switch-219900

Game-Tech.US · 04/15/2012, 10:42 AM

I did a project like this on a nes-101 a few years ago, using a very similar chinese switching p/s, it did work, though at the time I didn't have a scope so I didn't investigate the quality of the power being supplied to the board. I used the original power port and the wall adpater/power supply normally and just jumpered the traces necessary to make it work. Also, be leery of those cheap chinese power supplies, I buy them by the hundreds and there's always a few in each box that are crap and never work.

cheezio · 04/15/2012, 05:06 PM

Quote from: akaviolence on 04/15/2012, 10:42 AMI did a project like this on a nes-101 a few years ago, using a very similar chinese switching p/s, it did work, though at the time I didn't have a scope so I didn't investigate the quality of the power being supplied to the board. I used the original power port and the wall adpater/power supply normally and just jumpered the traces necessary to make it work. Also, be leery of those cheap chinese power supplies, I buy them by the hundreds and there's always a few in each box that are crap and never work.

Cool thanks for the link!
As luck would have it my old zip100 drive from 1999 has a very small psu that I just noticed is 5v 1.0A, and already has a figure-of-eight socket on it (its very light too, unlike my old epsom amiga zip drive one which was a big brick type psu that plugs into the wall).

Still looking for some pce circuit layouts to save me some time, but the zip100 psu looks like a winner to harvest power circuits from.

incrediblehark · 04/16/2012, 07:54 AM

good luck with the mod! would like to see pics when you get it finished

Yoder · 04/16/2012, 12:08 PM

The 7805 voltage regulator should be easy to find on the board. It will be right behind the power port. One leg for input, one for ground, and one for output. Carefully probe them with your multimeter to confirm. All 5V to the board comes through the 7805, so tapping in there should do the job. If you cut it off, you could just supply the 5V at the output post of the 7805, and I think you'll be fine. From my understanding, switching power supplies are regulated by the switching ICs, so you should get a stable 5V, if that's the case. Can someone else comment on this?

Another option would be to get a 6V or 7.5V power supply and just send it through the 7805 and that will ensure you that you'll get a nice regulated 5V, and the differential would be minimal so heat output would be lower than with the 9V adpater.

thesteve · 04/16/2012, 12:09 PM

all you need to know about the power circuits is the pinout of the 7805 regulator IC.
its the 3 wire part on the heat sink.
it takes 9V or more in and puts 5V out
other wire ground

cheezio · 04/17/2012, 04:33 PM

Thanks for the info everyone, that makes it a lot clearer.

In terms of power supply source, I just noticed my mobile charger is 5v 1a too (htc b250 type) which is even smaller than the zip power case.
So now I am pondering using the zip one OR the htc (smaller and newer) OR going for a usb socket on the PCE and using that together with the external htc charger (its so small and light only a bit smaller than a normal plug, and seems the logical choice as I have more flexibility if that part breaks externally).

Will have a think at the weekend on which approach to take!

Yoder · 04/17/2012, 08:35 PM

I'd go with the newer adapter...recent switching PSUs are pretty good and it will have more life left in it. You could use a USB socket, but USB spec is only 500 mA, I think. Of course, it would support it, but technically it would be incorrect to have that socket there...but who really cares if you're keeping it. As long as someone didn't try to power it with a PC or lower powered USB power adapter it would work fine.

Or to make things easier, why not just get a small 7.5V or 9V switching adapter and call it a day :-) I found one for my Genesis and it's great! Weighs a tenth of the original PSU. But I understand...I like projects too ;-)

cheezio · 06/02/2012, 08:11 AM

quick update - I cracked open an HTC phone charger, to see if it would fit ok inside a PCE and yes its small enough.
Problem is it has set live/neutral wires, so a figure 8 lead wouldn't work as the polarity could be plugged in wrong.
A cloverleaf style plug is just too big and stiff to try to mount - so I have decided on the following:

Htc charger unmodded to plug into the wall - then from that a usb to barrel cable (cheap from amazon) - then inside the PCE link the wires from the socket over to the IC 5v output leg and ground (so IC is bypassed).

Probably should add a fuse/diode in there too (like the ones inside the PCE).

Hope to have time this weekend to sort it out!

thesteve · 06/02/2012, 03:18 PM

the charger doesnt care about hot/neutral.
just be sure your input and output are isolated

cheezio · 06/05/2012, 10:41 AM

Thanks once again for the info thesteve!

I finally did the mod today, and plumped for using an external htc charger, that has a usb to barrel lead - then in the PCE I took out the black cube thing near the socket (sorry not sure what it was) that had 4 legs - and routed the live into the fuse as per normal. Then chopped the 7805 out and linked the input and output legs together - this way the power switch still worked.

All working fine after a quick test with Military Madness and R-type

Thanks again to everyone for their help!