Best 12V DC source in Sega backbox (tl;dr)

[cooldan]

Apologies in advance for the long boring post. I will try to break up the tedium with some pictures of dogs (and a slug) that look like people.



Here it is, the boring bit - I hate the fluorescent tubes in backboxes so I finally decided to do something about it and replace with some flexible LED strip instead.
So I bought a 5m roll that I figure should be enough for 3 or 4 games, and a few connectors, and now I just need to find a source of the 12V required. Then I looked in the manual and that just opened up a can of worms for me:



I started off by just looking for where 12V was mentioned in the schematics and found several places on 4 different boards which I jotted down on the notepad in the picture - some connector pins but also on a couple of fuses and on a bridge rectifier.

The power supply output CN2pin7 blue wire looks a good candidate, and presumably that is also the source of the +12V blue wire on the DMD control board. The other choice is J16pin2 grey-white or pin3 grey-red on the I/O driver board.



So I started looking at the I/O board schematic and it seems that the +12V going to J16pin2/3 comes from bridge BR3, which has two inputs and two outputs. Outputs are +12V DC and -12V DC, inputs are from J17 pins 2 and 3, 19V AC from the transformer via fuses F8 and F9 - but as written, it goes into the fuse as +19V AC and comes out the other side (at the bridge) as +9V AC. So WTF happened there? Can fuses be used to drop voltage?



So yes, here are my questions for the knowledgeable: which of the above would you use as a 12V source for this LED strip? Or none of the above and something else instead? And how did that transformer 19V AC turn into 12V DC, and is it a clean enough source?




And which of my looky-likey pics is the best? Putin, right?

 

[aaronhicksuk]

Well the all the extra pictures have made your post quite difficult to read and refer back to but.....

I'd take your 12v from J16 Pin 3 on the power driver board because it was only intended to be used for an optional printer and I doubt you'll ever use that! Pin 2 supplies the audio part of the CPU/Sound board. It doesn't really make that much difference though as they are both fed by the same bridge rectifier. If you take power from here then you really need to add a suitably rated fuse to protect the circuit though. The 5A Slo Blows at F8 and F9 before the bridge rectifier don't offer enough protection imo.

Fuses don't lower voltage, you put 19v in and you get 19v out, so the 9v on the schematic is a typo. Its the job of the bridge rectifier to convert the 19V AC from the transformer into 12V DC, and yes its definitely a clean enough source of power.

Was it not possible to get 6.3v LED strips? Then you could of just connected on to one of the GI circuits.

P.S. - A lot of the looky likey photos are quite close resemblances, but I reckon either the Putin or the Snoop Dogg are the best.

 

[cooldan]

Cheers Aaron. I went for 12V as that's what I was recommended to get, but I see your point. Do they make 6.3V LED strips then? And if they did, where would I attach it to snake some GI power from? And why would that be preferable to a 12V source?

There's no GI circuitry in the backbox, if there was then I wouldn't need to replace this ****ing tube - it also irritates me that it's on whenever the machine is plugged in, even when it's not switched on, so I'm looking forward to fixing that nonsense too.

How - and where - do I add a fuse when I hook up to pin 3 as you suggest?

I'm so pleased that Trump finally got his comeuppance so I will probably be posting more derogatory antiTump spam soon I expect.

 

[aaronhicksuk]

Yea you can get 6.3v LED strips from Comet: http://www.cometpinball.com/MATRIX-50-SMD-5050-6-3V-LIGHTED-STRIPS-p/50smd6.3vstrip.htm.

With these you could just attach them straight on to the GI circuits at J15 as evenly as possible, being careful not to load them up too much. This isn't likely to be a problem if the rest of the playfield GI has been converted to LED but you might be in trouble if using incandescent lamps. The main advantages of going this route is the backbox lighting would turn on/off with the rest of the playfield GI instead of just being switched on permanently and these circuits are already suitably protected by additional fuses as standard.

The 12v rail may have more available capacity given that there was an option to add an optional printer so its not a bad option. You just need to fuse whatever you connect on to it to be on the safe side.