Can someone explain to me +5v, -5v, and +12?

enix2093

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I get the general idea of it, and I know that so far in my experience most 90's arcade units use +5v and +12, but what exactly does the -5v do?

I guess more specifically what I'm trying to get at is that my Konami cab has multiple games in it, and all of the manuals I've read for the Konami ones all say NOT USED for the -5v slot on the JAMMA and on the power unit...but I have NBA Jam also in my cab, and it's manual shows the -5v being used. I haven't had any issues with it NOT being hooked up, because it isn't currently...

...BUT what I want to do now, is add in Time Killers into my machine which REQUIRES the -5v to function. So, my actual question would be: Does anyone know if using the -5v will blow up or damage my Konami boards or my Capt. America board? Obviously NBA Jam should be fine since it suggests the -5v in the manual.

I would still like a general breakdown of what the -5v does too...

Thanks guys.
 
It seems to me that all the games you mention are Jamma conversion class games. In general +12v is used for the coin counters and sometimes the sound amp circuit. -5v is usually used in the sound circuit as well. Jamma games should work fine if the -5v is hooked up even though it may not be used in that game. To be sure, just look at the edge connector of the pcb. Pins E and 5 are the -5v. Usually, if the -5v is not needed, there will be a pad w/ no trace connecting it to the rest of the board. Since I don't have the schematics I couldn't tell you 100%.
 
I'll be damned...YOU'RE RIGHT. They all have a dead pin there for the -5v. Cool.

Ok, well one last question then...and this will sound stupid because I'm no electrician, but does the -5v need a fuse? My +12 and +5 both have fuses between the power unit and the JAMMA connector. I assume yes, but no use in wasting money if it's not needed.
 
I also have a question about fuses...The one from my +5v is "4A 250V 312", the one from my +12 is "1A 250V 320"...is that the threshold or is that how much throughput they support?

It seems that since the +12V is 2A and the +5V is 5A, I'd want the fuse to match that (?).
 
The important features of fuses is to match the correct type: slow blow vs fast blow

Next is to match the correct amperage. The voltage in not significant in this case.

ken
 
Ok, but what would the "correct" amperage be in this case? Do I undercut it by 1A like the fuses currently installed, or do I match is exactly, or overshoot by 1A? All of mine are fast blow.

Mind you, I inherited my cabinets so aside from learning how to wire buttons, joysticks, JAMMA, and slap in boards and stuff, I'm relatively clueless to electrical things related to arcades and power usage.
 
I wouldn't worry with the fuses. If they are working then leave 'em alone.

If you want to put in a game board that draws more current then you may need to replace them. Otherwise, I wouldn't touch 'em.

+5v runs your TTL and CMOS logic on the game board. It also runs the op-amps on most game boards.

+12v runs your audio amplifier and rarely the op-amps on a board. I've also seen it run the video amplifier section but that's pretty rare. It also runs some older EPROMs (TMS2716... 2708...) and older DRAM (4116)

-5v is used for old old chips such as 4116 DRAMs and for op-amps in the audio section.

RJ
 
Ok, well my issue is that I need to know what kind of fuse I should get for the -5v (1A).

Would a 1A 250V suffice?
 
If you wish to fuse the -5V line...

A fuse is there to blow (go open) in the event that something in the circuit unexpectedly draws excessive current. The idea is that the fuse will blow before burning up something important/valuable elsewhere. Even PCBs that use -5V (and as you've seen, many don't even use it at all) very little current is drawn. You might look at your power supply to select a maximum fuse value. For example, I've got a PS that's rated for -5V @ 0.5A and another -5V @ 1A. You probably don't want to pick a fuse rating any higher than the max current the PS is rated for. You can probably safely choose a lower current rating, too. In all likelihood, the actual current draw on the -5V line (on PCBs that use it) is in the mA range. You'd probably be hard pressed to find a fuse that would ever blow during normal operation on the -5V (i.e. I doubt an 1/8A fuse would blow). So, I might recommend finding your power supply's maximum current on the -5V, and fusing say half of that.

That said, the whole thing is a bit of a mountain out of a mole hill.
 
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