Potentiometer in Neo 25 psu is fubar. Halp

Hey all,

Picked up a Neo 25 cab from a local recently and threw in a four slot. No go, psu worked, monitor worked but the 4slot would not start up. Tried a single-slot in there that I know is good (came out of my other cab), same deal. Nothing.

Checked voltage on the +5v pins, was getting 3.3v from the psu. Okay, I've been told by several users (channelmaniac in particular) that the four slots need around 5.1-5.2v to operate properly. Okay, I go to adjust the potentiometer on the psu.. oh, great, an empty hole.

So I unscrew the psu from the case and take it out, and I immediately hear a rattling sound. Must be the pot. I open up the casing, sure enough, there's the pot, ripped to shreds and broken clean off the board.

Pics are below.

Where can I get a replacement pot that will work properly with this psu? I figure the psu is still good, so I can just solder in a new pot and I am good to go, right?

If not, where the hell can I get a new (or used) psu? I searched a bit and I found that most people are chopping up Happ psu's or whatever to work.. not really interested in soldering a bunch of wires, thanks, so I'd like to avoid that if possible.

Thanks in advance for all the help!


Pic of the PSU. Hole in the top-left is where the pot should be.



Two different close-ups. Top left is where the pot should be on the pcb.




Pics of the pot. As you can see, the previous owner hired a bear or perhaps a woodpecker to perform the pot adjustment.

Are there any numbers or letters on the body of that pot?

Is the white part plastic or ceramic?

Maybe another forum member has one and can tell you what the resistance is.

RJ

Pot is all plastic as far as I can tell. Also no markings that I can see.

If any forumers have the same PSU and can measure the resistance for me as Ray suggested, I would be a happy camper.

Thanks!

Looks like the wiper track is intact, do you have an ohm meter ?

ttooddddyy said:

Looks like the wiper track is intact, do you have an ohm meter ?

Click to expand...

My DMM has an ohm fucntion, so yes.

I would like to replace the pot and keep the existing power supply, if at all possible...

Amusingly enough, I tried running another search and came across this:
http://www.neo-geo.com/forums/showthread.php?t=98323&highlight=happ+power&page=2

Same exact psu and problem I am having. Oh joy.

I may just bite the bullet, get a Happ PSU and re-wire... anyone have any recommendations on which one to use? I'm going to PM NGT and ask which one it was that he had... I was looking at the PSU's on Happ's site and it is not clear which ones have pots to adjust the voltage... anyone know?

Thanks in advance for the help, everyone!

Interestingly, there are numbers right on the face of the pot. Didn't even notice them! A user on another forum spotted them and had this to say:

grantspain said:

to match a pot you need to look at the number printed on it,i think your says 201 there its 2 0 and one x 0,that should be 200ohms
other examples 202= 2 0 and two x 0 2000= 2 kohms
401= 4 0 and one x 0 400ohms

Click to expand...

So it would appear that it is a 200ohm pot... we're getting somewhere! Now I just need to find a reputable source for one. Radio Shack is no good.

www.mouser.com

They even have datasheets on the parts so you can take measurements and find one that will fit the holes in the board.

There's a lot of options on there, not even sure where to begin.. just searching in the "potentiometer" category yields only a few things that will work, and this one is the only one that comes close:

http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsEGgLEzQVydsJegMEUPLmxDPlIXgwz/GA=

The feet aren't in the correct orientation, either.. could I just solder some wires to the pcb and the other ends to the feet and do it that way?

I think you want Mouser part # 594-63X201

It is Vishay part # M63X201KB40

Datasheet: http://www.vishay.com/docs/57027/63.pdf

You want the X not M part # (63X not 63M)

Thanks for the help, Ray! I am not the most technically-proficient person around (though I am not totally clueless!) and I could use the help.

My only concern now is looking at how the feet are oriented in the pic of that pot and the location of the holes on the pcb, wouldn't the adjustment screw face the wrong way? That is, it would face into the case of the psu and not toward the outside?

Going to order that pot and see what's what. Will update.

Just a quick update - got it fixed! The pot worked perfectly, aside from the fact that it sat facing backwards--that is, the adjustment screw faced into the PSU, rather than toward the outside due to the orientation of the feet. But it worked perfectly. Got it set to 5.09v and my MVS boards work fine!

Thanks to grant and channelmaniac for the excellent information!!

WOOHOO!

Glad I could help

Thank you, Ray. Board works perfect, BTW.

You're quite welcome! Enjoy the 4 slot board

Oh, and thanks for the trader rating. I left you one too.