astro city PSU

[kenzo42]

hi everyone, i recently purchased an astro city and i'm planning on placing a dreamcast in it, for the time being.

b/c i won't be using any boards, i'd like to remove the psu. however, the wiring doen't seem to follow bob roberts basic wiring chart by splitting from the distributor to 1) the psu 2) the monitor. i'm new to this so i hope you all can help. here's the psu and wiring coming from the wall outlet:

http://pg.photos.yahoo.com/ph/liu_feng_yi/detail?.dir=/cb97&.dnm=46eb.jpg&.src=ph
http://pg.photos.yahoo.com/ph/liu_feng_yi/detail?.dir=/cb97&.dnm=2369.jpg&.src=ph

the single power wire coming from the noise filter lead to the psu. would removing the psu make the machine inoperable, since the monitor power actually has to go through the psu? will i have to wire the power line directly from the noise filter to the monitor in this case, with some sort of switch built in?

i always thought monitors weren't powered through the psu.

any recommendations on how to get this done?

thanks guys,
kenzo

[Ken Layton]

Holy crap! 

I've never seen nor heard of this machine.


 It looks like this is a special power supply particular to this game AND cabinet. Appears that part of the monitor circuitry is jacked through this unit. My advise is if you want to modify this for something else, DON'T. Looks like this would be very involved. I could probably do it, but the entire machine would have to be here in front of me and with a full schematic wiring diagram in hand.

[Dave_K.]

Wow!, Ken Layton stumped!  Thats pretty rare.   He probably just isn't familiar with japanese cabs.   

Hey Kenzo, I think I PM'd this advice to you before, but if you remove the PSU, then you will need to get an isolation transformer  110V-to-100V  to power the monitor.   Thats why the monitor is powered through the PSU.  I'd suggest just keeping the original PSU.  Yeah, I know that no load on the +5 and +12 is not good for it, but it will be awhile before it goes bad (if at all).

My Astro City 2 thread is a couple below yours.

[kenzo42]

thanks for the replies guys.

dave_k, would i need BOTH a step down converter (120v ->100v) + isolation transformer to get this thing going? i already bought the step down converter.

dave_k, did you ever think of an external 3.3v power source to power your dc?

thanks.

[Dave_K.]

You can actually buy an isolation transformer that does the 110v to 100v conversion for you.  So that would be all you need.

Good question on the v3.3.  I was thinking about either wiring my own +5V to 3.3V regulator circuit, or maybe see if there are any 3.3V DC adapters at a local electronics outlet.  I'm just not sure how many amps are required.

Anyway, don't let this hold you back from starting your project.  Just use the PSU as is, and plug the DC into an extension cord that runs out the back of the cab. 

[kenzo42]

1) since i already purchased the step down converter (120 -> 100v), would using a 1:1 isolation transformer be the correct one to use?

2) IF i've overlooked the isolation transformer in my cab, and i place another one in it (total=2), what could possibly be the worst outcome?

3) where could i get a 120 -> 100v isolation transformer anyways? i've looked couldn't really a place.

thanks

[Dave_K.]

I'm not really sure if you still need an isolation transformer if you already got a stepdown converter.  I'd think its basically the same thing...but I could be wrong.  If your cab is plugged into the converter, and it doesn't use a 3 pin plug, then I'd think its isolated.  I could be wrong here...maybe Ken Layton can chime in.

If you still need one, then #1 is correct.  As for sourceing these parts you can try mouser electronics (they will send you a free catalog).