John's Arcade Forum - Classic Arcade and Pinball Collecting and Restoring Discussion Forum - RETRO MAME - Nintendo Vs Forum

I'm a few months into a Galaga restore, home stretch. When I got it the old power supply was in place but it had been converted to use a switching power supply. To simplify things I decided to remove the old power supply PCB and transformer, following http://www.arcadeshop.com/gal-tips.htm. Things are going well, but I noticed that I’m getting continuity on both AC outputs of the remaining isolation transformer. Is this normal or do I have a short somewhere?

Also, regarding the larger connector to the old power PCB, arcadeshop said:

- Attach ALL red and the one white wire to the +5 on the PS
- Attach the orange wire to the +12 on the PS
- Attach ALL yellow wires to ground

Mine are all yellow and two white, though some of them have stripes. Likely there were several variations of wire color in these, but I’m not sure quite what to do. I checked continuity on a couple and found one yellow to be ground, and one white to be ground and coin 1.

http://jessiejohnson.net/arcade/2015-09-15-galaga-old-ps.jpg (this won't help)

So it seems continuity is normal on those AC outs. Also the rest of the wiring instructions were right other than one solid white I had which required ground, not 5v.

I'm not 100% sure I know where you're talking about reading continuity, but WITH THE MACHINE UNPLUGGED, if you are testing continuity on both connections of a secondary coil, you will have low ohms, and will show continuity.  Do not test continuity there with the transformer "hot" because this will be the 120v output, and you'll blow up your meter..

The isolation transformer has two outputs (black and white) coming out on top. It's there that I happen to touch them and found continuity (with game unplugged).

I've metered off AC many times -- I wouldn't think 120v is enough to blow it (or it's internal fuse).

A good multimeter should be able to survive 400V inputs into any mode. But i wouldn't trust a $20 meter from walmart. I am still not sure what you are trying to do with your meter and the transformer.

I have the same Fluke as John.

In removing the old Galaga PS components and testing my work I just happen across this continuity question on the iso trans. In any case it's working, and a friend with a similar setup also had continuity so I guess it's normal.

DEFINITELY correct, IF you're on voltage mode, but if you're on a resistance measurement / continuity mode, and hit 120vac, I would expect it to pop...  Never done it myself, but I wouldn't expect it to handle that..  I didn't mean to imply it couldn't handle it on VAC mode..

Ah right, and good to know!

a GOOD meter will not explode under any situation. a GOOD meter will continue to function even if you put high voltage into any mode. I can plug my meter into the mains and try to measure its resistance or capacitance with no ill effects.

What about one's tongue -- is that still considered poor practice?

Asking for a friend.