checking polarity without voltmeter

[themctipers]

i need to check the polarity of a power supply.

the power cables are both grey, so can't tell from that.

it's 19v 3.5a, DC.

 

i don't have a spare electronic to see if it blows up. i don't have a voltmeter. 

 

if it matters, im going to be using this with a small amp, and it doesn't have reverse polarity protection.

[Electronics Wizardy]

you have a led?

 

You can normally tell if you can see the pcb and look at the caps and diodes.

[themctipers]

Just now, Electronics Wizardy said:

you have a led?

 

You can normally tell if you can see the pcb and look at the caps and diodes.

no.

 

i can't take apart of the power supply.  

[Windows7ge]

5 minutes ago, themctipers said:

i need to check the polarity of a power supply.

the power cables are both grey, so can't tell from that.

it's 19v 3.5a, DC.

 

i don't have a spare electronic to see if it blows up. i don't have a voltmeter. 

 

if it matters, im going to be using this with a small amp, and it doesn't have reverse polarity protection.

Well. If you can find something that's reference to ground and short each wire to it one at a time one will make a spark and the other won't that'll tell you which wire is live and neutral. You can use the neutral port in any wall jack.

[themctipers]

5 minutes ago, Windows7ge said:

Well. If you can find something that's reference to ground and short each wire to it one at a time one will make a spark and the other won't that'll tell you which wire is live and neutral. You can use the neutral port in any wall jack.

if i short the power supply, it'll be broke and not work anymore.

 

i don't have any reference to anything. just 2 wires, and +/- for the other side which is going to be using the power.

[Windows7ge]

1 minute ago, themctipers said:

if i short the power supply, it'll be broke and not work anymore.

 

i don't have any reference to anything. just 2 wires, and +/- for the other side which is going to be using the power.

You misunderstand. Shorting neutral to live could damage the power supply that's not what I'm saying doing that wouldn't tell you which is which. If the power supply gets wall power you can touch one wire at a time to the neutral pin in any wall socket (not safe but it'll tell you which is live and it shouldn't harm the power supply). Don't use the ground plug though. If your house has a GFCI shorting the live wire to earth could kill power to the entire house lol.

[themctipers]

1 minute ago, Windows7ge said:

You misunderstand. Shorting neutral to live could damage the power supply that's not what I'm saying doing that wouldn't tell you which is which. If the power supply gets wall power you can touch one wire at a time to the neutral pin in any wall socket (not safe but it'll tell you which is live and it shouldn't harm the power supply). Don't use the ground plug though. If your house has a GFCI shorting the live wire to earth could kill power to the entire house lol.

that sounds... really dumb  (my understanding is that you want me to short any wire to the neutral pin (but we have AC..?) )

 

[mpsparrow]

Ask a neighbor if you can borrow one... or buy one for $15 off of Amazon. Worth spending a few bucks if you ask me to save having to buy a new PSU.

[themctipers]

Just now, mpsparrow said:

Ask a neighbor if you can borrow one... or buy one for $15 off of Amazon. Worth spending a few bucks if you ask me to save having to buy a new PSU.

this is smart, yes

but im linus, and ghettoing this

 

i dont have prime, and shipping takes a week. i don't want to wait a week for amazon shipping (no prime) and my neighbors don't even speak english/cantonese.. 

[mpsparrow]

2 minutes ago, themctipers said:

this is smart, yes

but im linus, and ghettoing this

 

i dont have prime, and shipping takes a week. i don't want to wait a week for amazon shipping (no prime) and my neighbors don't even speak english/cantonese.. 

All your neighbors don't speak English... sounds like you are just making excuses. Do you have a hardware store near you? They probably sell them for $20.

[Windows7ge]

1 minute ago, themctipers said:

that sounds... really dumb  (my understanding is that you want me to short any wire to the neutral pin (but we have AC..?) )

 

It is dumb. I know it's dumb, but not having proper equipment results in dumb improper solutions.

AC or DC either should want the fastest path to earth to complete a circuit. Connecting a neutral wire to earth won't do anything. Neutral is allowed to complete a circuit but it does not supply the power. Connecting a live wire to earth is effectively a short circuit because their's no load. This will result in the wire getting hot or sparking telling you which wire is which. So yes. It is dumb and not recommended but it'll give you your answer quickly and free...but if you short either wire to live the PSU might explode and you could go flying across the room. Hence "dumb".

[themctipers]

Just now, mpsparrow said:

All your neighbors don't speak English... sounds like you are just making excuses. Do you have a hardware store near you? They probably sell them for $20.

chinese neighborhood, poor english, they speak mandarin and i speak cantonese.

 

no.. if i was able to (quickly) this thread wouldn't exist.

[mpsparrow]

3 minutes ago, themctipers said:

chinese neighborhood, poor english, they speak mandarin and i speak cantonese.

 

no.. if i was able to (quickly) this thread wouldn't exist.

Just get the proper equipment please. Risking frying a PSU, yourself, and possibly your house by trying some bogus lick this wire is just stupid.

[themctipers]

Just now, mpsparrow said:

Just get the proper equipment please. Risking frying a PSU, yourself, and possibly your house by trying some bogus lick this wire is just stupid.

i wanted to see my options before i do anything (see if theres a 'secret hack' or something)

 

it sounds so stupid, even i wouldn't do it..

[Windows7ge]

6 minutes ago, themctipers said:

i wanted to see my options before i do anything (see if theres a 'secret hack' or something)

Yeah, without the proper equipment every other option is bogus and risky.

 

As i exampled.

[mpsparrow]

Just now, Windows7ge said:

Yeah, without the proper equipment every other option is bogus and risky.

Especially if you are not an electrical engineer or something.

[Windows7ge]

3 minutes ago, mpsparrow said:

Especially if you are not an electrical engineer or something.

I'm more confused by the fact this two wire unit doesn't have color coded wires. Was the original device designed with polarity correction so it didn't matter if the PSU was wired backwards or...?

[mpsparrow]

1 minute ago, Windows7ge said:

I'm more confused by the fact this two wire unit doesn't have color coded wires. Was the original device designed with polarity correction so it didn't matter if the PSU was wired backwards or...?

Made by a colorblind person I guess

[themctipers]

5 minutes ago, Windows7ge said:

I'm more confused by the fact this two wire unit doesn't have color coded wires. Was the original device designed with polarity correction so it didn't matter if the PSU was wired backwards or...?

yeah,  it was

 

3 minutes ago, mpsparrow said:

Made by a colorblind person I guess

or anyone who would fuck around with a power supply would have a fucking voltmeter

[Windows7ge]

4 minutes ago, themctipers said:

or anyone who would fuck around with a power supply would have a fucking voltmeter

You mentioned before that you can't open it. Why? Weird screw? Held together by clips? Glued?

[themctipers]

Just now, Windows7ge said:

You mentioned before that you can't open it. Why? Weird screw? Held together by clips? Glued?

glued with superglue

[bob345]

I would just get a volt meter. You can easily get one for less than $5. The only other way i can think of that doesn't involve an led would be to try plating something in an electrolyte solution to determine the polarity. the setup would be something like this using a copper penny and a quarter(if you are in the us). For an electrolyte you can just use water and baking soda. If you set it up and no plating happens, then the polarity was backwards. If you reverse it and the plating starts then the plated conductor would be your common and the plating conductor would be the positive.

[themctipers]

Just now, bob345 said:

I would just get a volt meter. You can easily get one for less than $5. The only other way i can think of that doesn't involve an led would be to try plating something in an electrolyte solution to determine the polarity. the setup would be something like this using a copper penny and a quarter(if you are in the us). For an electrolyte you can just use water and baking soda. If you set it up and no plating happens, then the polarity was backwards. If you reverse it and the plating starts then the plated conductor would be your common and the plating conductor would be the positive.

if i was able to (quickly) this thread wouldn't exist.

 

[Windows7ge]

Just now, themctipers said:

glued with superglue

Ah, dremel the SOB and superglue it back together when you're done.

Even if you could get it open I get the feeling they probably half-assed the silkscreen. It probably doesn't identify +/- on the board. You'd have to trace the circuitry to determine which is which. If you did that though I'd remove the wires and solder on color coded ones after for future proofing.

[themctipers]

Just now, Windows7ge said:

Ah, dremel the SOB and superglue it back together when you're done.

Even if you could get it open I get the feeling they probably half-assed the silkscreen. It probably doesn't identify +/- on the board. You'd have to trace the circuitry to determine which is which. If you did that though I'd remove the wires and solder on color coded ones after for future proofing.

ill just not attempt it and lose my speaker's usage for a week, ill be in quebec anyways