Bench power supply questions (noob)

[Jay]

Hi Folks,

I got the PPS2116A power supply and am having trouble getting magsafe plugs to work with it.
The magsafe cable only has two wires in it, one is + and one is GND, when I connect it to the PSU and set the Voltage and Amps as printed on the original power brick the cable was attached to... no magsafe light, no charge, nothing. The Mac works fine (using a beater MBP in case I blow it up) and with another normal charger, no issues.

Up to this point, any mistakes I've made in connecting, Voltage or Amps setting?

No experience with an external power supply so very much still in the learning phase. Any help appreciated

 

[Alan.L]

cut another MagSafe cable ?

white/grey cable is negative. black is positive.

 

[Jay]

The cable works, took it from a charger that i used on that same Mac just minutes before.
There's a white shielded cable in the center with a metal mesh woven around. I assumed that mesh was ground and the core was Voltage. There's no black.
This is a 85W Magsafe 1 with L-connector.

 

[dukefawks]

There is nothing more to this, only the shield and center conductor. Measure voltage going into the board

 

[Jay]

Tested with a few magsafe cables. Shield to ground, center conductor to +, set V and A... nothing. Different Mac, nothing. Guess I was sent a faulty PSU.

 

[smiba]

Check if if even outputs current.

Set the PSU to 1V, 1A and short the leads. It works it should go into current limit

I've had 3 broken PSUs before I had one that worked, just pay some good money for one. All the <$100 ones are likely DOA in my experience

 

[dukefawks]

Why don't you measure?

 

[Jay]

Smiba, this is the power supply Louis links to under his videos. I try to get tools and parts through his links/store so some cash flows his way as well through the affiliate program. It’s about $150. And if it’s good enough for a pro it should be good rnough for me I figured.

Duke, because sometimes the easiest solution is the one I think of last

Will test shortly. As always thanks for the replies.

 

[Jay]

I set it to 1V and 1A, output is 20mV and dropping.

 

[jadao]

Jay, I think you need to use - and + on your power supply not gnd and +
- to the shield magsafe cord
+ to the center (white) conductor
Good luck

 

[dukefawks]

How are you expecting the machine to work if you connect 1V to a magsafe connector? Or is this connected directly to PPBUS now?

 

[Jay]

Nono, I used the 1V for test with meter. With the magsafe I use the Volts and Amps appropriate for that model Mac.

 

[smiba]

I set it to 1V and 1A, output is 20mV and dropping.

Yeah so it's dead

Did the same as all those models that arrived DOA with me. Slowly it builds up a charge but the >500kOhm from the multimeter is already enough to slowly drain this.
Just to be sure, can you see if it works by connecting it to Positive and Negative instead of ground? I think ground is more like the earth wire which you definitely shoudnt just connect things to, I've always used the Positive and Negative on my supply

I use the Velleman labps3005N with great success but it's a European company so I think it's hard to get in the US

 

[Jay]

Will test with - instead of GND tomorrow. jadao mentioned the same, was just waiting for confirmation that was the way to go

EDIT: Yup, using - instead of GND everything works as it should. Thanks jadao and smiba for pointing that one out.