http://thomsoneu.blogspot.com/2020/05/rebirthing-surface-pro-2.html
I therefore concluded that the problem was the adapter.
I figured just buy a spare. Ah not so easy. The JB Hifi fellow told me there were two types. A low power version used on the RT and a high power version used on the Pro. He he no high power versions and his computer showed neither did any other JB Hifi stores. A quick trip to Harvey Norman showed the same problem. Dr Google advised that the low power version can be used on the Pro Surface but will take longer to charge. Back to JB HiFi and bought a low power version.
For posterity I measured the voltages on the pins. Starting from the outside we have the - then +12.3V with the purpose of the centre unknown. The two +12.3V pins are connected together. Likewise the two GND pins. ie you can measure from either ground pin to either +12.3 pin and get the required voltage.
I believe the centre pin is for overcharge protection.
ReplyDeletethe center pin is used to energize the four power contacts with full current capability. The idea is, when disconnection occurs, the center pin will not receive a + voltage from the computer and the power supply will instantly drop the power level available to the socket in order to reduce the spark at the connector. You will notice the center pin requires full contact of the four power pins before the center pin makes contact. This slight pin height gives the power supply an advantage to reduce current supplied to the four power pins when the connector is disconnected. The same wait until all four power connectors are seated before applying the full current from the power supply to the computer; occurs when connecting the power supply connector to the computer. Got that concept? The power supply can provide +12.3 VDC at low current and this will not cause a damaging spark at the connector pins. Once the connector pins are seated and the center sense pin makes contact, then the power supply can ramp up the current necessary to charge the battery and operate the computer.
ReplyDeleteVoltage is like the height a water hose can spray and current is like the diameter of a water hose. The higher the water sprays, the higher the measured voltage. The larger the water hose diameter, the more current available.
Voltage can be measured with a volt meter and current with a current meter.
By-the-way electrons flow from the power supply via the negative terminals, loop around inside the computer and computer battery, then return to the power supply via the positive terminals.
Very informative, thank you!
ReplyDeleteI bought one of these power supplies from an op shop, wondered why the voltage collapsed when a load was applied. This post and comments has helped. Cutting the connector off and removing the wires insulation, there are four wires inside:
ReplyDeleteThick red wire is +12v.
Thin yellow wire connects to +12v to delver full power.
Thin blue wire connected to the centre pin shuts off the power when connected to +12v.
Opening the connecter revels what the yellow wire connects to.
The yellow wire connects through a resistor to an led and then to GND. While a diode connects between GND and the yellow wire.
When the yellow wire is connected the blue wire turns to +5v.
I can't work out how the surface connects the yellow wire to +12v.
Even though I haven't figured out fully how t works hopefully someone will found this useful. :)
This information definitely came in handy when repairing a relative's Surface charger where only the red wire was still connected. Saved me some trial and error, thanks!
DeleteHello , could you please make small drawing for the wires coolours and 5 pin connector .
Deletehttp://thomsoneu.blogspot.com/2020/05/rebirthing-surface-pro-2.html
Delete