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Always On USB Connector

T430 and later, plus T530 and later series specific matters only
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Rockrz
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Always On USB Connector

#1 Post by Rockrz » Tue Aug 06, 2019 2:38 pm

I bought a power cord and they sent me one that has a USB plugin on the end.

The end of the USB plugin itself is yellow, so can this be used to plug in to the "Always On USB Connector" in the back of my T530 and it will run the laptop, and charge the battery?

Recently, my battery does not appear to be charging and the laptop will shut down even with my original power cord plugged in... and due to this I was thinking the power supply may be bad which is why I bought another one, and they sent me one that has a USB plugin on the end.

Just wanting to know if I can use this power supply they sent me or not
(I thought I was buying one like I had which was not USB on the end but apparently not)

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Re: Always On USB Connector

#2 Post by TPFanatic » Tue Aug 06, 2019 6:51 pm

It's not a USB connector, it's the newer (new being from 2014) rectangular power port used in **40 generation Lenovo ThinkPads. You would need a rectangle to barrel adapter to use this with your T530. It does not plug into the yellow USB port. The laptop cannot get charged through the yellow USB port.
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Re: Always On USB Connector

#3 Post by Rockrz » Tue Aug 06, 2019 7:10 pm

OK, thanks.

It's odd that Lenovo makes a power supply with a USB end on it if plugging it in to the USB port does not power the laptop.

I guess they are making these just for fun or something because I see them being sold in numerous places on the net.

I guess I'll toss it in the trash since it's useless...

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Re: Always On USB Connector

#4 Post by JPOESQ » Tue Aug 06, 2019 7:44 pm

Rockrz wrote:OK, thanks.

It's odd that Lenovo makes a power supply with a USB end on it if plugging it in to the USB port does not power the laptop.

I guess they are making these just for fun or something because I see them being sold in numerous places on the net.

I guess I'll toss it in the trash since it's useless...
Don’t toss it. Many of us have computers with that power connector and can use it.
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Re: Always On USB Connector

#5 Post by axur-delmeria » Tue Aug 06, 2019 11:56 pm

Rockrz wrote:
Tue Aug 06, 2019 7:10 pm
It's odd that Lenovo makes a power supply with a USB end on it if plugging it in to the USB port does not power the laptop.

I guess they are making these just for fun or something because I see them being sold in numerous places on the net.
As already mentioned, it's not a USB connector. It's the standard power connector for Thinkpads starting from the T440 generation. Basically, the round power jack on your T530 is the last of its kind.

The change was done because the round plug was too big, and Lenovo wanted to make thinner laptops.
I guess I'll toss it in the trash since it's useless...
There's an adapter like this that converts the new plug to the old, round one:

Image

But you need to buy one that's matched to your charger's output (65w, 90w, etc.)

Alternatively, if you know someone handy with electronics, you can have that person splice the old connector onto the new charger, provided that they have the same output (as I mentioned earlier). This is important because there's a resistor inside the power connector, which the Thinkpad uses to detect the charger's output current.

So if you splice the connector from a 90w charger into a 65w charger, the Thinkpad will incorrectly identify it as 90w and draw more current than the charger can supply. This will lead to an early death for the charger, and may also damage the laptop as well.
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Re: Always On USB Connector

#6 Post by RealBlackStuff » Wed Aug 07, 2019 12:37 am

I have one of these, which does not have a built-in resistor, it's straight-through, so use it with any charger.
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Re: Always On USB Connector

#7 Post by dr_st » Wed Aug 07, 2019 1:41 am

axur-delmeria wrote:
Tue Aug 06, 2019 11:56 pm
There's an adapter like this that converts the new plug to the old, round one:

But you need to buy one that's matched to your charger's output (65w, 90w, etc.)

Alternatively, if you know someone handy with electronics, you can have that person splice the old connector onto the new charger, provided that they have the same output (as I mentioned earlier). This is important because there's a resistor inside the power connector, which the Thinkpad uses to detect the charger's output current.
Interesting. How come the other-way adapter was never offered (as far as I know, even by Lenovo) in more than one kind?

Is it perhaps because of:
RealBlackStuff wrote:
Wed Aug 07, 2019 12:37 am
one of these, which does not have a built-in resistor, it's straight-through
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Re: Always On USB Connector

#8 Post by axur-delmeria » Wed Aug 07, 2019 1:58 am

But the resistance values for the round connector and rectangular one are different-- see https://thinkwiki.org/wiki/Power_Connector

Round plug:

Code: Select all

power	resistance
65 W	10 kΩ
90 W	not connected
135 W	0 Ω
170 W	1.5 kΩ
Rectangular plug (AKA slim tip):

Code: Select all

power 	resistance
36 W	7,3 kΩ
45 W	120 Ω
65 W	280 Ω
90 W	550 Ω
135 W	1 kΩ
170 W	1.9 kΩ
230 W	4.6 kΩ
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Re: Always On USB Connector

#9 Post by dr_st » Wed Aug 07, 2019 2:18 am

Interesting indeed. I have a few of these old-PSU-to-new-laptop converters; some genuine Lenovo, some third-party. I guess I should test them with different adapters and see what's reported. But I don't feel like installing the Lenovo Vantage bloatware on my laptops. :x
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Re: Always On USB Connector

#10 Post by RealBlackStuff » Wed Aug 07, 2019 2:46 am

None of those adapters should have any resistor, they are only adapters, NOT converters!
I had some of the first round-to-rectangle cable adapters with a resistor.
I just cut them open and replaced the resistor with a piece of wire.
Later versions (angled, without cable, as below) that I got had no resistor either.
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Re: Always On USB Connector

#11 Post by dr_st » Wed Aug 07, 2019 2:53 am

Right. So if they do not change the center pin resistance level, how does the laptop correctly detect the PSU type?

Looking at the tables axur-delmeria provided, I see that the values are all unique. One explanation is that Lenovo programmed all the new laptops to recognize the resistance level both of the old and the new adapters; this would explain why the "old adapter to new laptop" converters need not bother with it. However, old laptops obviously do not know how to detect the new adapters, so they should use "smart" adapters that adjust the resistance.

That's just a theory; we'd need some testing to verify / disprove.
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Re: Always On USB Connector

#12 Post by RealBlackStuff » Wed Aug 07, 2019 3:05 am

The chargers (or their DC-plugs) have the resistor built-in, the above adapters are just that, adapters [or shape-shifters if you like]. :wink:
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Re: Always On USB Connector

#13 Post by dr_st » Wed Aug 07, 2019 2:26 pm

Well, I couldn't resist, so I installed the Lenovo Vantage bloatware (temporarily) and ran some test on the Thinkpad 25.

With the genuine Lenovo adapter it correctly detected both the 65W and the 90W round barrel tip PSUs; with the no-name knockoff adapter, both chargers were detected as 90W.

Needless to say that the original rectangular plug chargers as well as the USB-C chargers are correctly detected with appropriate wattage.

I don't have any other chargers (>90W) here to try, so there are still no conclusive answers, however it suggest that (at least some of) the knock-offs are not as good as the genuine Lenovo tip converter; since they make any PSU look like 90W to the laptop, I would only safely use them with 90W PSUs.
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