Thinkpads Forum

Hi,
I have a minidock (type 2878) which has a power socket with 4 pins.
I have a 16v 120w PSU, but this has a single barrel type connector.

Does anyone know what the 4 pins are actually used for?
How are they configured (pin x = +16v etc etc)?
A wiring diagram would be great.

I have searched the IBM website and although it has lots of info and manuals it barely mentions the 4 pin power input and I cannot find any wiring diagrams.

Thanks a lot,
Mike

The 2878 Mini-dock uses a unique 120W power brick (FRU P/N: 02K7092) in which, with the orientation key of the connector at the top, the leftmost pins are negative and the two rightmost pins are positive.

ftp://ftp.software.ibm.com/pc/pccbbs/op ... 2p1837.pdf

James

JHEM wrote:The 2878 Mini-dock uses a unique 120W power brick

Not quite unique, it was used for Thinkpads (G series?) as well.

Cheers,

Bill B.

bill bolton wrote:Not quite unique, it was used for Thinkpads (G series?) as well.

Thanks Bill, I had forgotten about the G series use.

James

Thanks guys,

So if I understand it right ..... and because I am allergic to big flashes and bangs I think I had better double check!

If I look at the back of the Minidock at the power connector socket:
(a) the Left two pins = Negative.
(b) the Right two pins = Positive.

Any idea why 4 pins are used and are they all +- 16v DC?

Thanks,
Mike

mikemmb wrote:Any idea why 4 pins are used

My guess is that it has something to do with the original application as a G series Thinkpad power supply rather than anything in particular to do with the Mini-Dock per se.

IBM clearly just reused a ThinkPad family power supply they already had in production with the sort of power rating needed for the purpose, rather than creating yet another unique power supply.

The Mini-dock needs a beefier power supply than the port replicator (which gets by with a standard T4x power supply) as it has to be able to run everything on the attached Thinkpad, plus the additional circuitry in the Mini-dock (particularly including powering the 4 additional USB 2 ports).

Cheers,

Bill B.

Hi,
My current thoughts are to just parallel up the 2x positive and the 2x negative pins ................ but something is stopping my hands moving towards it without knowing what I am doing.

The kit is out of warranty, but still a shame to blow it up!

Does anyone out there have a wiring diagram or know for sure how these four pins are used?

Thanks,
Mike

Hi,
At last I got round to looking at where the 4off power cables go to on my minidock but I am stuck!!

To get a look at the cables from the power socket I need to get the minidock apart and cannot figure it out?

I have removed 5 screws and expected the case to open up ....... but it does not show any sign of splitting apart.

Anyone know how to open up the case on a minidock??

Thanks,
Mike.

mikemmb wrote:At last I got round to looking at where the 4off power cables go to on my minidock

A simple resistance test, using a low ohms scale, with a Multimeter on the pins in the socket on the MiniDock should show you whether the two + pins and two - pins are connected to each other, without needing to open up the case.

Cheers,

Bill B.

Thanks Bill,
I will try that tonight ......... just hope I don't read xxOhms!
regards
Mike

After getting sidetracked for a day or two I got round to doing a resistance check on the Minidock Socket to see if the Left Two Pins (and the Right Two Pins) are directly connected:

- The Left Two Pins show a resistance of 0.2R between them.
- The Right Two Pins also show 0.2R.

This seems a relatively high value and suggests to me they are not simply connected together in parallel. On the strength of that I was not brave enough to connect them together and power them up.

Someone out there in the big wide world must know how/what/why they are used ..... even better a wiring diagram of a Minidock would be great.

Thanks in anticipation,
Mike.

mikemmb wrote:- The Left Two Pins show a resistance of 0.2R between them.
- The Right Two Pins also show 0.2R.

If by 0.2R you mean 0.2 ohms, that's close enough to a short circuit that you are possibly reading the resistance of the multimeter test leads, or similar.

Cheers,

Bill B.

Hi Bill,
Thanks for your reply, my R was shorthand for Ohms .... getting lazy in my old age!

Touching the probes together gives a reading which hovers between 0.01 and 0.02 which is much lower than the 0.2 between pins.

So my guess is that it is unlikely that the pins are directly soldered together in pairs at the back of the socket, but I suppose could be linked by a more roundabout (higher resistive) route.

I still cannot figure out why a pair of pins would be used though, it makes no sense and pushes up production costs. Surely the pin rating would not be exceeded by just using one pair?

Oh what wonders a Wiring Diagram would reveal!

Regards,
Mike.

PS. I don't think it will be much longer before I give in to the temptations of the big hammer and chisel.