Thinkpads Forum

Here's a question I've been scratching my head over for a little while.

I received two power adapters for my T60, both of them being genuine Lenovo units. Both are marked as being 65W adapters... not so good, as I have discrete graphics and really would need a 90W to run anything intensive.

However, one of the two adapters is quite different... it is physically larger than the other one, has a green LED power indicator, and is recognized by my machine to be a 90W power adapter. So... is this a strange messup with my machine, or is this simply the case of wrong labellng?

Listing the FRUs from the two adapters would probably help. The only Thinkpad power supplies that I've seen which have a green LED are the AC/DC combo supplies, but those are the older 16V adapters. Not sure if any of the newer 20V ones have them or not; I only have a single 90W brick to go by.

Hm... strange. The one with the LED is definitely a 20V; it's currently plugged into my T60.

The FRUs are:

LED brick, recognized as 90W, labeled as 65W: 92P1157

Non-LED, smaller, labeled and recognized as 65W: 92P1214

Edit: The 'LED Brick' is marked with "2006.06" which I'm assuming is a date... my T60 has a June 2006 date on the bottom, so it is likely this is its original power adapter. I think this is a Canadian machine as I purchased it from Canada, but I'm not 100% sure on that... could be a power adapter specific to that market.

Well, as you suspected, the 92P1157 is supposed to be a 20V 65W unit; it's listed as being made by Lite-on. Don't know why your system thinks it's a 90W but what may be possible is that the center pin on the DC plug is being used to communicate/identify itself. Unplug the supply from the AC outlet and try cleaning the pin with a Q-tip.

ref: http://www-307.ibm.com/pc/support/site. ... 62730.html
ref: http://www.kawakami-ca.com/images/20v_dc_plug.jpg

Hmm. I went ahead and cleaned it out... and it's still being recognized as a 90W adapter.

Another discrepancy I'm seeing in the first link is that I'm seeing that IBM lists this as being a three-pin adapter(I'm assuming they mean a grounded plug)... this is only a two-pin adapter(without a ground pin). I'm starting to think this just might be one screwball 90W adapter.

Yes, a three-pin would be the "Mickey Mouse" type of AC cord (two lobes on top, one below in the center looks like the outline of Mr. Mouse's head ). The information I've seen about the 92P1157 is that it was replaced by the 92P1153; a Delta unit (also supposed to be a three-pin adapter).

edit: You could try connecting a 4.5 ohm resistor across the DC plug and see if the adapter can still deliver 20V

Note: This is a mildly amusing (at least to me) way of testing the supply but it requires at least a 4.5 ohm 100W resistor to be done safely. Not the kind of component one would have laying around on the workbench.

LegendaryKA8 wrote:Hm... strange. The one with the LED is definitely a 20V; it's currently plugged into my T60.

The FRUs are:

LED brick, recognized as 90W, labeled as 65W: 92P1157

Edit: The 'LED Brick' is marked with "2006.06" which I'm assuming is a date... my T60 has a June 2006 date on the bottom, so it is likely this is its original power adapter. I think this is a Canadian machine as I purchased it from Canada, but I'm not 100% sure on that... could be a power adapter specific to that market.

According to this, it's an overseas adapter.

FWIW I have several 65W and 90W 20V adapters that came with ThinkPads or that were purchased separately from Lenovo Canada. None have LEDs.

rkawakami wrote:Note: This is a mildly amusing (at least to me) way of testing the supply but it requires at least a 4.5 ohm 100W resistor to be done safely. Not the kind of component one would have laying around on the workbench.

You might be surprised. If you have 3 100W incandescent bulbs try wiring them in parallel and then check with an ohmmeter. My 100W bulbs measure ~13Ω each

I'm not sure abought the light bulb idea. They are meant for A/C operation and I believe the resistance changes as they get hot. It takes more energy to light than maintain.

richk wrote:They are meant for A/C operation

Unlike CFLs, there's nothing in the design of an incandescent bulb that requires AC. They work just fine on DC.

the resistance changes as they get hot. It takes more energy to light than maintain.

Yes and yes, however at 20V that's not going to be a problem for at least a few seconds, i.e. long enough to establish that the AC adapter can pump out 90W.

My suggestion was meant to be partly tongue-in-cheek since anyone who needs to test AC adapters under load would likely get a rheostat. The advantage of a rheostat is it would allow them to vary the load to meet the specs of each adapter they were testing.

I have two different size 90W adaptes for my T61s - the larger of the two came off the port replicator and has the LED. Maybe that's the difference?