[ltp] Alternative power supply for A31

Richard Neill linux-thinkpad@linux-thinkpad.org
Fri, 20 Oct 2006 00:37:31 +0100

Mendel Cooper wrote:
> The power supply for my A31 TP is starting to get a little flaky (probably
> bad contact on ground shield litz). So, I thought I'd try using a 770 TP
> brick. Same connector and same 16-volt output voltage. Only difference
> is that it has a lower power rating 3.36 amps, as opposed to 4.5 for
> the original supply. That's 53.75 watts, instead of 72 watts. Seems
> to me that even with 20 watts less, the A31 should still be within
> the safety margin, especially if I don't have the battery installed,
> so battery charging will not pull extra power from the AC supply.
> When the machine is running from battery, it pulls something like
> 22 watts.  Even when you consider that the display is dimmed and the
> CPU running slower under battery power, I would think that with full
> display brightness and full CPU speed the machine should still consume
> less than 40 watts. Plenty of safety margin on a 53+ watt supply.
> Yeah, I could buy a standard 72-watt supply on eBay for about $20,
> including shipping. And yeah, some eBay sellers warn against using a
> 54-watt supply because of possible damage to the computer, but I think
> they're exaggerating in order to sell their stuff.
> Anyhow, I've been running this A31 on the 54-watt supply for a few hours
> now, and with no problems. Any thoughts or experiences?

I think you're fine. But without the battery, you lose any sort of UPS. 
Also, when the machine is under full load, the current can be higher. 
What about USB-powered peripherals? (Can draw 2.5W per port). When 
running the optical drive?  I'd be surprised if you can do any serious 
harm (except premature PSU wear and tear), but do keep an eye on the 
temperature of your PSU, especially if you run the laptop flat-out on a 
hot day.