T22 wont start from battery

[roncoinc]

it has a very good battery,will last a long time and takes a full charge... machine is new to me so no history..
starts fine off power supply,unplug it and runs fine off battery...
will not fire up off battery tho,absoloutely nothing ! plug it in,hit switch,as soon as lite goes on unplug it and away it goes..any suggestions ??

[rkawakami]

From that description I would say you have a defective power-up control circuit. There are a couple of chips from MAXIM (the semiconductor company, not the magazine ) that are on the T22 motherboard I have which exhibits the "blink of death" syndrome. My guess would be that one of them is not detecting the battery voltage upon power up and therefore does not initialize the rest of the power circuit. Once you have "fooled" these circuits into working properly by using the AC adapter, then you can run off the battery by itself.

[roncoinc]

interesting,,thank you....hhmmmm....now i'm thinking...a small battery with a plug to pwr supply to jump start it.keep it in the laptop case,only need it for a second to fool it..how about that ??

[rkawakami]

That's an interesting idea! You could easily get a coaxial power plug that fits the DC input jack and as long as you have it wired properly (center positive), the proper voltage (16V) and enough current to fool the power circuits into thinking you have an AC adapter... Now you just have to find a small enough battery that outputs the 16V needed. It might be possible to use a voltage lower than 16V but I would think that the circuits are smart enough to balk at anything below a certain threshold.

if you do try this, be sure to come back and let us know how that works (or not!).

[roncoinc]

just tried it on a power supply and 14vdc will do it..tried 5 cmos batts but not enuf current,will try 2 9v batts and see..

[rkawakami]

I wouldn't think that the 9V batts will be any good. IIRC, you can only get about 100-150mA out of them (NiCad or NiMh)... Don't know if alkalines are better. Can you monitor/measure the current being drawn with your 14V power supply?

edit: Just realized that 9V NiCad or NiMh batteries are actually less than 9V; somewhere around 7.2V I think... And the alkalines should be better based upon the length of time that they run my smoke detectors over the rechargeables. Probably about a 3 or 4:1 advantage.

[roncoinc]

yup,,,two 9v batts did it...plug em in hit button and pull the plug and away it goes ! making it neat is up to the imagination..

[roncoinc]

thanks ray,,used alkaline batts...the power supply measures in amps so i dont know how much it needs to start,,could use my dvm i suppose to see if anybody needed that info but the availability of batts to do this is limited so that fact may be moot.
now i wonder if there is something on the mobo i could jump to not make this neccessary.. ??

[rkawakami]

Did some poking around the net to find 9v battery specifications. Turned up an article on Wikipedia:

http://en.wikipedia.org/wiki/PP3_battery

9V alkalines are supposed to be rated around 500+ mA so you could probably start up the laptop many times before you deplete them. Nice solution!

As to something you could do to the motherboard... I'd look real closely around the Maxim chips. Look for Maxim MAX1631, MAX1632 or MAX1715 parts. It's possible that one of those chips or a capacitor associated with them, has lifted from the board.

[roncoinc]

Hello ray....i opted for the easy way out......instead of taking it apart to the mobo to look for something i probly couldnt fix anyway i went the battery route....two 9volt batts..soldered a wire from + to - ,,,then with a proper size dc plug soldered to the other + and - terminals...with correct polarity..hi quality elactrical tape wrapped tightly and neatly finished the project...it actualy looks pretty fair...
$4 worth of batteries and 15 min time it is just another accesory in the laptop bag..i showed the wife how to use it...open laptop,plug it in,,hit power button,light comes on,,unplug it,,put it away and puter boots just fine..
i thot this t22 @900mhz for $100 was a good deal..the onboard sound not working was solved by a $10 usb sound card,,the not starting from battery was a $4 fix..the frustration ,,PRICELESS !!..
anyway,,if these solutions can help anybody else keep the old stinkpad going good enuf....tnx for help and sugestions.....

[rkawakami]

Excellent solution! Hopefully the 18V will be tolerated well by the power supply circuits. With the amount of current being drawn by the battery pack when you press the power button (I'm assuming around 250-500ma), the voltage may be sagging low enough toward 16V. Then again, it may not be drawing all that much current if the battery is taking over immediately.

If you would like to insure that the battery pack is closer to the 16V that the AC adapter provides then you could either use a zener diode and current limiting resistor across the battery pack or a couple of diodes in series with one of the battery leads. Figure a 0.6v drop for each diode so you would need three diodes capable of handling about an amp of forward current (just to be conservative).

ref:
http://en.wikipedia.org/wiki/Zener_diode

[roncoinc]

No problem with input voltage there i dont think..from what i have seen at the input goes directly into a volt reg circuit...voltage to a regulator can vary widely,most 12vdc IC regulators will handle up to 36volts and regulate down from there..the voltage to start a regulator circuit must be high enuf to supply a referance voltage inside the IC plus voltage over the target level to regulate.the rest of the voltage is basically waste.
to much current in the battery is not an issue..
most of my dc regulation work has been with the LM 723 IC's and the old reliable LM317 series.....so as for whats in a laptop mobo i could be WAY off on this..
if i had a mobo to play with tho i could find out !