Martin - at the risk of being off topic from WSJT yes, Lenovo has a way of, ahem, "detecting" if a "genuine" AC adapter is plugged in, specifically a single resistor wired in parallel in the end of the adapter that plugs into the laptop.
Informational only, totally warranty-voiding link below. I would never do this to any one of my beloved fleet of 3 ThinkPads! But nonetheless the truth must be known. http://marc.merlins.org/perso/blog/cat/linux/post_2016-02-29_Hacking-a-thinkpad-slim-tip-adapter-to-output-more-than-90W-_required-to-charge-a-Thinkpad-P70_.html My current (pardon the pun) workaround is to not use a Thinkpad out in the field :-( Instead I have an Asus E-series ultraportable (<1 kg!) that has less "smart" power circuitry and happily takes a charge from a 12v to 19v DC/DC step up converter I bought on A Well Known E-Commerce Site. 73 de KB3ZUV -- Adam Schaible kb3...@schibes.com On Sat, Mar 16, 2019, at 19:00, Martin wrote: > I have a few of these in the shack for 19/20 V monitors and they seem okay > QRM-wise: > > https://www.ebay.com/itm/Lind-AC-Adapter-12V-Car-Power-Supply-Dell-90W-Laptop-HP-100-Mobile-Printer-/292957179784?hash=item44359bcf88 > > > I have a Thinkpad W540 and tried using one of the mobile 19V supplies - the > same voltage as the Lenovo factory power supply. When I booted I got a new > screen I'd never seen before. Lenovo was telling me to go out and buy a > genuine Lenovo power supply. I haven't looked further but I guess they are > using some signal riding on the 19 V to do this. > > 73 Martin W6MRR > > On Sat, Mar 16, 2019 at 3:39 PM Jim Brown <k...@audiosystemsgroup.com> wrote: >> On 3/16/2019 12:23 PM, Gary Hinson wrote: >> > You could check laptops and their power supplies in a friendly laptop shop >> > (when they are not too busy!), using a portable AM radio. >> >> Naw -- virtually place that sells or repairs stuff, or where humans >> live, is almost certain to be so full of noise that noise from one >> device is unlikely stand out. >> >> >> > Alternatively, you could simply banish switchmode supplies of all types >> ... >> > so either get/build a conventional PSU or find a laptop that will work >> from >> > the shack 13.8V supply. Many seem to be rated for 18V or more >> >> Yes, that's been true for nearly a decade. >> but I suspect >> > they might work at 13.8V although their batteries may not charge (don't >> > quote me on that: you'd need to check for yourself). >> >> The last ones I owned that fall into this category were from the >> Thinkpad T41-T42-T43-T44 series. And they do work that way. Beginning >> with the T60 models, introduced at least 10 years ago, they went to 20V >> power supplies and don't run on 13.8V. >> >> > >> > Hinson tip: look out for cardboard boxes of PSUs in charity shops. Either >> > pick out the bulky/heavy ones, or make an offer for the whole box. Check >> > them for safety before use. Supplies rated for wide-range inputs (e.g. >> > 110-250V without a selector switch) are generally switchmodes. The flying >> > leads and special connectors might be worth keeping, even if the PSUs >> > themselves are junk. Unregulated supplies typically produce several volts >> > above their rating off-load and only vaguely approximate the rated voltage >> > at the rated current ... so avoid powering valuable electronics directly >> > from them. Any PSUs that get hot are clearly suspect. >> >> This is good advice, which I've freely given for years. :) Another >> detail about voltage regulation -- the vast majority of linear wall >> warts and line lumps are transformer-rectifier-capacitor filter >> supplies, so open circuit voltage will rise to nearly the peak value of >> the transformer secondary with no load, and drop close to the label >> voltage at the label current. >> >> I break all the DC cables for these things and add PowerPole connectors, >> and use an inline meter with Power Poles to monitor voltage and current >> when matching a wart to a load. In my experience, you're pretty safe >> matching voltage and current ratings of the supply to the voltage and >> current spec of the device (usually marked on the SMPS that comes with it). >> >> 73, Jim K9YC >> >> >> _______________________________________________ >> wsjt-devel mailing list >> wsjt-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/wsjt-devel > > _______________________________________________ > wsjt-devel mailing list > wsjt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/wsjt-devel >
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