Re: LF: Noise R75 - rs232 from smpsu -

[Andy Talbot <andy.g4jnt@googlemail.com>]

Yes, I've played with running laptops including Dells from all sorts of power supplies.  The nominal voltage can go a goodly 10 - 20% either way before it flags an error - and they seem to detect over voltage and take evasive action, although couldn't guarantee all do.

 

BUT there's a big snag with Dells.  If youv'e got one with the three way coaxial DC connector (it has a very thin centre pin) - the PSU contains a DS2502  one-wire EEPROM..   The Laptop interrogates the PSU to find out if its satisfactory and if the EEPROM isn't present, the laptop will use the external power, but refuse to charge the battery.    On a 12V input mobile PSU I had to butcher a surplus Dell black brick to get the EEPROM and incorporate it into the connector for the new PSU.

 

Those EEPROMS are supposed to be easy enough to read, so when I need one again, will read the contents and stick them into a fresh chip.

 

Andy
www.g4jnt.com

On 23 July 2010 21:47, Laurence KL7UK <hellozerohellozero@hotmail.com> wrote:

 
Anyone done any common mode noise mitigation from the RS232 port of the R75 Rx> - the noise coming up from the SMPSU/processor from the old Dell puter - cable is double screened - choking off using J (75) type has seen little improvement - this is my last hurdle to unimpeded remote rx on 137 - any pointers appreciated - everythings bonded and Ive tried the on/off earth tricks at various locations -
 
Anyone had any success of powering a Dell D series from a non standard non switched PSU? (the noise goes away when the DC from the Black Dell brick is removed but it may also be partially screen/processor noise...)
 
with thanks
 
Laurence Kl7UK

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