Hi,

just asking: is the dell computer connected in any way to the same battery,
maybe for power supply?

my idea is, if you use the same battery as a power source maybe you are
creating a sort of a "ground loop" when you connect the rs-232 port.

Paolo from Italy

> -----Messaggio originale-----
> Bill Nicoll
> Inviato: domenica 27 agosto 2000 8.26
> Oggetto: [M]: Still blowing fuses - RS232 port related
>
>
> This evening I set up my scope for some viewing (first clear night in
> Southern Colorado in weeks), turned on the power switch on the scope and
> promptly blew the fuse behind the control panel.
>
> Briefly, my equipment is an LX200 running on a 12v. battery with the
> Meade 12-18 v. converter, and a Dell laptop running The Sky connected to
> the scope's RS232 port with a serial cable. I have used this setup
> numerous times with no problems.
>
> I unplugged the power cord from the scope, checked the voltage
> (18.25v.), replaced the fuse (2 amp. slow blow), turned on the scope and
> blew another fuse. This time I noticed that in the second before the
> fuse blew the current meter on the scope was maxed out, with all the
> bars lit up. I then replaced the fuse again, unplugged the RS232 cable
> (I don't no why I did this, just a hunch I guess), turned on the scope
> again and it worked perfectly, with the meter in the normal tracking
> range (3-4 bars lit). I then turned off the scope, plugged in the RS232
> cable, turned on the scope keeping my finger on the switch, noticed that
> the meter immediately went to full load, and switched off the scope
> before the fuse could blow. When I unplugged the RS232 cable once again,
> the scope functioned normally.
>
> I experimented with this for a while and learned that the current meter
> maxed out only when the cable was plugged into one of the computer's com
> ports. It didn't seem to matter if I left the cable plugged into the
> scope, as long as it wasn't plugged into the computer. Also it didn't
> matter if the computer was turned on or off, simply plugging the cable
> into the port was all it took to peg the meter. I tried 3 different
> cables and both com ports, always with the same results. I inspected the
> com ports for bent pins and found nothing that looked wrong.
>
> Does anyone have any ideas, also could this be related to the RS232 port
> problems discussed in the thread of the last several days?
>
> Bill Nicoll
> Pueblo, Colorado
>
>
>
>

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