Service Forum

[Subwon]

hey victor or bob. i ran itester pluged it to the serial port and both values are equal. but as soon as i ground it on the circuit board the values are diffrent to each other.

do you think i need to remake my interface?

[victor]

[Subwon]

i ground by mounting to a screw hole on the system board

heres a bit more info:

when i plug the serial plug in, on the itester values for 'sda in' and 'sda/scl out' are either both 1 or both 0. but when i connect to the epromm chip and then run itester the 'sda in' and 'sda/scl out' values are different 1 and 0 ect.

i know i shouldnt connect to chip with itester running but just tried grounding it on things, and i could ground off other object without the values changing but as soon as i ground it on the motherboard (mounting it on a screw hole) the values differ from each other.

[Subwon]

When choosing between parts for the interface do i use

Resistors:

1 watt 22k ohm Resistor or 0.6 watt 22k ohm resistor.

Zener Diodes:

1 watt 5.1 v Zener diode or 400 mW 5.1 Zener diode.

[victor]

You should use 2.2Kohm, I think that was the problem - wrong resistors.
Use 2.2K/0.15W - 0.25W
The wattage has no importance for this interface, is just a matter of size.
_________________
Victor Voinea
ALLservice HQ, Romania.

[Subwon]

Hey i remade the interface, turns out a zener diode exploded. now when i connect to the epromm and run r24rf08.exe it comes back with this error:

ERROR: Circuit not found or bus error!

can you help?

thanks