Lime Rev-1

These engineering change notes may apply to any 2B0 units.

There are no engineering differences between the lime (shown at left) and green coloured units.

The 2B0's PCB rev-number can be found on the solder side along the edge of the PCB under the 8 pin U8 chip.

RS232 fix for simultaneous Display and PC connection

Problem : Although there are two RJ45 connectors on the 2B0 unit, not all of the signals can be shared among like devices. Since the introduction of the LD02, it's possible for the 2B0 to be simultaneously connected to a display (LD02, LA1, etc.) and a PC (or other serial device) for logging. This may result in the loss of logging control by the PC (or the display). The problem is that the RS232 Tx pin's voltage levels from the PC and the display interfere with each other, even though they may not both be transmitting any data at the same time.

The fix is relatively straight forward and involves adding two diodes to the 2B0's PCB. You can get us to modify it for free (but freight costs may apply) or follow the details below.

The fix is shown, in diagram form, at right. Click on the image to enlarge. The two diodes are small signal items like the 1N4148, but higher spec diodes like the 1N400x series will do equally as long as they are physically small and easy to attach.

Note that the bands on the diode are connected at the common point (left side). the black heatshrink is simply to prevent the diode's leads from shorting against any components leads.

The schematic of the change is shown at left. The two added diodes are shown in the shaded blue area.

Optimised WB_lin +/- drive, R223 R233 change

Some units were shipped with R223 of 1 k (shown below) rather than 47 ohms as is now recommended. This is shown in the schematic at right where the original 1k resistor has been crossed out and replaced with 47R.

This is a minor irritation and should cause no problems in the field, but It's worth making the change if you're opening the case anyway. The 1 k may have the effect of limiting the possible range of WBlin when the WBlin- reference goes much below 0 Volts, but this will only occur if you connect WBlin to a very low impedance input.

Make sure you understand how J5 the WBlin +/- jumper works.