Lake Shore Model 218 Temperature Monitor User’s Manual
7-8
Service
7.11 EPROM AND NOVRAM REPLACEMENT
The operating software for the Model 218 is contained on one Erasable Programmable Read Only
Memory (EPROM) Integrated Circuit (IC). The reference designator for the EPROM is U17. See
Figure 7-7. The EPROM has a sticker on top labeled with “M218.HEX” and the date. The reference
designator for the Non-Volatile Random Access Memory (NOVRAM) IC is U24. Use the procedure
below to replace either the EPROM or the NOVRAM.
NOTE:
The factory may provide the CalCurves™
to users in U24 (NOVRAM).
CAUTION: The EPROM and NOVRAM are Electrostatic Discharge Sensitive (ESDS) devices.
Wear shock-proof wrist straps (resistor limited to <5 mA) to prevent injury to service
personnel and to avoid inducing an Electrostatic Discharge (ESD) into the device.
1. Follow the top of enclosure REMOVAL procedure in Paragraph 7.10.
2. Locate EPROM U17 (M218.HEX) or NOVRAM (U24) on the main circuit board. Note orientation of
existing IC. See Figure 7-7.
3. Use IC puller to remove existing EPROM/NOVRAM from socket.
4. Noting orientation of new EPROM/NOVRAM, use an IC insertion tool to place new device into
socket.
5. Follow the top of enclosure INSTALLATION procedure in Paragraph 7.10.
7.12 ERROR MESSAGES
Model 218 error messages during normal operation:
Disabled
Input is turned off.
No Curve
Input has no curve.
S. Over
Input is at/over full-scale.
S. Under
Input is at/under negative full-scale.
T. Over
Temperature
conversion
went
off the high end of the curve.
T. Under
Temperature
conversion
went
off the low end of the curve.
Error 1
Defective
NOVRAM.
Error 2
Invalid NOVRAM — Press and hold Escape for approximately 20 seconds to initialize
NOVRAM. Refer to Paragraph 4.13.