Table of Contents
Advertisement
Thermo Scientific
When the bath starts experiencing temperature problem and/or variations, due to
known controller malfunctioning, these two components become prime suspects.
The reason being that they are under higher operating stress than other
components.
If the bath starts experiencing temperature problems such as no heat, or
"creeping" upward heat, then follow the troubleshooting instructions below.
These instructions require the use of a voltmeter being able to measure DC and
AC voltages (preferably digital) and an ohmmeter.
Warning The following troubleshooting instructions require that power be On.
Only qualified service personnel should perform these procedures.
Open the control cover and familiarize yourself with the POWER SUPPLY
assembly #33176677. Locate the triac (Q2), the opto-isolator (U1), the resistor
(R4), and the test point #2 (TP2-COM). The first measurements will be DC
voltage measurements. A DC scale of at least 10 volts should be selected.
PROBLEMS & SOLUTIONS
*********** Problem A: No Heat
1. Verify that the setpoint temperature is greater than actual water temperature.
2. Verify that the HIGH TEMP light is "OFF". If the light is "ON", turn the
HIGH LIMIT CONTROL fully clockwise.
3. Check temperature probe voltage reference. These measurements are on the
CPU board #3176678.
a. Place the negative lead of a DC voltmeter on TP1-COM test point.
Measure the voltage at U7-pin 2. It should be approximately 14 volts
DC. Then measure the voltage at U7-Pin 6. It should be approximately
5 volts DC. If the 14 volts is present but not the 5 volts, the CPU board
must be replaced.
4. Check temperature probe.
a. Measure the bath water temperature and make note of it. Make sure it
will not change drastically during this check.
b. With a DC voltmeter, measure the supply of the temperature sensor at
J302 pins 1 & 3. It should be approximately 5 volts. If it is, then
continue on to Step 4c. If not, see Step 3a.
Troubleshooting Section 10
▲
**************
Reciprocal Shaking Water Baths
10-3
Advertisement
Table of Contents
