10-8
Reciprocal Shaking Water Baths
Thermo Scientific
Section 10
Troubleshooting
**** Problem F: Motor Does Not Shake Tray (continued) ****
7. Check Power Supply Board #3166924.
a.
If Step 6 has checked out fine, then possibly the power circuit for the
motor has failed. Locate the diode CR11 on the POWER SUPPLY
board and place a DC voltmeter across it with the positive lead on the
cathode (band side) and the negative lead on the anode. The listed
voltages appear across the diode for different speeds. Select a couple of
these speeds and verify the voltages.
*** Problem G: Motor Speed Erratic or Fully on ***
1. Check Optical Disc.
a. The optical disc should be free of foreign material. If not, clean disc.
b. The disc should be parallel to the bottom of the bath and centered in the
optical sensor. If not, loosen the 2 set screws on eccentric and reposition
the disc.
c. The disc should be smooth and flat. If the disc is bent or warped then
replace the disc.
d. While the motor is operating, the disc should NOT come in contact with
the optical sensor at any time.
2. Check Optical transmitter.
a. Connect negative lead of a DC voltmeter to TP1-COM on CPU board.
b. With the bath "ON" and motor "OFF" or "ON", use the positive lead of
the voltmeter to measure the voltage at J303-Pin 1 of the CPU board.
The correct reading should be approximately 1.2 volts DC. If the
reading deviates considerably from this, replace the optical sensor.
SPEED
SELECTED
VOLTAGE ACROSS CR11 -
VOLTS DC
30
20
50
30
70
40
90
50
110
60
130
70
150
8
