Physitemp Instruments BFS - Manual (Page 5)

3.0 THE POWER SUPPLY
3.1 The power supplies for all stages are physically alike. They plug into any standard three wire outlet
or, with an adaptor, into older two wire outlets. The power supplies for the BFS-3 or 5 are capable of provid-
ing an output 5V DC at a maximum of 10 amps. The BFS-30 power supply provides 12V DC at a maximum
of 10 amps.
Please note: The BFS-30 and BFS-3/5 supplies are not interchangeable and under no
circumstances should a BFS-3 or 5 stage be used with the BFS-30 power supply.
3.2 BFS units have only two controls:
(1) The CURRENT control. This increases cooling when roated clockwise. When
turned fully counter-clockwise, it clicks off.
(2) The FREEZE/THAW switch. As long as this spring-loaded switch is held down, the
stage top plate will heat instead of cool. The fast warmup facilitates removal of frozen
tissue from the stage.
4.0 SET-UP: MOUNTING THE STAGE
4.1 If the user specified the make and model number of his/her microtome when ordering the freezing
stage, it should have been supplied with the correct mounting hardware already in place. Available hardware
includes a 3/4” vise block and two 1 1/2” pillars of diameter 15/32” and 3/8”. Special mountings can be
made to order.
4.2
The stage has a 10/32” tapped hole in its underside. Into this hole can be screwed either of the two
pillars or the square block, which is supplied with a stainless steel screw. If not already fitted, the correct pil-
lar or vise block should be screwed into the underside of the stage and tightened. The stage should then be
firmly clamped in the microtome and adjusted so that connecting leads and tubing are clear of the knife and
other moving parts.
5.0 SET-UP: WATER COOLING
This section gives instruction for set-up if the equipment is to be used with tap water.
If a Pump and Tank Unit is to be used to circulate the cooling water, see Appendix 1.
5.1 Thermoelectric modules are solid-state heat pumps: As one side gets lower in temperature, there is
a corresponding rise in temperature on the other side. The head pumped through the module must be
removed. This can be done either by air or water cooling. The former requires copper radiation fins, for
which there is little space in most microtomes. In BFS stages, water cooling is used. PVC tubing carries a
trickle of water from the lab faucet to the module and leads it away to waste disposal.
5.2
Connected to the stage are an electrical lead and two PVC tubes which terminate in male self-seal-
ing connectors. A pair of 5’ water tubes with mating female connectors is also provided. Connect the 5’
tubes to the tubes on the stage. Attach one tube to the laboratory water supply, while the other goes to a con-
venient sink or drain. The direction of the water flow through the module is not important. The water supply
should be adjusted until it flows steadily from the output tube without spurting.
5.3
If the water supply is accidentally reduced or turned off while the equipment is operating, the
stage will tend to heat up. However, the electronic safety control will sense the rise in temperature and close
down the equipment before damage can occur. When this closedown occurs, the meter on the power supply
will indicate zero current flow; the red pilot lamp will continue to glow.
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