Thermo Electrophoresis Power Supply 250-90 User Manual

Instruction Manual

250-90 Electrophoresis Power Supply

WARNING

Please read these instructions carefully

before using this power supply.

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AVERTISSEMENT

Veuillez, avant tout emploi du générateur,

lire attentivement ce manuel d´utilisation.

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© 2003 Thermo Electron Corporation. All rights reserved. Thermo Electron Corporation, and Analyze, Detect,
Measure, Control are trademarks of Thermo Electron Corporation. Windows is a registered trademark of
Microsoft Corporation.

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164-3000-00 Rev. F

250-90 POWER SUPPLY

NOTES

250-90 POWER SUPPLY

SAFETY NOTICES

NOTICES DE SÉCURITÉ

WA R NING: This notice alerts you to a potentially dangerous situation.
AVERTISSEMENT:

Cette notice attire votre attention sur des dangers
potentiels.

CAUTION: This notice means serious damage may occur to your

power supply or chamber.

PRECAUTION: Cette notice attire votre attention sur des dangers

sérieux pour votre générateur ou votre chambre
d´électrophorèse.

WARNING

This power supply has been designed to be used as a source of DC power for electro­phoresis. It is capable of generating lethal currents. Use the same precautions as with any
electrical device. Do not operate without the cover in place. Do not connect the
output to earth ground. Do not operate in a damp, humid, environment where
condensing moisture may short out internal electrical components. Do not operate
with connecting cables which have exposed wires. Do not pull the leads out of the 4mm
output connectors while the unit is in operation. Follow all appropriate safety
measures outlined by the chamber manufacturer.

AVERTISSEMENT

Ce générateur a été concu pour être utilisé comme source de courant (DC) pour l´élec­trophorèse, et il est capable de générer un courant mortel. Prenez les mêmes précautions
que pour tout autre appareil électrique. N´utilisez pas l´appareil sans que le couvercle de la
chambre soit placé. Ne raccordez pas les sorties à la terre. N´utilisez pas
l´appareil dans des environnements humides, où la condensation pourrait causer des
dommages aux composants électriques internes. Ne mettez pas l´appareil en route avec
des câbles ou partie de câble dénudé. Ne retirez pas les câbles des sorties de 4mm pendant
que l´appareil est en fonctionnement. Prendre toutes les précautions recommandé par le
fabriquant de la chambre d´électrophorèse.

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NOTE:

This notice gives useful advice or suggestions to raise

the performance or reliability of your power supply.

1

TABLE OF CONTENTS

Specifications ..............................................................................................2

Warranty.....................................................................................................2

Intended Uses and Set-Up...............................................................................3

Operation of the Power Supply .........................................................................4

Using the Timer in the Count-Up or Count-Down Mode ..........................................6

Messages ...................................................................................................7

Appendix A. Setting Safe Operating Limits..........................................................7

Appendix B. Relationships Between Volts, Milliamps, Watts

and Chamber Resistance ...............................................................8

Appendix C. Running Multiple Chambers...........................................................9

Appendix D. Utilizing Automatic Crossover .......................................................10

Fuse Replacement .......................................................................................10

Service.....................................................................................................11

NOTES

250-90 POWER SUPPLY250-90 POWER SUPPLY

250-90 POWER SUPPLY

11

SERVICE

WARNING: This notice alerts you to a potentially dangerous situation.
AVERTISSEMENT:

Cette notice attire votre attention sur des dangers
potentiels.

This power supply is not equipped with any user serviceable parts except for the fuse.
Contact Thermo Electron or your local distributor for technical assistance if problems arise.

The telephone number is [phone], or [phone].

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250-90 POWER SUPPLY

2

SPECIFICATIONS

Type Output: Constant Voltage or Constant Milliamps with

automatic crossover

Maximum Voltage: 250 Volts
Maximum Current: 500 Milliamps
Maximum Power: 125 Watts
Regulation:

<

1%

Accuracy:

+

1.5 % full scale for each display

Number of Output
Terminals: Four sets of recessed 4mm output connectors

Safety Interlock: Load sensing shut-down-on disconnect. Key actuation

necessary to begin voltage generation. In the event of shutdown
due to power interruption, automatic restart is provided.

Timer: 0.00 to 24 hrs 00 min.
Input Power: 110 Volts or 240 Volts AC, 50/60 Hertz, 250 Watts
Ambient Operating

Temperature Range: 0°C - 30°C (non-condensing atmosphere)
Dimensions: 7.5” (D) x 8.75” (W) x 5.5” (H)

19cm x 22cm x 14cm

Weight: (net) 11 lbs 5 kg

Weight: (shipping) 15 lbs 6.8 kg

WARRANTY

This laboratory equipment was produced by Thermo Electron with the highest practi­cal standards of materials, workmanship, and design. The design and manufacture of
parts have been conceived with one purpose — to produce a unit which will give sat­isfactory service.

Thermo Electron guarantees this unit to be free from defects in materials or workman­ship under normal use or service for four years from date of shipment.
If, during this time, this unit proves defective in materials or workmanship, the
Company will repair or replace it free of charge if returned to us prepaid. This
guarantee does not cover damage in transit, damage caused by carelessness,
misuse or neglect, or unsatisfactory performance as a result of conditions beyond our
control or consequential losses as a result of our product.

164-3000-00 Rev.F ©01/04 Printed in USA

3

INTENDED USES AND SET UP

This power supply is intended to be used with electrophoretic devices designed to operate
at or below 250 volts and 500 milliamps. Four sets of output connectors operate in parallel
to provide a constant voltage (10 - 250V) or constant current (10 - 500mA); the maximum
power output is 125 watts.

Make sure that the unit is set up in a location where it is protected from physical damage,
moisture, corrosive agents and extreme temperatures. The unit should be readily accessible
for safe operation.

Use the power cord to connect the unit to the AC Mains carrying the appropriate specified
voltage (V

) in accordance with the rating label located at the rear of the unit. Make sure

that the mains receptacle has the proper 3-wire (grounded or earthed) connections.

WARNING

Do not pull the leads out of the 4mm output connectors while the power supply is in opera­tion!

AVERTISSEMENT

Ne retirez pas les cables des sorties de 4mm pendant que l’appareil est en fonctionement!

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Appendix D. Utilizing Automatic Crossover

Certain electrophoretic techniques require the careful adjustment of operating limits and the
utilization of the automatic crossover feature of this power supply. Automatic crossover
involves a transition from one mode of operation (constant current, for example) to another
mode of operation such as constant voltage.

Semi-dry electroblotting exemplifies the utility of this feature. Semi-dry transfer chambers
contain two closely spaced parallel electrode plates. A“sandwich” consisting of buffer-sat­urated filter paper sheets on the outside and a gel and a charged transfer membrane on the
inside, is assembled and placed between the electrode plates. Typical protocols suggest
that the transfer should be carried out at a constant current. As the transfer process pro­gresses, the buffer in the two filter paper layers heats up and begins to break down. This
breakdown leads to an increase in the overall resistance between the two plates. In the con­stant current mode, the increase in resistance leads to a voltage increase. Left unchecked,
the increasing voltage can eventually lead to arcing which would damage the electrode
plates, the gel and the transfer membrane.

To eliminate the arcing problem, the voltage should be set at an operating limit which is
below the threshold needed for the arc. As the voltage increases, it will eventually reach the
predetermined operating limit. At this point, the power supply will automatically cross over
from the constant current mode to the constant voltage mode of operation. As the transfer is
completed, the current will gradually diminish.

FUSE REPLACEMENT

This power supply is equipped with two identical fuses. These can be either 115V, 5A, 20
mm time delay fuses, or 240V, 3.15A, 20 mm time delay fuses. Disconnect the power cord
from the power supply before checking or exchanging the fuses. A fuseholder module is
located above the power cord receptacle at the rear of the power supply. The cap of the
fuseholder has two clips (left and right) that have to be depressed with your fingernails so
that the cap with the fuses can be pulled out. If the fuse is burned out, it has to be replaced.
Insert the new fuse into the cap and push this assembly back into the fuseholder module.

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9

Appendix C. Running Multiple Chambers

This power supply is equipped with four sets of 4mm output connectors which are con­nected in parallel. The significance of this fact can be explained by studying the following
statements.

1. The voltage is applied equally to all branch paths in a parallel circuit.

2. The current flow in the branch paths of a parallel circuit is determined by the
resistance of the individual paths.

3. The sum of the currents entering the branch paths of a parallel circuit is equal
to the sum of the currents leaving the branch paths of a parallel circuit.

A practical example of this is described as follows:
The power supply is connected to two identical horizontal submarine electrophoresis

chambers (cells A and B). The power supply output is adjusted to 100 volts, at constant
voltage, and the current display indicates 60 milliamps. By applying the three rules for par­allel circuits we can determine the following information.

1. The voltage applied to both Cell “A” and Cell “B” is 100 volts. (Rule 1)

2. The sum of the currents flowing through Cell “A” and Cell “B” is equal to
60 milliamps. (Rule 3)

Switch off the power supply and momentarily disconnect Cell “B”. Switch the power supply
back on and note how the output current reading drops to 35 milliamps. From this, the fol­lowing information can be derived.

1. The current flow through Cell “B” is equal to 60 milliamps minus 35 milliamps
i.e. a net value of 25 milliamps. (Rule 3)

2. The reason Cell “A” and Cell “B” have different current readings is due to the
difference in resistance between Cells “A” and “B”. (Rule 2)

WARNING

Do not pull the leads out of the 4mm output connectors while the power supply is in opera­tion!

AVERTISSEMENT

Ne retirez pas les cables des sorties de 4mm pendant que l’appareil est en fonctionement!
Always make sure that the DC output is off and that both of the leads are disconnected from

the 4mm output connectors on the front of the power supply before you remove the gels
from the electrophoresis chambers. This is particularly important when several chambers
are connected to the power supply at the same time since the “No Load Detection Safety
Feature” of the power supply does not shut the voltage output off when one of the gels is
still connected.

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OPERATION OF THE POWER SUPPLY

Figure 1. The Front Panel Layout.

1. AC Mains Power Switch

2. Adjustment Knob

3. Timer On, V at Limit and mA at Limit LEDs

4. DC On/Off Key

5. DC On LED

6. Display Key

OPERATION OUTLINE

Step 1. Fill the electrophoresis chamber(s) with buffer and insert the leads into the
recessed 4mm output connectors (12) on the front of the power supply (bottom right).
Make sure that the red leads are connected to the red anodes (+) and the black leads to the
black cathodes (-).

Step 2. Switch the AC Mains Power Switch (1) to the On position (1 = On; 0 = Off) At this
point the Set Display LED (7) and the V Mode Selection LED (9) will be illuminated. The
DC On LED (5) will be off.

Step 3. Use the Select Mode Key (11) to select the first operating limit to be displayed
and adjusted. Each time the Select Mode Key is depressed the power supply will advance
to the next operating limit. As the display advances, the Mode Selection LED’s (9) will
change to indicate the limit currently selected.

17. Set Display LED

18. Digital Volts/Milliamps/Time Display

19. V, mA and Timer Mode Selection LEDs

10. Actual Display LED

11. Select Mode Key

12. Four Sets of 4mm Output Connectors

1

2

3

4

5

6

7

8

9

10

11

12

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5

Step 4. Using the Adjustment Knob (2), adjust the first operating limit to the desired value
as shown on the Digital Volts/Milliamps/Time Display (8). Operating limits can range
between 10 and 250V, 10 and 500mA and 1 minute (0.01) and 24 hours (24.0); (.00 =
Timer Off). Several seconds after the desired setting has been entered, the power supply
will automatically revert to the Actual Display Mode and the Actual Display LED (10) will be
illuminated.

Step 5. Return to Step 3 to select the second operating limit. Once selected, the user may
rotate the adjustment knob or depress the Display Key (6) to switch to the Set Mode. Once
in the Set Mode, the second operating limit can be set. Use the same procedure to set the
last operating limit.

Step 6. Press the DC On/Off Key (4), and make sure that the red DC On LED (5) is
illuminated. Note that the Actual Display LED (10) is now illuminated. Verify that the appro­priate values for the selected operating limits are displayed on the Digital
Volts/Milliamps/Time Display (8).

Step 7. The Timer On LED (3) will tell you whether your count-down Timer has been acti­vated, and the V at Limit and mA at Limit LEDs (3) will indicate whether you are operating
at constant voltage (V) or at constant current (mA), respectively. You can also check the
limits which have been set and the actual operating conditions, at any time, by pressing the
Display (6) and Select Mode (11) keys.

NOTE:

Rotating the Adjustment Knob (2), at any time, will cause
the power supply to automatically switch into the Set Display Mode.
When this happens the Set Display LED will be illuminated and the
operating limits may be changed. Approximately 5 seconds after the
Adjustment Knob stops rotating the power supply will revert to the
actual mode and the Actual Display LED will be illuminated.

NOTE:

The Adjustment Knob (2) can be turned clockwise and
counterclockwise past zero. For example, the voltage may be set at at
0 when the power supply is switched on, but the user may want to set
it to 245V. If the Adjustment Knob is turned counterclockwise the volt­age can be quickly set to 245V.

NOTE:

Some users prefer to set up the chamber, switch the
power supply’s output on, and adjust the operating limits before the
samples are actually loaded. If you choose to do this follow these five
steps.

(i) Confirm that the chamber and the power supply are functioning

properly,

(ii) Determine what the safe operating limits are,

(iii) Switch the power supply’s output off using the DC On/Off Key,

NOTE CONTINUED ON NEXT PAGE

8

Set = 125V, 55mA
Actual = 125V, 45mA

In the procedure listed above we first determined the actual milliamps output for operation
at 125 volts and then chose operating limits that were at a slightly higher level than those
indicated for milliamps. This approach ensures that the maximum output from the power
supply will never exceed the normal operating conditions (volts or milliamps) by more than
10%.

Appendix B. Relationships Between Volts, Milliamps, Watts

and Chamber Resistance

There are three fundamental concepts which form the basis for understanding the relation­ship between volts, milliamps and chamber resistance. When combined with the power for­mula they also define watts.

1. A movement of free electrons from atom to atom forms an electric current which
is measured in milliamps (mA) or amps (A).

2. Electrostatic lines of force between two different charges produce a pressure that
can move electrons (measured in volts).

3. All substances oppose the movement of electrons to some extent and are said to
have resistance (measured in ohms).

These three factors are always present in any operating electric circuit. It is possible to
incorporate them into one inclusive statement:

Ohm’s Law

The value of the current that will flow in any circuit will be directly proportional to the value
of the voltage applied and inversely proportional to the value of the resistance.

or

amps = volts / resistance

combined with

The power formula:

volts x amps = watts

(where 1 amp = 1000mA)

Together, these two formulas define all aspects of the relationship between volts, milliamps,
watts and chamber resistance.

NOTE:

When the power supply is used in constant current mode,
select an operating time for volts which is greater than the actual value
by 10% or 25 volts, whichever is greater.

250-90 POWER SUPPLY250-90 POWER SUPPLY

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The count-down Timer can only be used for runs with a duration of 24 hours or less. A
series of short audible pulses indicates that the run timed by the count-down Timer has
ended and that the power supply’s DC output is switched off.

MESSAGES

The depression of any key on the front panel will be accompanied by a short audible tone.
This message will confirm that the key has actually been depressed.

A series of short audible pulses indicates that a run timed with the count-down Timer
has terminated.

The flashing E01 error message appears when the power supply detects an open connec­tion to the chamber. This message will occur at the beginning of the run if the leads are not
properly connected, or during the run if one of the leads is inadvertently disconnected, or if
the buffer has leaked and there is a lack of conductivity in the chamber. Depress the DC
On/Off Key or switch the power supply off and on with the AC Mains Power switch to clear
the E01 error message. Check the connections and the buffer level before pressing the DC
On/Off Key to proceed with the run.

Appendix A. Setting Safe Operating Limits.

Most chambers are made of acrylic plastic which may warp at high temperatures (above
55 °C). For this reason it is especially important to determine the normal operating
conditions for each application and to confirm they do not exceed the safe operating limits
of the chamber being used.

The following procedure illustrates how normal operating conditions can be determined
and how this information can be used to choose safe operating limits for an agarose gel
run in a submarine chamber at a constant voltage of 125 volts.

1. Adjust the operating limits to 125V, 500mA, Timer at 0.00.

2. Start the run by pressing the DC On/Off Key, and note the mA value when the
voltage has reached 125V and the V at Limit LED is illuminated.

3. Adjust the mA setting so that it exceeds the actual value by 10% or by 10
milliamps, whichever is greater. Thus the Set and Actual values may look like this.

NOTE:

Some electrophoretic techniques can store energy in the
chamber over a period of time. This energy, which manifests itself as
a low voltage, may inhibit the normal function of the load sensing
interlock. When a run is restarted, an E01 error message may appear
and the power supply may not start. To overcome this effect, press
and hold the DC On/Off Key again until the power supply’s voltage
begins to rise.

6

USING THE TIMER IN THE COUNT-UP

OR COUNT-DOWN MODE

This power supply is equipped with a dual function Timer. In the passive, or count-up
mode, the Timer will accrue elapsed time when the DC On LED is illuminated. In the active,
or count-down mode, the Timer will keep track of the elapsed time, and terminate the high
voltage DC output and sound an alarm at the end of the set time interval.

Time is shown in hours and minutes during the first 9 hours and 59 minutes (9.59), and in
hours and 10 minute intervals between 10 and 24 hours (10.0 - 24.0).

Count-Up Mode

To utilize the Timer in the passive, count-up mode, the time interval must be set to .00
before the DC output is activated. In the count-up mode, the Timer will be reset to zero
(.00) if the DC output is switched off by pressing the DC On/Off Key or by switching the AC
Mains Power Switch off; a power failure will also reset the count-up Timer to .00 .

The count-up Timer can accrue time for up to 24 hours. When more than 24 hours have
elapsed, the DC On LED and the Digital Volts/Milliamps/Time Display will flash.

Count-Down Mode

To use the Timer in the active, or count-down mode, a time interval must be set before the
DC output is activated. Once set, the Timer will count down whenever the DC On LED is
illuminated. Note that both the DC On LED and the Timer On LED will be illuminated, indi­cating the timer is functioning in the count-down mode. In the count-down mode there is a
pause function. The Timer will pause during the run if the DC output is switched off
with the DC On/Off Key, or if there is a power failure. The Timer resumes when the DC
On/Off Key is switched on, or when power is restored. When the power supply is switched
off with the AC Mains Power Switch, the count-down timer will be reset.

NOTE CONTINUED:

(iv) Load the samples, and

(v) Switch the power supply on using the DC On/Off Key and

readjust the operating limits if necessary.

The power supply will retain its settings in memory only if the DC out­put has actually been activated. Once in memory, the settings which
are being used for the run will be retained until they are changed by
the operator.

250-90 POWER SUPPLY250-90 POWER SUPPLY