Welch Allyn 12500 Manuel de service télécharger pdf (Page 213)

Appendix

Inspections/Tests for Repaired 767 Transformers

Main Unit and Third Handle

IMPORTANT: When any primary component is replaced, perform the leakage current

test and the dielectric breakdown test as per the following specifications.

When checking the main unit, use Welch Allyn Tester T-13251 for leakage and dielectric strength

tests. Measure output by using standard components / bench equipment set up as described

below for the main unit.

1. Apply the calibrated *resistance to the handle stud to simulate a controlled lamp resistance.

This may be supplied by using a fixed resistor and a variable resistor (pot) in parallel.

* Calibrating the 767 Test Load

The 767 functional test consists of measuring the voltage delivered by the 767 lamp driving

circuitry when a calibrated resistance or load is put in the circuit instead of a lamp. The method

for building the calibrated load is as follows:

a) Connect a 5 ohm potentiometer or an equivalent combination to obtain the desired

nominal lead.

b) Connect a regulated 3.5 volt supply (ac or dc) to the load through an amp meter and

adjust the potentiometer until the current delivered is 750 mA. (This will effectively be a

circuit with a 4.66 ohm nominal load).

c) This resistor combination including the current meter is the calibrated load which should

be applied when measuring the 767 output. Alternately T#13251 can be used.

2. Adjust input line voltage for domestic 767: 116 VAC+9 / - 3 VAC RMS.

Adjust input line voltage for international 767: 230 VAC+/- 10 VAC RMS.

3. When handle is connected to test load circuit above, output (Rheostat Full On) of the 767

should be 3.5 VDC +/- .5 VDC. (Use a true RMS meter set on DC scale).

4. Measure third handle outlet output at the slot jacks on the right end of the 767 main unit.

When measured with a Beckman (or equivalent meter) set on the AC scale, this output

should be 7 VAC +/- 1 VAC with a nominal load of 9.33 ohms.

5. Measure leakage and hi-pot (dielectric strength) with tester T-12351. Follow

instructions for tester.

6. Perform functional check of handle rheostat. Look for smooth typical operation.

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Welch Allyn 12500 Manuel de service Page 213