Hickok 800 Calibração - Página 5

Procurar online ou descarregar pdf Calibração para Equipamento de teste Hickok 800. Hickok 800 6 páginas. Tube testers

If the ENGLISH control is not balanced it will have to be adjusted. While proper balance is vital to the accuracy of

measurement, calibration is done by adjustment of the control under Control Alignment described below in the MUTUAL

CONDUCTANCE CALIBRATION section.

Control Cleaning:

If the ENGLISH control is dirty or intermittent it is best to remove it from the tester to clean both sections. If you

are not experienced in taking apart controls do not use this as a learning opportunity. It is fairly easy to ruin one and there

are no replacements other than salvage from a junk tester. Set the control to the center of rotation before working on it. Do

not rotate the shaft more than a short distance while the halves are separated. On older controls that do not completely

separate, if you rotate past the stop you can drop the front wiper into the slot between the ends of the element and it will be

difficult to get it back out.

The back cover is press fit onto the end of the back section shell and can be removed by prying it off. On the older

controls you cannot completely separate the front section from the back. To separate them enough for cleaning, remove the

retaining ring around the shaft where it enters the front section then melt the solder spot and gently pull the shell apart only

far enough to keep the solder from holding the two halves together when it cools and no farther. Once the shell sections are

separated remove the solder from the surfaces. Gently separate the front section shell from the cover just enough to provide

an opening to infuse an appropriate cleaning solution. A couple of toothpicks placed in the gap will hold the halves

separated for cleaning. Never attempt to pull them farther apart as this will bend and destroy the front section wiper

components.

On newer controls the front section comes completely apart by removing the retaining ring from the shaft and

sliding the shaft out the back of the shell after it has been separated. The wiper and center tab can be removed and cleaned.

The back section cannot be disassembled as the front section but there is enough exposed to do a cleaning.

The main problem is not the wirewound element or the slider on the wiper but the sliding contact between the wiper

and the center lug of the control. Old dried out grease, dust and tarnish on the contacts that connect the center tab to the

wiper are the main problems. A good cleaning method is to immerse the control in an ultrasonic cleaner for a few minutes

using a detergent solution in water. Afterward, give it a good rinse with clean water and then a second rinse with a mild

water soluble solvent such as isopropyl alcohol to purge the water. Follow up with an air dry. After cleaning reassemble the

control but do not reapply the solder to the shell. Do a control alignment as described below in the Control Alignment

section under MUTUAL CONDUCTANCE CALIBRATION.

14. MUTUAL CONDUCTANCE CALIBRATION: The mutual conductance reading in this test is controlled by the setting

of the ENGLISH control and the accuracy of the meter. Check the meter accuracy as described above in ADJUSTMENT

CHART step 1. A bad or dirty ENGLISH control will cause the readings to be wrong. If necessary, cleaning the ENGLISH

control as described above in Control Cleaning should always be done before adjusting the mutual conductance calibration.

If the readings are incorrect follow the Control Alignment procedure below to adjust the control to the proper calibration.

A difference of one or two small divisions might be seen if you rotate the control and set it to the orange dot by

rotating it counterclockwise instead of clockwise. This is because the ENGLISH control is not a precision device nor was it

ever intended to be. It has a certain amount of inaccuracy in the resistance and instability in the mechanical motion. This is

about the best you can do with an instrument of this age and caliber.

Control Alignment:

Remove the tester from the case. Remove the ENGLISH control from the tester. Note the small spot of solder on

the side of the shell of the ENGLISH control. Remove the solder so that the shell of the back resistor section can rotate

with respect to the front section. Block the tester up on a level surface with the front panel facing up. The top edge of the

control panel should be facing you so that you can see the meter and push the buttons.

Temporarily connect the ENGLISH control to the tester with clip leads and place it in a convenient position such

that you can hold it and adjust it. Verify that the AC line adjustment is correct. Rotate the ENGLISH control fully

counterclockwise. Put the ENGLISH knob on the control and rotate the knob without rotating the shaft to align the zero

setting to some convenient landmark. Tighten the set screw on the knob and, using the landmark, rotate the control to the

orange dot near number 73. Connect the calibration test circuit and perform the mutual conductance reading test. Secure

switch P4 down and while holding the back section of the control stationary, rotate the shell of the front section until the