VIDEO HEAD EVALUATION

In the service manuals for the Beta units is usually found an evaluation section that outlines a procedure for checking the condition of the video heads. In the lower right corner of the illustration above is a chart that accompanies the method outlined in the manuals. Before we discuss the test procedure look briefly at the meter shown in the three photos, and specifically at the one in the top left photo. Notice the slide switch on the meter marked "mode" and also the "BATT" area on the pointer scale, it is just below the little red bar. I point these out because this instrument is battery operated and prior to any testing we are going to check the condition of the batteries. If the pointer goes into the BATT section on the scale when the mode switch is in the 'BATT" position, then the batteries are good and then it can accurately test the heads. Next we calibrate the meter by setting the slide switch to "CAL" and rotate the calibration knob (seen in the upper left photo in the lower right corner) to place the pointer directly over the "CAL" line on the scale. With these steps completed we can now put the switch in the "MEAS" (measure) position and we are ready to test. As you can see from the photos the leads of the heads are unsoldered from the round printed board and the test leads of the meter are placed on each lead. Polarity is not a concern even though the leads are colored. Consulting the manual we find it directs us to set the "RANGE" switch (in most cases) to the "B" range. The position of the pointer will now tell us the condition of the heads. Photos illustrate are the following: top left weak heads, top right good heads, photo lower left new heads. Disregard the the A' and B' heads (the apostrophe is called sharp) because they are the second half of the dual azimuth head configuration found in the higher end special effects Beta VCRs. For simplicity we are not going to discuss them other than to say they are tested in a similar manner. Referencing the chart we are comparing the areas marked A, B and C as they relate to the photos. Top left is testing as a two, which means they are getting worn. Top right a six, which is excellent and the new heads in the bottom right, also a six which is good. Both heads of the set are measured. The dual azimuth heads mentioned earlier get two measurements each. As you see from the chart the arrow showing the range for good heads doesn't extend all the way over to six, the chart is showing what they consider to be the "OK" or acceptable range. New and very good heads routinely measure in the higher numbers. Because the method used to measure the heads is based on the resistance offered by the small windings of wire around the core the procedure is not perfect. Heads can be physically damaged and still check good. So visual inspection is also required, as well as a performance check to evaluate the playback capabilities of the heads. The flying erase head(s) aren't mentioned in the manuals for testing but I have found from experimentation that they measure similar to the A and B heads. The heads measured in the top left photo would be replaced during refurbishing even though they could be considered useable. Click on the picture to see how to tell if video heads are bad by the visual or playback method. This page is taken from the section on refurbishing a Beta VCR. If you wish to go to the beginning of that section click on "Beta Refurbishing" in the navigator bar. To close this window and go back to the main page click here.