The condition of a VCR's video heads is always a big concern. The best electronics in the world won't help if they can't get good information from (and to) the videotape. In the illustration above there are several examples of what you might see if the video heads are worn. These were made using a pattern generator that produces the recordable video image shown in section number 1. Going left to right from there you can see that the picture degrades as the heads begin to wear. Number 2 shows annoying specks that can start to show up, and number 3 it is getting worse, and in 4 they are almost gone. Number 5 is complete failure or damaged heads. If the tracking isn't on center it can produce similar results. So it has to be dead on for making an accurate determination. Dirty heads can also produce a bad picture. If using my Video Heads Cleaning Cassette will not clear the picture of specks, white lines, and streaks, then it could indicate new heads are needed. Seeing the picture noise is usually the first clue that something is going wrong. Another way to test the heads involves using the Sony SL-5151 video head checker. The procedure for using this instrument is explained in the service manuals. Click on the above illustration. As you can see from the three photo segments around the chart the leads going to the heads are unsoldered, and the checker test clips are attached to each lead. Polarity is not a concern even though the leads are colored. The service manual directs us to set the "RANGE" switch to the "B" range. (Is this for Beta?) Sony doesn't say, but all the Betas are tested in the B range. The position of the pointer tells the condition of the heads. Consult the chart taken from the manual in the lower right. It illustrates the different ranges, what to look for and what they mean. Photo sections indicate the following: top left, are weak heads, top right good heads, photo lower left new heads. The A' and B' heads are the second half of the dual azimuth heads (DA) found in the higher end Beta VCRs. These are for a clear picture in pause and step. Both heads halves are measured. Referencing the chart, we are comparing the ranges marked A, B, and C. On the top left, this head is testing a 2, which means it is worn and getting closer to replacement. The top right is a 6, which is excellent and the new heads in the bottom left also show a 6. The dual azimuth heads mentioned earlier get two measurements each (total of 4) and are slightly more complicated. What the measurement is showing is the resistance of the ring that makes up core of each head. The procedure is not fool proof. Heads can be physically damaged and still check good. Visual inspection is part of any head evaluation. The video heads in the top left would be replaced as part of my refurbishing procedure, even though they could be considered usable. Testing the flying erase head(s) isn't discussed in the service manual, but I have found from experimentation that they measure similarly to the A and B heads. Click the illustration, and here are three closeups of video heads as they wear throughout their life. Click on it again to see the video heads wear chart. As you can see, wear decelerates as the heads grind away and exert less friction is exerted on the tape. If you suspect that the video heads are nearing the end of their life there is another method you can use to check them for yourself. Here is how to do it. Record a short dark segment in the  speed using a L-250, L-370, or L-500 cassette. It must be done only using one of these lengths. They have a thick based film (tape) wound inside them. Rewind and examine the playback. Make note of the number of sparkles, streaks and lines that appear in the picture over a short time period. Make a second recording using a good L-830 cassette to compare. It has a thin-based tape inside it. Watch its playback and evaluate the two recordings. If the second one looks better than the first, then the heads could be wearing out. If both look equally bad then the heads are either dirty, damaged, or wearing out. Now, if you haven't already, iy would be a good time to try using my Video Heads Cleaning Cassette to clean up the picture. If after cleaning both recordings still look bad then the heads are either damaged, too dirty to get clean, or worn out. It is assumed in these tests that the cassettes are of good quality and capable of making clean, clear recordings, and that the tracking is on center. I offer a kit that includes the tools for the this head evaluation. Examine the "Video Heads and Tension Testing Cassettes" by click here.
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