Continuing in the tradition of this site in covering obsolete technology, this is the long overdue post about the VHS and the VCR. There will be a few more to be made as time goes by … good things all take time!
Introduction, with added Nostalgia
Video Home System, more commonly known as VHS, was the dominant home video recording format through the 70’s, 80’s, 90’s and 00’s. It won out over the visually technically superior Betamax format and offered longer run-times. VHS offered users an affordable way to time-shift television programming, and a way of preserving home video memories. It was also used to copy (dub) recordings for back-up purposes. VHS cassettes became inexpensive and was commonly available in various lengths (commonly E-120, E-150, E-180, E-240 and E-300 in Australia).
Recordings on VHS were easily transferred between machines, and later in its life, Hi-Fi audio recording on 6-head VCRs increased audio quality markedly. Recordings were made by a spinning drum in a helical scan technique to increase tape-to-head speed and bandwidth. VHS tapes were easily re-used and re-recorded, and LP modes were available to double the recording time at expense of quality. The picture quality was always below broadcast quality, but was generally acceptable to most people (as we didn’t have any better).
Towards the end of the 2000’s, VHS decks became scarce and many retailers stopped selling them. Production of VHS decks declined in quality significantly in the last decade, mostly focusing on offering low-cost, rather than high durability and quality. As a result, flimsy light mechanisms and non-modular designs became common, and spare parts almost impossible to obtain. Repair was not a design factor. The same thing could be said of some of the later cassettes as well.
It was the earliest video format I became a user of. I did manage to salvage a few Umatic cassettes at one stage, but disposed of them. Just another thing I regretted doing. I never had access to a Umatic deck though.
I remember it fondly as a child, being mesmerized by the spinning drum, and the constantly turning reels. It was also fascinating to watch the blinking VFD (later, LEDs) on the front of the VCR and listen to the clicks and whirrs of the VCR changing between operating modes. I mastered the use of the VCR at an early age, and could actually program the clock and timer recording. It wasn’t that hard – and yet, many people had their VCRs blinking 12:00!
We had a variety of Sharp decks – a four-head mid-drive, and a two-headed “regular” one, and a four-head multisystem. We also had a single Philips deck, and these saw me through from childhood right up till the end of primary school. These ended up dying due to belt failures, and other mechanical ailments. After that, we finally acquired our first 6-head decks, a Samsung (which I’m using now), a Teac and a Tevion (both of which were probably given away). We also got a NEC two-head (which I have as a back-up) with a TV purchase, and a Panasonic 6-head Super Drive (which was salvaged).
Unfortunately, as we were “late” to the 6-head party, the majority of the recordings we have were all made on 4-head or 2-head decks, hence the audio is pretty poor for frequency response and there was no stereo either.
It wasn’t long before I performed maintenance on VHSes and VCRs as well – head cleaning was a common operation, as well as splicing back together broken tapes that had their leaders snapped. It was through disassembly that I was able to understand how the cassettes worked, but I also appreciated subtle differences in each brand of cassette.
In fact, it was while I was cleaning out old cassettes that I came across this note I wrote for myself, reminding me that a given cassette was an E-150, not an E-180. Of course, it’s obvious now when you look at the supply-reel or the markings above the write-protect tab.
With the introduction of digital TV, our use of the VCR declined dramatically. Seeing that the whole country has now moved over to digital TV, it is likely that many people are moving away from VCRs and VHSes and instead towards DVD recorders and PVRs instead for the higher quality recording ability and greater convenience of not needing to rewind a cassette or clean a head! As a result, I had a pile of VHSes which I needed to clear, which might become interesting to others over time. Different VHS artwork, different TV commercials. It all brings back memories.
It is because of all of this, that I decided that the VHS deserves a permanent home on this blog, affectionately dubbed (no pun intended) the VHS corner. In this area, you will find a variety of posts covering the VHS system itself, various VHS cassettes in my collection and content I’ve uncovered on VHS.
The VHS Cassette
This, is a VHS cassette. It’s actually a repaired cassette, not that it matters. It looks pretty anonymous, but I can tell already just from looking at it, that it’s likely a Teac S-HGX. How do I know? Well, you can see the reel cut-outs and shell “shape” – there are subtle differences between most reputable manufacturers.
Anyway, let me introduce you to all that is the VHS cassette. This is the top of the cassette, looking through the reel windows. The left reel is the supply reel, the right reel is the take-up reel. The cassette is inserted in the direction of the arrow, and can only be used this side up. The centre section is reserved for a label. The top area is part of a hinged flap which protects the top surface of the tape during transport.
The underside of the cassette is a collection of holes. The two large circular cutouts allow for the driving tangs to engage with the teeth in each reel. There is a reel lock which prevents the reels from turning freely and loosening tape during transport which is disabled once an object penetrates the hole in the middle lower of the picture. The middle-upper hole allows for a end-of-tape sense light to enter the cassette. Likewise the top cutouts allow for the capstan and pinch roller (left) and two guides to enter the cassette and pull the tape out into the machine. The whole assembly is typically secured together with five screws, although there are a few uncommon exceptions (e.g. TDKs in general).
The spine of the VHS reveals another labelling area along the length of the cassette and a write-protect-tab area on the left-bottom area. In the above case, the tab has been broken off, engaging the write protection feature. To re-use the cassette, this has to be covered over with self-adhesive tape. Above this write-protection tab, often the manufacturer codes for the cassette are printed, which identify its length (and possibly, manufacturer, batch code).
Propping open the top flap, we can see the tape path of the cassette. In this case, the tape is going from right to left. The clear plastic tape is the leader, and is fitted at the ends of the cassette, allowing the deck to sense the end-of-tape condition and stop the motion of the tape before slamming into the end and possibly snapping the tape. This could happen on some decks where the sensors have failed, or the light source has failed. Repairing a cassette by clipping raw tape to the spindle will result in no clear leader, thus the VCR will slam into that end upon rewind – so preserve the leader where possible, but don’t make splices within the tape (as a bad splice can destroy a head – I’ve made two splices mid-tape and luckily, both caused no damage).
The tape runs across metal rotating rollers at each end, although newer cheaper cassettes might omit them altogether. It enters the tape shell, where there is a nylon guide roller for the take-up reel, and a “cleaning pad” and metal post for the supply reel.
Here, you can see the button that releases the cover flap on the left image. This is the right side of the cassette, and you can see the end of tape sense hole. In the right image, you can see the hole on the left side of the cassette for the end of tape sense hole for that end. It works because there’s a light path from the centre hole to these holes when the leader tape is wound past the level of the hole.
This is demonstrated by the LED torch in the image above.
Removing the five screws, and turning the cassette back over the correct way allows the top to be removed. Don’t do this upside down, or you’ll get a shower of parts.
Clearly visible is the reel locking mechanism consisting of two springs, and three plastic parts. There is the supply and take-up reel, along with the guide rollers and wipers. There’s also the push button to release the flap.
The internal top shell contains the spring-loaded self-closing tape cover lid. There is also a springy piece of metal which pushes down on both reels to seat them onto the mechanism.
Here, you can see the cut-out in the centre hole which allows for the light to pass through the leader to the sensing hole on the side of the cassette to sense the end of tape condition.
This is the edge view of one of the reels. Here you can see the clear leader, and the plastic clip used to secure it to the hub. There is a clear top-plastic which “keeps” the tape in place on the reel, and the white plastic rear. The circumference of the rear plastic is covered with slots which enable the reel lock mechanism to work correctly.
The reel lock mechanism is pretty self-explanatory by now. The spring loaded plastic part in white slots into a slot in the outer rim of the reel back, thus holding the reel in place. The tip of this plastic part is specially shaped to allow one way movement, such that the reels can tighten the tension on the tape, but not release it without being deactivated.
The reel lock is deactivated when an object goes into the reel lock hole, which turns the black plastic piece in the foreground, applying pressure to both spring loaded parts such that the tips retract away from the reels, thus freeing them for motion.
Here is the take-up roller mechanism – a rotating polished metal cylinder and a nylon roller.
The supply reel mechanism is a little different with a black piece of plastic touching a metal roller. The tape passes inbetween and it acts a bit as a cleaner/tensioner. There is also one hollow metal cylinder roller.
Now you know pretty much what all the parts in a VHS cassette are!
Inside the VCR
This is my currently used VCR, a Samsung SV-650B. This is considered a fairly modern VHS deck, built in the cheap way, with no modules, and as little metal as possible. It’s quite light, but it’s been fairly reliable. The quality is not remarkably good, but it’s the best I have at this moment. There’s a lot of things to talk about when it comes to quality conversion, but that is best discussed in another posting.
A clue to its modern status, aside from the date (25th January 2003), is the Super Speed Rewind function. Rewinding cassettes used to take a long time, until Jet-Rewind mechanisms became common, enabled by microprocessor control and detection of differences in rotation rate between the two reels. It can be considered a little harsh on some cassettes, but time is precious! The fact that it’s got 6-heads, Hi-Fi stereo is another clue.
Lets take a look at the mechanics inside the VCR.
There’s really not much in this compared to the first VCRs I used. I struggled to lift those early ones, and they were warm and jam packed full of stuff. This one’s mostly empty space. The bottom PCB houses almost everything that runs the VCR, the left side is the power supply, the right side can is the tuner, and the right side chips all do the video/audio. Underneath the transport itself is the rest of the logic that runs the VCR.
The transport itself is the centre sections – the reel drives are in black. The eject motor is on the right side corner. The two guides extracting the tape can be seen in their “home” position, ready to slide up the slots and wrap the tape around the drum, erase and control/linear audio head. The black rubber pinch roller and capstan make up the rest.
It looks pretty simple! Lets take a look at each component in turn.
The component in black is the linear erase head. The tape runs by this head first, which erases the tape in a vertical band across the tape. This is necessary when re-recording over existing footage. There is also a hole in the metal plate where the end of tape sensor is.
The left guide can just be seen in the foreground, which has the vertical roller keeping the tape tensioned across the erase head, and the angled pin which wraps the tape at an angle across the drum.
This is the drum assembly. There is the fixed section below, separated by the “thicker” gap. The top section spins at about 1800rpm, and houses six heads in this model in four “cutouts” – one of which is facing us in the image above. These heads protrude very slightly from the surface of the drum and scan the tape. The drum itself is driven by a direct drive motor above, which is very similar to what floppy drives use.
The second guide roller is seen, and the reverse happens in this roller – the slanted tape is pulled back to vertical to pass the control and linear audio head.
There is the control and linear audio head with the blue connector above. This provides the servo timing signals from the tape edge which help control tape speed and tracking, and the monaural “low-fi” audio. The tape then passes the guide pin and has its speed controlled further by the capstan and pinch roller before being wound back onto the take-up reel.
This is the infrared LED which protrudes up from the base into the cassette for the end of tape detection. This appears to be a special LED with one emitter but a lens on both sides so that infrared emanates both toward the left and right.
The tape path is clearly visible with the cassette loaded.
Here you can see how the tape wraps around the drum. The grooves in the spinning section of the drum help to control the air bearing that keeps the tape flying just above it.
The Heads Up Close
While I have my camera out, lets take this opportunity to get a close look at the heads.
This appears to be an audio head because it appears to be a single head. Remember, you cannot see the gap visually as it is so small, but you can see the head chip itself, and the coils which sense and record.
This is a pair of video heads, by the looks of it. Notice how it looks like the above structure, just narrower, with two side by side? This is your A and B’ head which allows for better still frame and forward/reverse video, and often one optimized for SP and the other LP. There is a gap between the two heads … you can see some oxide collecting. The outer edge is clearly “worn” away by friction with the tape over time. The other pair of video heads looks like this …
Again, the wear is apparent, as is the oxide. This is why you have to clean your heads … the oxide buildup can clog the head gap or alter its magnetic sensitivity. I might as well give them a clean now that I’ve gotten this far …
… nicely done!
I couldn’t resist taking a shot of the direct drive motor windings – it’s pretty colourful.
There is also the tracking and control head – it was hard to get a close-up, but it appears it’s very similar to those used in audio cassettes.
The Deck in Motion
Here are two videos I shot – the first shows you the different operating modes (I didn’t choose fast-rewind).
The other shows you the Super Speed Rewind in action – it’s quite harsh to the tape but it’s pretty darn fast!
I very much affectionately remember the VHS and the VCR. In fact, I’m dealing with them right now – quite possibly – for the last time in my life. Rather unexpectedly, as a technology, it lived a long life and was a consumer revolution, and it bought me many hours of entertainment as well as a few things to do (rewind tapes, clean heads, etc).
It’s a bit sad that kids of the new generation won’t understand when we say the clock on the VCR is blinking 12:00, nor would they understand the difficulty in programming a VCR (especially pre-OSD and pre-Gcode days). Nowadays, things are so easy that people don’t read the manual. I actually enjoyed reading the manual to the VCRs – that might have been just one of the reasons I ended up as a tech-person.
There’s actually a lot of technical complexity behind the VHS system, much of it I still don’t understand precisely. Luckily, there are quite a few good resources online that still cover these aspects – the next (wordy) post will look at some of the technical aspects.