Reliability and Usability
The cartridges have an audible pause due to the presence of a length of metallic foil, which a sensor detects and signals the end of the tape and acts as a splice for the loop. The foil passes across a pair of electrical contacts which are in the tape path. Contact of the foil closes an electrical circuit that engages a solenoid which mechanically shifts the tape head to the level of the next track.
Most players produced a mechanical click when switching programs, although early Lear players switched silently. Because of the expense of producing tape heads capable of reading eight tracks, most eight-track players have heads that read just two tracks. Switching from program to program is accomplished by moving the head itself. Since the alignment of the head to the tape is crucial to any tape system, and because eight-track systems were generally designed to be cheap, this configuration further degraded the sound of the eight-track tape.
The Stereo 8 system was fairly simple, mechanically, but presented difficulties in two primary areas:
- Capstan wear and buildup. As tape residue, dirt and lubricant built up on the capstan, the tape speed would increase and, since the buildup was uneven, the tape speed would become correspondingly uneven. Similarly, some units were subject to the capstan wear, causing a decrease in tape speed.
- Head alignment. This was an issue for two reasons: a) Azimuth misalignment results in reduced high frequencies, and b) Head height misalignment allows sounds from adjacent tracks to bleed over, an effect sometimes known as "double-tracking". This format, unlike other tape formats, features a movable head with four positions. Among audio service technicians, there used to be a joke that "the eight-track is the only audio device which knocks itself out of alignment four times during each album."
Another issue with azimuth misalignment is a loss of stereophonic-image accuracy. This is due to the resultant time delay between the left and right channels resulting in a degradation of phase correlation. This effect is enhanced in an 8-track system, as compared to either reel-to-reel or cassette, due to the larger physical distance, on the tape, between the left and right channel tracks. This effect could often be cured (or induced) by insertion of a match book in the player opening alongside the cartridge, shifting the alignment slightly.
Stereo 8 tapes and players developed a reputation for unreliability, mostly because of the phenomenon of having the player "eat" the tape as well as occasional failures of splicing tape. The automobile environment, with its temperature extremes, vibration, dust and so on, contributed to many failures.
The "melted" rubber pinch rollers that can be found in many early 8-Track cartridges were the result of the rubber not being fully cured. After discovering this cause, later cartridges used only fully cured (hard) rubber pinch rollers that did not deteriorate, as much, over time.
Tape tension was another cause of unreliability. Prerecorded eight-track tapes tended to hold only a single album, about 46 minutes of content, or 11.5 minutes per track. Consumers wanted the ability to record more music on a single cartridge, so manufacturers came out with units of greater capacity. With the corresponding increase in tape length, there was a greater velocity differential between the tape being drawn from the center of the reel and the tape being fed back to the outer edge of the reel as it passed the capstan/pinch-roller assembly (loop length). Over time, this would cause the tape pack to tighten, making it more difficult to feed, and to maintain a constant playback speed.
When the sliding tape pack would pull itself tight, for whatever reason, a jammed 8-track cartridge was the result. A quick solution was to hold the cartridge in one hand, facing down, while pulling out a section of, about 4-6' in length from the outer winding side. A quick tug on the tape would cause it to immediately wind in and the result was a loosened up tape pack that would play correctly.
Failing that, another solution was to open the cartridge, cut the tape at the splice, and relieve the excess tension by manually unwinding one or two sections from the outer edge of tape (loop length) while keeping the reel stationary, then re-splicing the tape, with a fresh piece of foil (since the old foil was usually caked with built-up graphite reducing conductivity and making it difficult to change tracks). Another, simpler fix was to shake the cassette in the plane of the tape reel with a rotary motion, sometimes this would cause the windings inside to rotate and loosen.
A decrease in the quality of the parts used in the eight-track cartridge, that is, plastic pinch rollers, lubricant quality and quantity, etc., was another blow to the faltering format. As problems further reduced the reliability, the sound quality, and the smoothness of the tape speed. As a result, the eight-track eventually developed a reputation for being finicky and unreliable.
Read more about this topic: 8-track Tape