Import heads in domestic tape recorders. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Import heads in domestic tape recorders. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Audio equipment

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In recent years, the home appliance market has almost completely shifted to selling imported equipment. For the majority of consumers, CD players, unfortunately, remain inaccessible. They buy more cassette tape recorders, radio tape recorders, "decks" - tape recorders-prefixes (MP). Among them are many high-quality models from companies such as Sony, Aiwa, Technics, Pioneer, etc.

Recently, many people are trying to sell their tape recorders, which 3-4 years ago were considered the highest quality in our country (for example, MPs of the first complexity group of the Vega or Morion brands). But they are inferior to foreign ones, mainly in design. The circuit solutions of these devices are often no worse than similar imported tape recorders. When purchasing radio equipment from Japan and Korea, not everyone knows that it is most often assembled in China or Singapore, Thailand or England. And if after six months or a year the product fails, the owner is left with only disappointment and a "beautiful body". The repair of such equipment is very expensive.

Meanwhile, after a simple revision, some parameters of domestic tape recorders can be improved, bringing them to the level of high-quality imported MCs. The most noticeable result is the installation of a universal magnetic head from Aiwa. Replacing heads with others - domestic or imported - requires the selection of capacitors in the input circuits of the reproduction amplifier due to the difference in the inductance and resistance of the windings. In addition, some heads do not match in size and location of the cores relative to the magnetic tape.

Aiwa universal magnetic heads - their full designation "HFHD Aiwa", appeared on sale at the end of 1996. According to the main characteristics (inductance, winding resistance) and installation dimensions, they are fully suitable for our "Vegas" and "Morion". The soldering of the windings to the leads also corresponds to the sendust heads. That is why they were given preference.

Tests of modified tape recorders showed (a total of 10 sendast heads were tested in MP "Vega MP - 120S", "Vega MP - 122S", "Morion MP - 101S" and "Morion MP-101-1S") that on a magnetic tape type IEC I the bandwidth of the recorded frequencies without distortion reaches 17,4 ... 17,8 kHz, and on IEC II - up to 18,2 ... 18,6 kHz. With a wider frequency band, a non-linear frequency response occurs. The installation of such a head improves the quality of the phonogram: the treble drop is excluded during recording, the copy is almost the same as the original.

In particular, a two-cassette MP "Vega MP-122S" was tested. Heads "HFHD Aiwa" were installed in the LPM. Before the reworking of the tape recorder, when copying magnetic phonograms at normal speed, a slight treble drop is obtained, which is even more noticeable at double speed. After installing new heads, when copying even at double speed, losses at higher frequencies are almost imperceptible.

In particular, the quality of the recording on the modified "Vega MP - 122C" and one of the MP "Technics" from the CD player "Vega PKD - 122C", assembled on the element base of the Sanyo company, was compared. To record the control phonogram, a high-quality laser CD - "DDD" (digital recording and replication path) was used. The sound quality of the CD itself and the recorded copies on IEC I and IEC II magnetic tapes were also compared. Listening was carried out through the amplifier "Technics - 500" and loudspeakers of the same company with a power of 100 W and with a band of 20 ... 25000 Hz. The quality of the recordings subjectively almost did not differ. The only but significant difference was that on the "Technics" deck, when overdubbing from cassette to cassette, the high-frequency level is automatically raised, and therefore the copy practically does not differ from the original.

The universal head "HFHD Aiwa" was also tested in the Mayak-233S cassette recorder, released in 1991. The resulting effect turned out to be amazing: even when played through its "control" loudspeakers, the sound became much cleaner and softer than before the replacement of the ZD24N.221 head. The treble level has noticeably risen and the "mumbling" on the bass has disappeared. Thus, the recommended magnetic head can be installed in almost any domestic cassette recorders and set-top boxes, and get excellent results at relatively low costs (now "HFHD Aiwa" magnetic heads are sold in stores at a price of 35 - 40 rubles).

To further improve the quality of the MP, it is advisable to replace the playback amplifier on the K157UL1A chip with a more advanced one. The magazine "Radio" described several such hydrocarbons in 1994 - 1997. Based on the element base available to the radio amateur, you can choose the appropriate option. In most domestic MPs, the playback amplifier is assembled on a separate printed circuit board connected to the cross-board through a connector, so you do not have to make changes to other tape recorder boards.

A new UV is assembled on a separate board, close in size to the one being replaced, the contact pads are brought to the corresponding connector contacts. The connector itself is carefully unsoldered from the old board, using a soldering iron with solder suction or using a sharpened medical needle from a syringe, and transferred to a new board. Thus, the MP "Morion-MP101S" (analogous to "Vega MP-122S") was finalized. Together with the new head, two versions of the UV were assembled and tested: the first - on the K157UD2 op-amp, and the second - on the K548UN1A IC with non-standard inclusion. Both showed excellent results.

Author: A. Suvorov, Perm

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