The stereo tape recorder TK 27 L with a defective track switch

The TK 27 L is a 4-track stereo tape recorder from Grundig, equipped with tubes (2x EF86, 2x ECC81, EM84, EL95). Its operation and features are kept quite simple and straightforward. It was a device from a very popular series of Grundig tape recorders. It only had seven buttons, two knobs, and a rotary switch - that was it. Even the tape counter was not included as standard in this series. But this does not mean that these devices are of poor quality. On the contrary, since the repair, this device has been producing quite decent recordings, and the playback through the built-in speaker is also quite good. However, this particular unit had a few serious issues when I received it.

An overhead view of the interior shows that the playback function worked after the "motor repair," but the recording function did not. Although the magic band showed an input level, the subsequent playback revealed that the old recording had not been erased. The new recording was only heard as heavily distorted. In the picture, you can see that I connected the oscilloscope to the erase head, but it did not receive a signal from the erase oscillator.

Seen from below, the opened device shows the motor bracket, which is not original. It was made of die-cast zinc or something similar, and it was broken into several pieces. After removing it, I modified and installed a motor bracket from a faulty Telefunken device, which now holds up well and works perfectly.

After some time spent searching for the problem, and spraying the recording and playback switch contacts with Ballistol, the recording function sometimes worked and sometimes didn't. It was only after a careful cleaning of the contacts and the track switch that the problem was finally solved (for the time being).

Finally, a look at the amplifier board. The EL95 for the power amplifier is visible in the upper right corner. This tube serves as an oscillator tube for the pre-magnetization frequency during recording.

In conclusion, I would like to make a few remarks about this Grundig device series.

My first tape recorder, which I received as a gift in 1984, was a TK 14 L, a two-track mono device. I owned it for about 23 years, and during that time, I never had a single defect with this device, even though it was no longer new at the time. Later, I acquired a TK 19 L, and this device also worked perfectly. The device shown here had the described recording issues and a broken motor bracket, but there were no broken belts or worn rubber parts. All of this seems to be uncommon for Grundig, unlike many devices from other brands that I have seen and repaired. The devices have a mechanical design that still works flawlessly even after 40-50 years(!). Additionally, the magic band still has a very good brightness. A stereo recording made with this device sounds clear and clean, like it would with much more expensive machines. I had to mention this because I have seen these beautiful devices being somewhat belittled on various websites.