Telefunken HiFi Studio 1 restoration

HiFi Studio 1 is portable boombox manufactured by Telefunken in around 1979. This player consists of 4 band radio (with LW, MW, SW, and FM), cassette player/recorder and with 2 × 30W audio power amplifier.

Restored HiFi Studio 1

This unit is designed using both ICs and transistors. The receiver of this unit is built around TDA1047, TBA570 and BA1320 ICs. Tape player/recorder is mainly build using NPN transistors and special Telefunken IC and 4066 ICs are used to get Telefunken's proprietary HIGH COM tape noise reduction feature. The power amplifier of this boombox is transistor based and it uses a pair of TIP130 and TIP135 transistors in its final stage.

The unit which we restored is Telefunken HiFi Studio 1 (silver) model and it had the following problems:

A unit is not powering up and completely dead.
Cassette unit is broken and some of the buttons are falling down inside the case.

After going through the circuits we figure out that the problem is with the GR501 bridge rectifier of the PSU board. We replace GR501 with KBP206 bridge rectifier module. During further checks, we note that most of the components in power amplifier board are damaged and we replace each with new (equivalent) parts. Most of the replaced components are listed below:

Original part	Replaced part
17520 (TIP135)	BD646
17521 (TIP130)	BD647
BY251	1N5408
BD373	BC338
BC637	BC338
BC338	BC338
0.47Ω resistors	0.47Ω 3W resistors

Apart from the above components, we replace all the electrolytic capacitors in the power amplifier board.

Partially restored power amplifier board.

In cassette mechanism problem is with the button bar axle and we fix it by attaching 3D printed plastic holder into cassette mechanism's body. Also, we replace playback/record head and pinch roller of this mechanism, and after that, the cassette unit starts to work again.

HiFi Studio 1 test setup (without cassette mechanism)

Restoration of this Telefunken HiFi Studio 1 takes more than 3 weeks because we replace more than 45% of parts in that unit. After the above fixes, this boombox starts to work again. Unfortunately, we don't have matching speakers for this unit and we test it with some 8 inches 2-way speaker system. The sound quality of this unit is impressive and we really like it's "unique" cassette unit.

Comments

strudbald said…

Is there an equivalent new part for the transformer unit?

September 22, 2020 at 12:28 AM

CD2003 - yet another simple FM radio receiver

In the last few days, we are looking for some simple FM radio receiver to integrate into one of our ongoing projects. For that, we try several FM radio receiver ICs including TDA7000, CD2003/TA2003/TA8164, CXA1019, and KA22429. Out of all those chips we select CD2003 (or TA2003/TA8164) based receiver for our project because of its simplicity and outstanding performance. Except to CD2003, Sony CXA1019 also perform well but we drop it because of its higher component count. We design our receiver based on Toshiba TA2003 datasheet and later we try TA8164 and CD2003 with the same circuit. Either CD2003 or TA8164 can directly replace TA2003 IC, and as per our observations, TA8164 gives excellent results out of those 3 chips. A prototype version of CD2003 FM radio receiver The PCB design and schematic which we used in our prototype project are available to download at google drive (including pin-outs of crystal filters and inductors ). Except for CD2003 IC, this receiver consist...

Arduino superheterodyne receiver

In this project, we extend the shortwave superheterodyne receiver we developed a few years ago . Like the previous design, this receiver operates on the traditional superheterodyne principle. In this upgrade, we enhanced the local oscillator with Si5351 clock generator module and Arduino control circuit. Compared to the old design, this new receiver uses an improved version of an intermediate frequency amplifier with 3 I.F transformers. In this new design, we divide this receiver into several blocks, which include, mixer with a detector, a local oscillator, and an I.F amplifier. The I.F amplifier builds into one PCB. The filter stage, mixer, and detector stages place in another PCB. Prototype version of 455kHz I.F amplifier. In this prototype build, the Si5351 clock generator drives using an Arduino Uno board. With the given sketch, the user can tune and switch the shortwave meter bands using a rotary encoder. The supplied sketch support clock generation from 5205kHz (tuner f...

Calculator for audio output transformers

Audio output transformers are heavily used in a vacuum tube and some (older) transistor base audio power amplifiers, but these days output transformer are quite hard to find and expensive item. For homebrew projects, the best option is to construct those transformers by ourselves and this script helps to calculate winding parameters for those transformers. This " AF output transformer calculator " script is written using Python and it works with most of the commonly available Python interpreters . The script is available to download at google drive under the terms of GNU General Public License version 3.0 . Homebrewed 25k: 4 output transformer Once supplied the input parameters this script provides a winding ratio, the number of turns required for primary and secondary winding and required copper wire gauges for both primary and secondary windings, etc. We construct several AF output transformers based on results of this script, which including transformers for M...