Finally I reassembled everything and added a missing connector from the right speaker. In the beginning, the CD Player sometimes moved the head up and down without reading the disc. However, after some hours of playback it never happened again. Maybe there are some capacitors that need replacement? Unfortunately it seems the FM-Tuner does work since it is not possible […]
Category: Unit 1
A sound machine full of miracles
The last days I designed the PCB to replace the original tape deck CPU with the ATmega1284P. After ordering the PCB I decided to run the hardware self-check of the CPU – the circuit can be found in the datasheet – to evaluate what part of the CPU is broken. Since I have not had a 10MΩ resistor I had […]
Troubles with the slide servo relay
From time to time the slide servo relay does not switch. Till now I was not able to figure out the reason. By using the original circuit with the darlington amplifier of 7523 and 7516 the relay does not react in any way. A fun fact is that the delivered 12V are not converted into 5V (G & G1) but […]
Getting familiar with the tape deck mechanics
To be able to rewrite the code for the CPU I need to understand how the tape mechanics work. Unfortunately I was not able to get the service manual SER-1/5603 which contains the required information. Therefore, I it was necessary to do a reengineering of the mechanics. I surely disassembled the mechanics a thousand times to analyse its functions. In […]
Replacing the CPU internal resonator for the clock speed
LThe tape deck CPU generates the 5.3MHz which are also used by the CD CPU. This it is necessary to keep the resonator and find a replacement in the final circuit. During the first tests I used the old CPU just to generate the required clock speed. However, it can easily replaced by an inverter gate in a 74×04 logic […]
Writing the LCD driver
First step of replacing the tape deck CPU is to write a driver for the LCD display to be able to see what is going on. The display consist of two MM5452N, serial lcd drivers which are still available nowadays. Checking the display is also a good change to proof if the hardware is working and if that may caused […]
Replacing the tape deck CPU
As the analysis has shown the tape deck CPU is broken and I am going to replace it with a modern 8-Bit Risc CPU, the Arduino. Since the tape deck CPU controls the Play/Stop/Pause buttons of the CD-Player I get, in the first step, the keyboard working. To get the pressed buttons a matrix of eight output and three input […]
A first analysis of broken things
Well, after studying the service manual for a couple of days and after some measurements I got a first impression of what is broken. The three keys for the CD-Player Play/Stop/Pause are controlled by the tape deck CPU. As we have seen that no key of the tape deck shows any reaction I have a suspicion. To check if I […]
Checking the power supply
The first step is to measure if the power supply is working. The time I started with the documentation of this website I have already done this step so I can explain in detail the problems and workarounds in a singe post. The power supply consists of seven main supplies. However, several boards do have additional circuits (e.g. 78xx) to […]
The initial situation
What issues do the sound machine have? As I already stated in another post I have now three of them all showing the same issues. Based on the following four sections I am going to add the current state on the main page. AM/FM Radio The radio is working fine. It is possible to receive signals although it is quite […]