I was able to buy some service manuals from a radio repair shop in Austria which, unfortunately, ceased business. There was a little hope that it contains all pages inclusive chapter 9 (modifications). Unfortunately chapter 9 was missing and I really think it was never written. It seems there is no documentation available for the changes, so the PCBs often […]
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Workplace update
During analysation of the second unit I noticed that I need a frequency generator to be able to measure the audio channels. Real measurements based on a connected music box will not lead to any success. I came up with a cheap Chinese frequency generator. It delivers accurate results and offers a lot of feature for its price. However, its […]
Power Supply Issues
A first measurement of the voltages has shown that +9V and +5V are missing because of a broken fuse (1467). After ordering some spare parts – basically trying to get every component of the PCB – I replaced the fuse 1467 and also removed the transistors 7477 and 7478 of the same supply line. Testing has shown that they are […]
Evaluation of Unit #2
Whilst one sound machine is working – more or less, not perfect but I will take care about later – I have done an analysation of the second unit and the issues. First, when switching on the device the power LED is not working. The background LCD is working and the cassette part shows all options. There is no reaction […]
Unit #1 finished for the moment
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 […]
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 […]