During the last days I reassembled unit #2. Of course it was not as easy a I thought. First problem was my CPU replacement board which builds too high to have enough space between the uProc and the cassette panel. However, I had a third PCB and completed it with elbow connectors and lower IC sockets. Furthermore I removed the inverted part which I used to drive the clock of the CD-Player CPU. For an unknown reason it was not working stable on my replacement board whilst it was on the experimental boards.
When finished the boards fit smoothly and fine. But (there is always a but) the cassette deck was not working probably anymore. When using the direction right to left the mechanics always stopped. I figured out the tape reader sends a signal for what reason ever. After several hours I noticed the cable for the sensors of the tape mechanics had loose contacts so I had to crimp all the cables again – almost all cables had loose contacts. Unfortunately it was not solving the issue. Later I traced it down to an issue with the timing of the source code for the new CPU when reading the sensors. The pins to read the contacts of the keyboard and sensors need some time to rest. I added a wee delay and finally the tape deck is able to playback, to search for music, to be programmed and so on. The last thing that needs to be checked is recording. Although already programmed in the source it is not fully tested and can only be tested when everything is assembled since we need SK15 of the cassette panel to switch between play and record.
However, it sounds easy but again, when switching on record the fusible resistor 3404 burns and supply F2 is gone. So I had to replace it several times. In the meantime I put the resistor on top of the mounted board for easier replacement. Right now I had not enough time to find the issue. My first guess is the switch SK15 which might cause a short circuit.
In the meantime I am doing a long time test and the unit runs now for several hours. One improvement is on my list: to add a bluetooth module to use the sound machine as a speaker. The module should arrive tomorrow.
At the end there are some minor issues left:
- On segment of the LCD-Panel at the CD-Player is always on
- CD-Player sometime need several tries to play a track, especially track 10 or above
- Rewind is sometimes slow – which might be because of the replacement gear which is not working perfectly
- Click on record kills the fuse 3404
