ZRK M2045S Tape Recorder

I got this device as an old attic discovery from one of my friends. He claimed, there are a several problem, but mainly with driving a tape, not working rotation counter and crakling potentiometers. When I took off a plastic cover, it turned out that there will be much more work to do. I had to start with cleaning everything inside. I found some spiders corps and nets, dust and also rust and old grease. When this part was done, I took potentiometers as a first point.


This tinny metal box is a little version of Pandora's box. Extremally stuffed with electronic and very tinny, shielded signal wires didn't allow for playing with them eaisly. I had to be careful also because of theirs age. In such case it is good to have original schematic and take some pictures. I can't even recall in my mind how many times, picture of some detail resqued me before long hours spent over schematic, searching in the Internet and stress during first connect. As a first, I opened sliding potentiometers. I noticed, that not much left from theirs covers. I expected, that they will be realy dirty, but not that much. So I cleaned, greased and assembled them back. I couldn't do more. I looked in the Internet for replacement ones, but they are not avilable. So what was done, must be enough.


Since I have electronic elements tester which is able to check capaciters, I can't resist a temtation of checking them in the most crucial parts of repaired device. Sometimes I'm checking all of them. This time I checked those from preamplifier and I must say it was worth. Two of them needed to be replaced.


As a first, I had to put brand new rubbers. Due to years, they have lost its flexibility and one of them has just fall in a parts. This was a main reason why rotation counter wasn't working. Fortunately full set of them are still available, so I have ordered them. As a next, I disassembled all parts that allowed for that, cleaned and greased them. Brake of one roll was loose and tape was kneaded by the driving mechanism. Fotunately, producer had considered this case and mounted some adjusting parts.

Power supply noise

It is one of the worst things to eliminate in devices. I also got a feeling that this is the worst problem in this model. Thanks to the Internet, I got know that engineers, that designed this product, had made all their best to eliminate this problem. Very interesting parts are coil antenats put on inputs of some circuits, gathering internal noise and subtracting from the signal. I decided to take an effort to elimite it as much as possible. When I took a closer look to power supply, expecting that main capacitor may be dry or demaged, I have been shoked. Printed circuit board wasn't original and was only adopted to power supply purposes. Main capacitor was hanging on one wire. Power transistor has one leg almost short circuited to 230V. A disaster. If I had more time, I would probably made a dedicated PCB. Unfortunately, I had to resque what was there. I fixed all problems, isolated leg, resoldered connections and cleaned PCB. After that, noise got a bit smaller, but still I couldn't name this tape recorder as a silent one. Probably becase of big motor in the middle of not shielded circuits.

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