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Sony DDII Walkman and Small Fix

I recently bought this beautiful Sony DDII walkman. Nice metal body. Very well made. It utilizes a special disc-drive mechanism with a thick rubber ring (replacement available at fixyouraudio.com) instead of a  normal belt. Thanks to that, it has very low wow and flutter (mine is about 0.05%). It is also the first walkman that incorporates a Dolby noise reduction chip at 3V (without upconversion). The walkman is just a bit wider and longer than the tape itself and about twice as thick. Truly a marvel of engineering.

The DDII has two headphone jacks and is capable of driving headphones with impedance up to 300 ohms. The play button is interesting. By pressing it, it does not directly engage the tape head. Rather, it just pushes the mechanism to the right position while the main motor starts spinning. This process drives and engages the tape head. I would like to call it mechanical softtouch control. Very satisfying to push. 

Sony DDII walkman (photos added later from 2021, Dec.)
Sony DDII walkmanSony DDII walkmanSony DDII walkmanSony DDII walkman

Opening the case reveals the disc-drive mechanism (bottom left).
The long cylindrical tube on the left is the motor.
Top right are the blackube batteries which ensures a constant voltage 3V.
Sony DDII walkman

The DD series are known to have a small design flaw: the center is designed with metal at the center and plastic gear on the outer ring. Because of such design, temperature fluctuation can cause tension and potentially crack the plastic outer ring due to the different thermal thermal expansion coefficients of the materials. That said, in practice, it takes a long time before the cracking happens (like more than a decade). And lucky for me, mine has been refurnished with a new center gear. It should be good for a long time.

People say it is less common for DD walkman to have circuit board issues thanks to the use of ceramic capacitors and generally good circuit design. However, for any gadget of that age, anything can happen. Unfortunately for me, mine has an issue as well: the Dolby NR stopped working. The switch did absolutely nothing. The reason was that the trace (on PCB) that connects the one end of the Dolby switch and the ground of the volume control wheel was broken. The thing is, that part is buried under the volume control wheel. It took some time before I tracked down the issue. Luckily, this can be repaired easily by soldering a new wire (there isn't lots of space to work with though).
Sony DDII walkmanSony DDII walkmanSony DDII walkman


2/5/2020:  There is something wrong with the headphone jack. As you can see, there are lots of cracks underneath (the picture was taken after superglue was applied). The plastic is very much weaken after such a long time. Again, this is not something you would notice until you desolder the whole thing (by using lots of desoldering braids). A symptom was that one channel of the audio output got disconnected sometimes. By the time I realized the problem, the crack already extended all the way outside. Ideally, we would simply buy a new headphone jack, but in this case, I applied some super glue as a quick fix. We probably can't find a matching one anyway.
Sony DDII walkman

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