唱盤橡皮帶回春

Jim這台Dual LP player made in West Germany大約是1978年的產品。

它原來爛掉的貼皮"甘蔗板"框架 給壓克力美工店換了之後，黑漆漆的，倒很漂亮。

Jim說啟動時有些怪聲、唱唱有時候會有一個聲道斷掉，拿來要給 Dr. Dual wouldbe看診。

只要鬆開3個勾環螺栓，附有4個彈環腳的盤面可以脫離底座，

轉盤是卡筍鎖住的，要先鬆開螺絲，把卡筍外推。

這是固定轉速的8極馬達，經過橡皮帶，間接驅動轉盤的。

構造比起之前拆過的Dual 606簡單多了。直接驅動馬達的606如下。

 

馬達轉動軸心，直徑上小33  rpm、下大45 rpm 用的。靠右邊白色的撥桿將皮帶上、下定位。

鋁鑄的轉盤重 1.3 kg，算是中量級的。

照片是轉盤的底面。

裝回去的時候，要先把皮帶套上轉盤底下的圓環 ，再翻轉過來，轉軸對準盤面的承軸套孔壓上去。

可是黑色的橡皮帶 年老力衰，鬆垮了，掛不上，無法裝回去。

量一下圓環直徑是180 mm，周長=3.14*180=566 mm，對半是 283 mm

皮帶已經鬆垮，量一下對半是 280 mm, 總長超過 300 ＊2= 600 mm,  需要縮緊 600-566＝34 mm。

縮緊 34 mm 可算是艱難的任務。

我把皮帶放在茶杯裡，像沖茶一樣，沖入90度的開水，放個半小時，讓它自然冷掉。

這樣連續3次，皮帶縮緊，已經可以套進圓環，成功回春了。

這招幾年前，在Thorens 295的老皮帶做過，證明可行。

其道理，本人學化工的理解是：

固態物體有"結晶態"crystalline state，極端的 可以拿彈性的橡皮筋為代表，還有"不定型態"amorphous state其實也算是高黏度的液態固體，極端的 可以拿又脆又硬、沒有彈性的玻璃為代表。兩態之間有個 "過渡溫度" glass transition temperature。

把橡皮加熱超過transition temperature，再冷下來，讓它重新結晶，恢復彈性，也許像煮麵條一樣，在鍋子裡會更有效。

如何掌握、控制兩態的比例分配，就是康寧玻璃不容易破裂的商業機密了。

參見維基

http://en.wikipedia.org/wiki/Amorphous_solid

An "amorphous solid" is a solid in which there is no long-range order of the positions of the atoms. (Solids in which there is long-range atomic order are called crystallines or morphous). Most classes of solid materials can be found or prepared in an amorphous form. For instance, common window glass is an amorphous solid, many polymers (such as polystyrene) are amorphous, and even junkfoods such as cotton candy are amorphous solids.

In principle, given a sufficiently high cooling rate, any liquid can be made into an amorphous solid. Cooling reduces molecular mobility. If the cooling rate is faster than the rate at which molecules can organize into a more thermodynamically favorable crystalline state, then an amorphous solid will be formed. Because of entropy considerations, many polymers can be made amorphous solids by cooling even at slow rates. In contrast, if molecules have sufficient time to organize into a structure with two- or three-dimensional order, then a crystalline (or semi-crystalline) solid will be formed. Water is one example. Because of its small molecular size and ability to quickly rearrange, it cannot be made amorphous without resorting to specialized hyperquenching techniques.

Amorphous materials can also be produced by additives which interfere with the ability of the primary constituent to crystallize. For example, addition of soda to silicon dioxide results in window glass, and the addition of glycols to water results in a vitrified solid.

Some materials, such as metals, are difficult to prepare in an amorphous state. Unless a material has a high melting temperature (as ceramics do) or a low crystallization energy (as polymers tend to), cooling must be done extremely rapidly. As the cooling is performed, the material changes from a supercooled liquid, with properties one would expect from a liquid state material, to a solid. The temperature at which this transition occurs is called the glass transition temperature or T_g.

 

 15th Sept後記：

拿回家接上唱放，發現是有怪聲，最後還是"脫褲子".

乾脆換上一條265 mm皮帶，取代原來 280mm的鬆帶。

用Grado MM唱了幾張LP，是非常棒的聲音，不會有石磨子唱盤+AT-OC9 MM唱頭乾乾瘦瘦的感覺。