Garrard 401電源供應器

這個電源供應器是按Dr Imbabi的線路製作。這個線路用韋恩電橋振盪器(wien bridge oscillator)來產生正弦波，然後用LM3886來放大並用變壓器把電壓提升到所需的水平。

The power supply is based on Dr Imbabi’s circuit. The circuit uses wien bridge oscillator to generate 50Hz sine wave and uses LM3886 power amp to drive a transformer to step up the voltage to a required level.

大部份的零件都是從深水步鴨寮街買的。LM3886, 28V 24mA 燈泡 (L1) 和 0.01uF ±1% 誤差電容(C*)則要從Farnell 訂購。

Most of the components were bought from Ap Liu Street in Shumshuipo. For the LM3886, 28V 24mA lamp (L1) and 0.01uF ±1% tolerance capacitors (C*), I had to order online from Farnell.

我用萬用板來製作，省卻蝕板鑽孔等麻煩。

To avoid the troublesome etching and drilling processes, I used prototype PCB and hardwired components on it.


完成振盪器部份。

Finished the oscillator section.




用示波器檢查。調節那個5K可變電阻直至見到順滑的正弦波。L1燈泡在這部份起了穩定振盪的作用。

After finished the oscillator section, I tested the output with an oscilloscope. The 5K VR should be adjusted to a level that nice clean sine wave appears. The L1 being part of the feedback resistors helps to stabilize the oscillation.


LM3886需要一個大的散熱片去散熱。我手上的LM3886T需要用尼龍鏍絲和雲母片來絶緣。

A large heatsink is required for proper heat dissipation of LM3886. My LM3886T is non-isolated package, so I used nylon screw and mica sheet to isolate the tab from the heat sink.



為了節省空間，我把兩組線路叠起來。

I stacked the two sections to save space.





要在機箱上開孔給IEC插座，neutrik PowerCon 接頭和電壓表。我用線鋸來開較大的孔。在鋁機箱上開孔很容易，但在5mm厚的面板上開孔就比較困難，要慢慢來。

I need to drill all the mounting holes and cut openings for IEC socket, neutrik PowerCon connector, and voltmeter. I used jeweler’s saw to cut large openings. Cutting the 5mm thick front plate is not as easy as on the aluminum case.

使用neutrik接頭因為電源線可以牢固地鎖上。

I use neutrik socket because it can securely lock the power cord.

IEC 插座附有濾波功能。

Filtered IEC socket is used to attenuate RFI.

我把100K VR裝在面板上以便隨時可以調較電壓。

The 100K VR was attached on the front plate so that I can adjust voltage easily.







完成組裝後再測試電壓和頻率。

Final testing on voltage and frequency after assembled.

完成的電源供應器。在華輝買的時候沒有檢查清楚，之後才發覺面板左上角有瑕疵。

The completed power supply unit. There is a defect at the upper left corner of the front plate. I did not check carefully when I bought it from Wah Fai.

把電源供應器接上Garrard 401。我把電壓調至190VAC，馬達比以前靜了。

The power supply unit is connected to my Garrard 401. I set the voltage at 190VAC and the motor sounds quieter.