review33.com: 影音天地: etsang3 修理 Marantz PM5

分類搜尋 移民 | 借錢 | 投資 | 物流 | 搬運 | 按揭 | 樓盤 | 保險 | 機票 | 酒店 | 升學 | 補習 | 手錶 | 電腦 | 紅酒 | 網購 | 脫髮 | 健身 | 減肥 | 濕疹

影音天地主旨 ﹝請按主旨作出回應﹞ 上頁首頁

寄件者

傳送日期

[#21] etsang3 修理 Marantz PM5 wo hing, the fixed BIAS resisters I mean are the 4.7k and 15k (near the Class A switch) above. After the Power Transistors are replaced, the voltage drop across the Re (usually 0.2Ωto 0.5Ω at the E leg of power Transistor) must be checked. e.g if it is 0.22Ω/5W resistor and a bias current of 100mA (0.1A) is running. The voltage measured at the resistor's 2 ends will be 0.22 x 0.1 = 0.022V=220mV. To ensure there will not be crossover distortion due to light BIAS. I always adjust the BIAS to 200mA (idle current).		etsang3 正式會員 219.xxx.xxx.159	2008-10-26 18:22

[#22] etsang3 修理 Marantz PM5
Ok, etsang3 sir

Assume the 0.22ohm resistor is normal, in case the voltage across 2 legs of 0.22ohm resistor is not 200mV, that mean we have to adjust either the 4.7k or 15k ohm in this case?

Also, 200mA (idle current) is universal or should refer to transistor spec?? I have impression some amp requie 300mA for this (school time amp...) THX

正式會員
58.xxx.xxx.90

2008-10-27 01:06

[#23] etsang3 修理 Marantz PM5
....that mean we have to adjust either the 4.7k or 15k ohm in this case?

＞＞Yes. The higher the resistor value the higher the BIAS current will be.

Also, 200mA (idle current) is universal or should refer to transistor spec?? I have impression some amp require 300mA for this (school time amp...)

＞＞Ng~ I think the minimum is 100mA. Lower than that you can "SEE" Crossover Distortion at the CRO. You can set to 300mA or even higher and the sound will be better provided the heatsink is OK to keep the temp. below 60C.

When Power Transistor reach that temperature, its power handling capability (before it die) actually dropped to half of the spec.

etsang3

正式會員
202.xxx.xxx.193

2008-10-27 13:19

[#24] etsang3 修理 Marantz PM5
The power transistors will be replaced with 1302 and 3281 for replacement (all old one tested with leakage ???).
Will update here later.

etsang3

正式會員
202.xxx.xxx.193

2008-12-17 09:03

[#25] etsang3 修理 Marantz PM5
我呢部 PRE-AMP 中間果排五個選擇制中, 最右邊果個制接觸不良, 唔知有冇得換 ?

薯麥

正式會員
218.xxx.xxx.21

2008-12-17 19:23

[#26] etsang3 修理 Marantz PM5
唔知仲有冇呢種制買 ?

薯麥

正式會員
218.xxx.xxx.21

2008-12-17 19:34

[#27] etsang3 修理 Marantz PM5
I think we cannot get this type of switch even when the amp is release to the market. Those were tailor made. However, we can opoen the switch to fix the probelm. Most of the time, it just get dirt inside. Did you spray contact cleaner at the switch to try fixing it ?

etsang3

正式會員
203.xxx.xxx.9

2008-12-17 21:53

[#28] etsang3 修理 Marantz PM5
Not spray at the RED circult you marked.
Spray at the other end (follow the blue tape) and turn it many mnay times.

etsang3

正式會員
203.xxx.xxx.9

2008-12-17 21:55

[#29] etsang3 修理 Marantz PM5
many thanks !!!!!

i will try it.

薯麥

正式會員
218.xxx.xxx.21

2008-12-17 23:43

[#30] etsang3 修理 Marantz PM5
etsang3 師傅

真係得, 而家全正常了. 謝謝 !

薯麥

正式會員
218.xxx.xxx.21

2008-12-21 21:28

[#31] etsang3 修理 Marantz PM5
ha..ha.. very happy.
another one fix his own HiFi.
It's more happy than fix by me.
When you play music, you will have the feel be a conductor la.

etsang3

正式會員
219.xxx.xxx.82

2008-12-21 23:56

[#32] etsang3 修理 Marantz PM5
etsang3 師傳
在這堶伬茼a方問下野
我部合併石機正中是火牛牛兩邊各一排散熱器我發覺兩邊的溫度都不同一邊暖一邊是微暖還有機頂有小雪L振但聽聲及長開10個鐘都沒有出現甚麼問題請問這情況是否正常的?
謝謝!

ECC83

正式會員
203.xxx.xxx.97

2008-12-26 11:18

[#33] etsang3 修理 Marantz PM5
ECC83兄,
可否打開裴ost一D相上黎睇下呢?一般黎講,牛在中央,機內佈置左右對稱,機外左右雜物阻擋氣流一樣,左右散熱器的溫度應是一樣的,左右散熱器溫度不衡會是偏流(BIAS)失調所致,你有他表的話可以量度每個"輸出管"的瓦阻(白色方型電阻)兩端得出的電壓降,看看是否一樣(+/-10%內)。
注意:在不開電的情況下用苳M刮得各電阻腳一般乾淨,以方便量度。電表設定在DC=2V檔(一般會量得0.01-0.1V),量度時小心不要踫到其他零件腳,上身不要帶金屬物(手錶、頸鍊等),如果你是"新手",最好帶埋膠手套。