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25th December 2010, 05:44 PM
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#1 |
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diyAudio Member
Join Date: Feb 2008
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SP9 schematic questions...
I downloaded SP9/2 schematics, but my understanding needs some discussion:
I just claim what I understood, so please support / correct me! Phono: Q1: First stage V1: Second stage Q2, Q3: Cascoded fet stage (third stage) Q5,R13, R14: Mosfet source follower. My questions: Q13 seems to be for protection - why??? Q4, Q6 are n-channel jfets. Drain and source are connected - why??? Annother point is, that there cannot flow any current into the gate. So it seems they are just there "for fun". Can Anybody please explain??? Line: Q7: First stage V2: Second stage Q10, R27: Mosfet source follower. Q8, Q9 are n-channel jfets. Drain and source are connected - why??? Annother point is, that there cannot flow any current into the gate. So it seems they are just there "for fun". Can Anybody please explain??? Audio Research SP-9 MKII Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics Regs, Dirk |
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26th December 2010, 01:12 PM
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#4 |
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diyAudio Moderator
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Low leakage and capacitance during normal operation (when they're reverse biased).
__________________
“Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache |
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20th March 2012, 02:57 PM
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#6 |
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diyAudio Member
Join Date: Feb 2008
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Another point:
The schematic shows some devices denoted as: FET, WHITE ORANGE GREEN FET, GRAY BLUE FET, ORANGE GREEN FET, RED BROWN FET, WHITE ORANGE FET, ORANGE GREEN BLUE FET, YELLOW FET, YELLOW RED What are these transistors? What can I use for replacement, if broken??? Is there a substitute list around? Regs, Dirk |
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20th March 2012, 03:55 PM
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#7 | |
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diyAudio Member
Join Date: Aug 2002
Location: Sofia
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Quote:
The idea seems to be to shop for replacements from ARC or use the authorised repair facilities. Finding suitable replacements should not be difficult. Are you considering building a clone? The SP9 is not ARC's finest hour IMHO... |
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20th March 2012, 07:03 PM
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#8 |
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diyAudio Member
Join Date: Feb 2008
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Hi,
I got a broken one in my hands. I want to repair it, but I have no glue which mosfets are used. SP8 is superior, but unluckily mine is SP9... Could you recommend me the substitutes you would use? would you exchange parts on both channels??? I was told, that the power supply is broken... I'll have to check next days. My first time on high voltage stuff... |
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