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Nakamichi PA 5 II Resistor
Nakamichi PA 5 II Resistor
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Old 9th November 2017, 01:10 PM   #1
fantacrazy is offline fantacrazy  Italy
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Default Nakamichi PA 5 II Resistor

Hi i have a problem with a channel. I found only a R on emettitor burned Only R (i Think autooscillation), manual service tell me replace with a fail safe (1 ohm 2w). I have replace it with a metalized flameproof, make low voltage test, and all ok, so i have assembled and iíll read perfect bias (40mv) for 20 minutes then dropped to 1,5mV and I find all the resistors that measure even 1.8/2.5 ohm (1 ohm) and some interrupted and now There Is only one final transistor burned.
Everything is perfect. In attachment there is PA 7 but is same project
What is the problem? Metallized R is Not ok??
Thank you
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Last edited by fantacrazy; 9th November 2017 at 06:45 PM.
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Old 10th November 2017, 03:02 PM   #2
fantacrazy is offline fantacrazy  Italy
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Nothing to do. I change R with wirewound and one final transistor. power on and no error, relay close and start, but if i search to set 3,9V on TP3, R of check burn and smoke... i just check every diode transistor R Cap and it’s all right.
Is possible that final transistors also if good to be “burn”?
Can you help me?
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Old 16th November 2017, 12:44 AM   #3
djk is offline djk
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The schematic has part numbers on it, it would be helpful if you would use them.
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Old 16th November 2017, 06:50 AM   #4
fantacrazy is offline fantacrazy  Italy
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Quote:
Originally Posted by djk View Post
The schematic has part numbers on it, it would be helpful if you would use them.
Hi i solved, also if problem is manual service because pa 5 II is same pa7 II so i need rebuilding for me schematic in a paper.
the problem was on dual fet input 2sk that over heat change status and oscillated.
there are no more forums than once

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