Nakamichi PA5E MK II service manual / schematic - diyAudio
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Old 25th August 2011, 08:29 AM   #1
Nrik is offline Nrik  Denmark
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Default Nakamichi PA5E MK II service manual / schematic

Hi

Does anyone have this ?
I can easily find PA5e mkI and PA7, but not PA5e MKII.

There are two trimmers on each channel ( only one in MKI)... wich on is idle current/Bias, and what does the other do ? (DC-offset? - or bias for the extra 4 transistor-pairs?)
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Old 1st September 2011, 06:57 PM   #2
Nrik is offline Nrik  Denmark
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No one ?
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Old 16th September 2011, 08:05 AM   #3
Nrik is offline Nrik  Denmark
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Okay so thanx for nothing guys no it's okay.

I never found any servicemanual, schematic or adjustment procedure, so I had to reverse engineer the whole shabang and calculate decent standing currents myself.
Note the schematic and adjustments are somewhat different for the other models PA5, PA7 and PA7mkII, so please use this only with PA5EII and maybe the non-european version PA5 mkII.

So I will here share my findings in case someone else will need to adjust his/hers Namaichi PA5EII.
This procedure gives approximately 10mA through drivers Q114+Q115, 115mA through each output-transistor Q116-Q119 and finally 40mA through each CFP-secondstage output-transistor Q120-Q127.

I read about some people who where bumping up the current to gain more class A sound. Eventhough the heatsinks seems to be able to handle it, I will strongly recommend you to keep the original settings. The CFP/sziklai output stage is superstable and seems in perfect symmetry at these settings. But if mess with it, bad things could happen.

Here is how to do it.
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File Type: jpg adjustmentprocedure.jpg (68.6 KB, 293 views)
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Old 16th September 2011, 08:21 AM   #4
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be nice to people here ...most of the times are very helpfull .... your post has 139 views including mine ...that also means that i took a few minutes to check my resources and had the same results with you(138 other people did the same !!! ) ...seems that documentation for your amp is very hard to get .

your procedure is correct and the information you provided is the best so far ...t5hank you for that

kind regards
sakis
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Old 17th September 2011, 03:15 AM   #5
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Best I can offer other than basic specs if needed.
Doc

http://i1112.photobucket.com/albums/...doc/NakPA7.jpg

Oops... not much help. But since I set up the link I'll leave it.
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Last edited by thaumaturge; 17th September 2011 at 03:35 AM.
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Old 18th December 2011, 02:50 PM   #6
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Hi,

i adjust my PA5E II with your informations and sounds like good but i think the temperature is to slow. Can it be? I read the temperature on heatsinks must be 50 degrees.

best regards
chris
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Old 18th December 2011, 06:33 PM   #7
Nrik is offline Nrik  Denmark
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slow or low ?
Don't mind the temperature - it doesn't need to be anything specific, and if you play some music with moderate volume the temperature will increase. The temperature is a biproduct of the standing current, and this is the important parameter.

If you have the indicated voltages +50%/-30% at the testpoints, then your amp is working as it should.
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Old 18th December 2011, 10:35 PM   #8
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oh sorry i mean low and not slow...
ok then its all good and the amp is working perfect.
thanks
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