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Old 6th February 2014, 01:23 AM   #1
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Question bias on sansui au555

help me,i don't known the simillar or equavalent the transistor cdc9002-1,there was broken,the complementary cdc8002-1 is normal,
how to make setting bias sansui au 555 with simple and correct?
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Old 6th February 2014, 05:09 AM   #2
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Sansui AU-555 | Owners/Service Manuals, Schematics, Free Download, Reviews | HiFi Engine
http://www.vintageshifi.com/sansui-555-a-2.php
It may be obvious but you'll find the bias settings in the service manual. These links are to info. for the for 555A, which has an extra tone control and different paint, but otherwise the same.
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Last edited by Ian Finch; 6th February 2014 at 05:29 AM. Reason: add equivalents link
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Old 6th February 2014, 06:41 AM   #3
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Quote:
Originally Posted by Ian Finch View Post
These links are to info. for the for 555A, which has an extra tone control and different paint, but otherwise the same.
Not quite. Both types are shown in the Hifiengine list of documents. The, components are different, and you quoted AU555A model parts.

If you actually have this 555A model since you refer to 9002-1, the PNP driver, you will need to find a better equivalent than the suggestion I posted above. Instead, replace both drivers with roughly matched Hfe BD139/40 types, to reflect the designer's intention, whether that's right or wrong. Your choice, but if a driver has failed, check the output transistors too.
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Old 8th February 2014, 01:53 AM   #4
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i want to try 2SB560+2SD438 to replace it,thanks for your advice.
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Old 8th February 2014, 01:56 AM   #5
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when i set bias about 5mA,the sound more relax,not make ear fatique.
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Old 8th February 2014, 07:36 AM   #6
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Which model are you talking about, hersp13 - AU555 or AU555A?

There are different case styles of 2SB560/A438 available. Some are probably OK for a 25W EF amplifier driver, as used in the AU555A but others will fail because their tiny TO92 size case cannot dissipate the necessary heat. The higher you set the bias level, the more heat dissipation is caused.
SANYO - datasheet pdf

There will also be fakes of these TO92 styles because they are so easy to re-label. It's your risk and if your interest is based only on listening impressions, then I guess you will do as you please anyway, but be aware that you can do worse damage than just burn the drivers when they fail.

I'm also curious that you ignore the instructions for bias setting which is 20 mA total current through each amplifier fuse. You have quoted 5 mV but not where you measured it, what it measured originally nor why you changed the method. Are you talking about the original amplifier(s) or something else?

It would also be helpful if you answered questions, where you can.
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Last edited by Ian Finch; 8th February 2014 at 07:41 AM.
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