Nakamichi 400 series

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I have a Nakamichi 400 series stereo that we inherited from my father-in-law. It came with a nice pair of Klipsch speakers and has served us well for the last few years. Pretty early on the tuner stopped working, but since we don't listen much to the radio I never bothered to check it out. It seems the power supply may be bad since nothing happens when you turn it on. But the really bad thing happened last night when I changed input and had the volume up too loud. It got really loud for a second and then just dead silence. I turned the volume down and you could faintly hear sound coming out of the speakers. I turned everything off and after a minute or so turned everything back on and only the left speaker was working. I thought I'd finally done it and turned everything off. This morning I was going to take the system down to open it up and the amp was scorching hot. I unplugged the power cord and let it cool down a bit. Opened it up and there is a black round object inside and it was extremely hot. I checked the fuse and the circuit boards, but could not find anythin visually odd. Now I need some help as to what I can do to figure out the damage. I'm pretty good with a meter and a soldering iron, but don't know much about how amps work. Anybody up for a little support project? ;o)

Thanks in advance,

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Sorry guys,
should have posted pictures right away, but here they are. The "black round object" I mentioned is in the center of the picture and has the number B-6553U 7FZ1 painted on it. It seems to be a cover, but I haven't taken it off yet because I want to know what I'm getting into first.
Unfortunately I don't have any diagrams of the amp, but I'm still digging around. If anyone has a lead in that regard I'd be more than grateful for the help.
Please let me know if you need more pics or info, I'll provide what I can!




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the particular amp has been described in the thread
together with the matching preamp

the particular amp features a diferent protection circuit that will somehow will have effect on power supply area ... that will probably mean that your outputs are blown or something else is causing a short circuit ...

It will also be importand to find out the facts of this amp as described in the thread since just a replacement of the outputs will not do the trick...other things need to be done also

sorry to say that this is not one of the best amplifiers that nacamichi made

regards sakis

thank you for your reply. I will check out the thread you mentioned and go from there. I know the amp is not great, but it forfilled it's purpose and definitely met our needs. And for nostalgia's sake I'm trying to get it working again as it is a reminder to my late father-in-law.
Thanks again and if anybody has any other information they can share I'd be more than grateful!


This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.