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Nikko Alpha 450

M

Microcontrol

New Member
Hi,
I bought a defect Nikko Alpha 450 yesterday and will start to repair the unit soon. It powers up but there is no sound. Before further investigating I searched for a schematic or service manual but could not find it on the web. Does anyone have it or knows where I can get one?
Thanks
Jos
 
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If you don't get a copy from someone here, A.G. Tannenbaum has the service manual for the Alpha 440 available for $20.00. The Alpha 450 is supposed to be internally the same as the 440, only the front panel cosmetics are different. That's what the company told me when I bought my 450 back in the '80s. Be forewarned that you may find it it difficult to locate replacement driver and output transistors for the amp.

https://www.agtannenbaum.com/agtannenbaum.root/shop/showcart.aspx?task=view
 
I have a Nikko Alpha 440 awaiting repair, I'll be interested to read about your progress! Don't have the service manual, unfortunately, only the owner's manual. Mine was a great amp while it worked.
 
Thanks for the link Glen. I will order the manual.

Marantz, I will post progress as soon as I have the manual and start troubleshooting.
 
I have started to do some checking on the amp now. The driver and pre-driver transistors on one channel are all shorted and will need replacement. I removed them all including some burned resistors and am serching for replacements (indeed difficult to find Glen). I disconnected the power form the defective channel and powered on.
The relays click so thet looks ok. I will further check the power supply now and see if the remaining channel works.

Marantz, What is the problem with your Alpha? Maybe I can check something for you?
 
The PWS seems to be ok, I measure the following voltages:

On the Right regulator board (Right board when looking at it from the Amp Front)
Pin 5: +74.6 V
Pin 3: -73.2 V
On the connector going to the power amp:
Red Wire: +80V
Black Wire: 0V
Blue Wire: -80V

On the Left Regulator board (Left board when looking at it from the Amp Front)
On the connector going to the power amp:
Red Wire: +80V
Black Wire: 0V
Blue Wire: -80V

The connectors to the Power Amp are located between the large capacitors on the regulator boards.
 
Last edited:
Hi,

I’ll copy here a question I left in another thread because I believe it's clearly relevant!

If someone could tell what are the true specs for the Alpha 450. Actually a potential seller told me that it is a power amp, 220 watts in 8 ohm and 440 watts in 4 ohm. In another advise (on ebay if I remember) I’ve seen 220 in 8 ohm and 240 in 4 ohm.

Whatever the truth is, I’m very skeptical about those 440 watts in 4 ohm, and as I will drive 4 ohms speakers, I need to know. On the other hand, 26 kgs for this power amp inspire a certain respect and trust. So I’d like to know what wattage could deliver this amp in 4 ohm and generally speaking if it is able to drive difficult load speakers.

Thank you.
 
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