Nikko Alpha 650...caution, nudes inside.

[Rob41]

Wow! I felt a little skittish about spending $405 on an amplifier stuck in protection mode but I feel much better now.

This amp is beyond huge/robust etc. and the twin torroidial transformers look amazing inside the chassis.

While plugged in, I pressed each of the two 8A resets one at a time and on the second one, it popped the breaker in my house. Well I guess I can start looking at whatever channel that reset is for so at least I've got some idea where to start looking.

Did I mention how huge this thing really is in person? Lol

 

[JBL GUY]

Looks very nice!

I like the meters!

What is your impression of the sound quality?

 

[toxcrusadr]

Looks very nice!

I like the meters!

What is your impression of the sound quality?

Um, apparently the only sound so far is the tripping of the breaker in the house. Question might be just a tad premature.

 

[Rob41]

Looks very nice!

I like the meters!

What is your impression of the sound quality?

The silence is so quiet it's deafening! Lol

As soon as I repair it I'll cover the repairs and review the sound quality.

 

[vintageboy]

wow it is huge and I bet it sounds great by looking at it

 

[mech986]

Nice acquisition. Looks like 3 or all 4 of your power supply caps are bulging upwards, at least from the picture angle. Have any experience with this type of repair?

 

[Rob41]

Yeah, it's going to get all of the electrolytics replaced before I put it into service. This amp is too special to me to cut any corners.

 

[whoaru99]

Nice acquisition. Looks like 3 or all 4 of your power supply caps are bulging upwards, at least from the picture angle. Have any experience with this type of repair?

Maybe, but it's also not uncommon for the plastic cover disk to warp/bow.

I've looked in a couple amps and preamps and though the same but the plastic pushed down easily, there was no bulging underneath.

 

[Rob41]

Maybe, but it's also not uncommon for the plastic cover disk to warp/bow.

I've looked in a couple amps and preamps and though the same but the plastic pushed down easily, there was no bulging underneath.

The plastic tops of the caps do push down easily without any resistance.

Edit: I've been looking through the database here and on the internet and ebay and can't find a service manual or shematics or anything on the Alpha 650. If anybody has any of this information I would be forever grateful if I could get it/buy it from you. Thanks.

 

[guiller]

As soon as I repair it I'll cover the repairs and review the sound quality.

Please, do so. It looks awesome!

PS: here there are some specs of this beast: http://www.dnaelectronics.ca/specs/nikko_alpha_650.html

 

[Elliot Thompson]

Um, apparently the only sound so far is the tripping of the breaker in the house. Question might be just a tad premature.

Then something is definitely wrong with it.

The Alpha 650 will perform fine on a 15-A breaker. The power consumption is typical as many 250-watt per channel amplifiers designed in the late 70's - mid 80's.

Best Regards,

 

[whoaru99]

Well, OP's original post does say the amp was purchased knowing the protection light is illuminated.

 

[Elliot Thompson]

Well, OP's original post does say the amp was purchased knowing the protection light is illuminated.

Even in Protect Mode the amplifier shouldn't do that. He may need to examine the power supply.

Best Regards,

 

[Rob41]

Even in Protect Mode the amplifier shouldn't do that. He may need to examine the power supply.

Best Regards,

It could be any number of things, including a shorted out output transistor. The two resets on the back are 8 amps each and one is for the left channel while the other is for the left channel. The problem likely lies in one channel; the one that is tripping the house breaker.

 

[FootFungus]

This looks extremely similar to the Alpha VI from the top and bottom shots I've seen. The service manual for the VI is available online freely. Most likely the circuit will be very similar, just with later semiconductors.

BTW, what output transistors are used? They look like Sankens from here....

Also, check the big resistor behind the front left of the face plate. That is for the inrush limiter. Make sure its not measuring open.

And yes, yank the outputs and make sure they aren't short.

 

[whoaru99]

It could be any number of things, including a shorted out output transistor. The two resets on the back are 8 amps each and one is for the left channel while the other is for the left channel. The problem likely lies in one channel; the one that is tripping the house breaker.

What is your home power circuit breaker size and type.

I do find it interesting that closing an 8A breaker would trip what I'm assuming to be a larger one in the house panel while allowing itself to remain closed? Of course, not all breakers have the same trip characteristics but, still, seems somewhat odd.

 

[Rob41]

This looks extremely similar to the Alpha VI from the top and bottom shots I've seen. The service manual for the VI is available online freely. Most likely the circuit will be very similar, just with later semiconductors.

BTW, what output transistors are used? They look like Sankens from here....

Also, check the big resistor behind the front left of the face plate. That is for the inrush limiter. Make sure its not measuring open.

And yes, yank the outputs and make sure they aren't short.

Thanks for the information FootFungus, I will check all that you mentioned. You are correct about the Sankens. One bank has 8 2SA1117's which seem like they are easy to get while the other bank of 8 has the 2SC2608's which look like they might be harder to find.

@whoaru99, the two 8A resets on the back have a spring loaded feel to them so I may have been completing the ground while pushing on it even though internally it may have tripped instantly. So that may account for the 15A house breaker tripping.

 

[sregor]

What is your home power circuit breaker size and type.

I do find it interesting that closing an 8A breaker would trip what I'm assuming to be a larger one in the house panel while allowing itself to remain closed? Of course, not all breakers have the same trip characteristics but, still, seems somewhat odd.

Depends on what else is on the breaker - ask anyone who runs a toaster and a microwave at the same time. My guess would be shorted output transistors on that side - reset the breaker and a race between the house breaker and the 8 amp breaker, so depends on how much the other side draws and what else is on the circuit. Also, the house breaker might be "warmer" as their already is current going through it, so may trip quicker. Just my 2 cents.

 

[Rob41]

That's a real good point sregor. My main audio systen was on and two alienware laptops with very large AC adapters were on the same circuit at the time.

 

[whoaru99]

Depends on what else is on the breaker - ask anyone who runs a toaster and a microwave at the same time. My guess would be shorted output transistors on that side - reset the breaker and a race between the house breaker and the 8 amp breaker, so depends on how much the other side draws and what else is on the circuit. Also, the house breaker might be "warmer" as their already is current going through it, so may trip quicker. Just my 2 cents.

That's a real good point sregor. My main audio systen was on and two alienware laptops with very large AC adapters were on the same circuit at the time.

Yeah, a valid point but, still, two laptops and another stereo (unless maybe a big-ass Class A amp therein) shouldn't be pulling too much current. Of course, to the point, perhaps there's even more stuff on that circuit as well.