Nikko Alpha 230 amp

[salimchehab]

hi

I have a Nikko amplifier, it is stuck on protection mode. I just bought it
from someone who said that It is working, and It appears it is not, I opened the cover, all looks fine inside, no smell of any buring items or anything. When I start it, it light on, but the protect light stays red and I dont hear a sound. Can someome help, I live in NJ and I am looking for a tech who could fix it. THANKS

 

[timvreug]

I talked with Brian Donegan of twisted pear audio, and he sent me the schematic of the drivers. I attached them.
Most likely, from what I have learned this week working on a friends Amp, is that your main driver transistors have shorted. If you take the bottom cover off, in the middle on the big heatsink you will find 8 transistors, the forward set of four drive the left channel, the aft set of four drive the right channel. If you take a meter to the transistors, leg to leg you will find a dead short.
The reason you don't see any burnt up stuff is because of the over current protection. This is a professional amp, and you don't want a fire or smoke onstage. Anyways, it is really hard to find the original toshiba transistors, and most everything out there is fake, so good luck. The one I was working on had all the right channel blown out as well as the final stage of the preamp which railed the drivers and took the whole thing down. There may be more, but I killed the right channel by lifting out the dead components, and was able to get it working on the left only, so a minor victory.

Good Luck.