Another opinion: Looks like you have something open on the NPN output Q2L. 0.7 volts on the base and 0 on the emitter should be drawing plenty of current. Besides bad output, Check wiring (including collector connections which are through the screws going into the transistors case) and possibly loose or dirty connections on the socket that the transistor mounts into.
Hi Bob,
I can't see those numbers clearly. But in answer to your question, if you can adjust the voltage with the trimmer, it seems to be working. Can you send the two pictures of the schematic this way please? I have the schematic, but I need to see your measurements better.
Hi Ken,
You wandered fairly OT there. Let's get it working first. As far as the amp is concerned, it's a nice little amplifier, especially for the money. I used to own one in fact. I've also worked on far worse products. In the great scheme of things, that Nikko Alpha II isn't that bad.
Best, Chris
I can't see those numbers clearly. But in answer to your question, if you can adjust the voltage with the trimmer, it seems to be working. Can you send the two pictures of the schematic this way please? I have the schematic, but I need to see your measurements better.
Hi Ken,
You wandered fairly OT there. Let's get it working first. As far as the amp is concerned, it's a nice little amplifier, especially for the money. I used to own one in fact. I've also worked on far worse products. In the great scheme of things, that Nikko Alpha II isn't that bad.
Best, Chris
Steve, I recently pulled Q1 and Q2. Q2 socket and Q1 are on a small pcantyva@gmail.com will reflow emitter wire connection on board. I am thinking all the wire wraps on the amp board should be soldered? Wanted to get fresh compound between Q1 and the heatsink. Also cleaned off old compound on Q2 and replaced mic.a insulator with Silgard. Yes Q2 has 700mV from base to emitter...it should be conducting. Will poke around that area...the wire connections on think and look harder at those potential mechanical defects. Thanks for your thought
Chris, I remember after acquiring this amp noting that the thermal compound on several of the outputs appeared to have been allowed to heat up to a point allowing the compound to thin and run down the heatsink. Have you seen this before? I didn't know then that the transistors were in sockets so I wasn't too interested in unsoldering to clean up and make it right ensuring proper Thermal transfer. In this situation it must have been a bad connection on either the base or emmitter.
Steve, you hit the nail right on the head with your observation and comment concerning Q2. I initially confused Q2 with Q3. It is Q3 that is mounted to pcb with Bias transistor. This was the output that I had already removed and reinstalled. Removal and clean up of Q2 allowed proper idle current. Kudos Steve.
Hi Bob,
I have seen that from time to time. But it doesn't happen with overheating all the time. Most overheated parts convert the grease into a dry film. I think he had to cook the amp that had excessive grease around the part, and maybe the type of grease is more important. Overheating will tend to dry the grease out every time.
I couldn't find your diagram anywhere. Sorry I couldn't be more helpful.
-Chris
I have seen that from time to time. But it doesn't happen with overheating all the time. Most overheated parts convert the grease into a dry film. I think he had to cook the amp that had excessive grease around the part, and maybe the type of grease is more important. Overheating will tend to dry the grease out every time.
I couldn't find your diagram anywhere. Sorry I couldn't be more helpful.
-Chris
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