Ok... will end the night with a close up of the protection circuitry.
Again, the amp is working. But the voltages in this section are bizaro!
There is 48 volts across the relay so the output is connected 22uH inductor! My iTunes sounds fine!!
One thing about the transistor pairs, they are installed back-to-back. You can see from the images below, that the bases of T1 (right side) and T2 (left side) are connected (center traces). You can also see that the Emitter of T1 is connected to the Collector of T2 (bottom view image, bottom traces). There is nothing else connected there.
There is 2.0v on the bases of T1 and T2. The Emitter of T1 has .4v. So that transistor is not turned on, or is it? The Emitter of T2 is at 0V. In fact, that point is tied to Ground. I updated the schematic.
There is .6v on the bases of T3 and T4. The Emitter of T4 is at 0v. However, the Collector is at 0v (because the connected points go to Ground). The same scenario with T3. We have the proper Base to Emitter voltage but the Collector is at 0v - odd indeed.
I tried to be very careful tracing this out while I inserted the parts. I checked the continuity from point to point during assembly.
So this is a mystery!
Again, the amp is working. But the voltages in this section are bizaro!
There is 48 volts across the relay so the output is connected 22uH inductor! My iTunes sounds fine!!
One thing about the transistor pairs, they are installed back-to-back. You can see from the images below, that the bases of T1 (right side) and T2 (left side) are connected (center traces). You can also see that the Emitter of T1 is connected to the Collector of T2 (bottom view image, bottom traces). There is nothing else connected there.
There is 2.0v on the bases of T1 and T2. The Emitter of T1 has .4v. So that transistor is not turned on, or is it? The Emitter of T2 is at 0V. In fact, that point is tied to Ground. I updated the schematic.
There is .6v on the bases of T3 and T4. The Emitter of T4 is at 0v. However, the Collector is at 0v (because the connected points go to Ground). The same scenario with T3. We have the proper Base to Emitter voltage but the Collector is at 0v - odd indeed.
I tried to be very careful tracing this out while I inserted the parts. I checked the continuity from point to point during assembly.
So this is a mystery!
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