Amplifier Project – Part 2

Sourcing Parts

The part sourcing turned out to be more difficult than originally thought.  The concept of harvesting components turned out to be a bit optimistic, there were but a handful of parts that can be used, mostly to do with the power supply.

All the resistors, caps and transistors were purchased on eBay (from US based companies so I could get them in a reasonable amount of time).  The transformer that was removed from the Integra receiver will work for this project, but I was hoping to find something smaller.  But a 50VAC center tap transformer is somewhat hard to find, and of the few that were located, the price and shipping was beyond what I felt was acceptable.  So the existing transformer will be used.

Testing The Transformer

The transformer is marked P/N NPT-1281D, and also indicates that it’s an Onkyo part… so that solves the mystery of who Integra is.

The transformer was wired to AC using an old server power supply cable that was in the parts graveyard, soldered to the existing PCB.  A piece of cardboard was taped over the exposed connections so I didn’t inadvertently shock myself.

Measured all voltages with reference to the center tap.  It’s a little less than what’s called out for on the schematic, but it will have to do.

Transformer_2 Transformer_3
Since the parts for the amp are in transit, well, most are anyway, and I think there’s enough parts to build the power supply, I’ll get started on that next.




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