Thursday, January 05, 2012

Power amp time.

Up for consideration is a late 1970s Spectro Acoustics 202C amplifier. The internet reports a lineage to Phase Linear amplifiers.

Control set is rather sparse. Liberal use of fuses though, each internal channel PCB contains two more fuses. So. To recap: No power switch or volume control; one power cord, two RCA inputs, one 4 terminal barrier strip speaker output and seven fuses

Lean and to the point. Though, mismatched electrolytics on the positive and negative supply rails don't match up to the gut shot I've seen.

Hardly a huge concern, as it's clear these caps are beyond usable lifespan anyway.

While I fully support reuse, I'd feel better if the old insulation had been cleaned of the cut leads (or even, you know, removing the previous wiring completely during the preparation phase of the work).

The preceding lack of attention to details makes me wonder about this fix, including speculation on what sort of "parasitic" resistance the charred carbon path on the visible side of the PCB reflects.

Smoke signals are spelling out the recommendation to proceed with caution.

The Spectro Acoustics appear to be well regarded amplifiers though, so it may be worth the effort to get right.


krivx said...

What's the rated power? Doesn't look like the output transistors have much heatsinking...

crochambeau said...

100 watts a side. I agree, looks like it would run hot.