The Fisher 500C is a 75 watt receiver that uses four 7591 output tubes. It is a surprisingly good sounding unit, as is all the fisher gear from this era. The tuner is FM only (the 800C is identical to this unit, but also has AM). In it's stock form, it sounds quite good, but like all vintage gear, benefits from modern capacitors and resistors. If I had to build up a simple low cost system, this unit would be at the top of my list. It works remarkably well with the Quad ESL's. Like all gear from this era, it uses twist-lock can capacitors, which are now getting impossible to find. I have designed a capacitor board to replace the four can caps in this unit. The plans for this board can be downloaded below.
Fisher 500C schematic (508 K)
Fisher 500C Cap-Board (374 K)