Uncle Josh's NOS Garage

Manufacturer

KOA Speer Electronics

1 part listed

KOA Speer Electronics is a resistor company in Bradford, Pennsylvania, and its name is the record of how it came about. Speer Carbon Company was a Bradford firm working in carbon and graphite, and among other things it made carbon resistors. KOA Corporation, founded in 1940 in Ina, in the Nagano mountains of Japan, was building a similar business on the other side of the world. In 1980 the two came together, KOA taking on the Bradford resistor operation, and the combined name stayed on the building. The plant is still there and still making resistors, which is not something you can say about many American passive component sites.

What they are known for. Resistors, in bulk and in variety. Thick film chip resistors are the volume business now, along with current sensing shunts, resistor networks, thermistors and fuses. The older axial leaded lines are what turn up as old stock: carbon film in the familiar small beige body, metal film for tighter tolerance work, and metal oxide and wirewound where the power rating matters. The CF series quarter watt carbon film parts on this page are the ordinary end of that range, the resistor that went into everything, sold by the reel.

Why the Japanese connection matters to a buyer. KOA came out of the same manufacturing culture that produced the tight process control Japanese passive makers were known for through the 1970s and 1980s, and the axial parts show it. Values sit close to nominal, the printing is legible, and the tape and reel packaging is consistent enough that a sealed reel is genuinely a known quantity rather than a hopeful one.

What this means for old stock. Carbon film does not change on a dry shelf. Its two enemies are moisture, which creeps past the lacquer coating over long humid storage and pushes the value up, and heat in service, which drifts it up permanently. Neither applies to a sealed reel kept indoors. That is the reason we buy sealed lots of carbon film and will not resell a loose handful that arrived with no packaging and no history: with this family the packaging is most of the evidence.

Questions about KOA Speer Electronics

What does CF1/4 mean?

CF is the carbon film family and 1/4 is the power rating in watts. The resistance value is not in the part number at all, it is on the colour bands, which is normal for a high volume axial line. We put the measured or banded value in the product name so that a search for the resistance finds the part.

Is KOA Speer an American or a Japanese company?

Both, by construction. Speer Carbon was a Bradford, Pennsylvania company and KOA Corporation is a Japanese one, founded in Ina, Nagano in 1940. They combined in 1980 and the resulting operation kept the Bradford site and both names. Resistors are still made there.

Does carbon film drift with age?

On a dry shelf, no. In humid storage over decades, moisture works past the lacquer coating and the value creeps upward by a few percent. In service, heat drifts it up permanently. Sealed factory packaging protects against the first and the second is a circuit design question. This is why we buy sealed lots and grade loose carbon film differently.

Why are these sold by the reel rather than by the piece?

Because opening a sealed reel is a one way change. It turns a sealed lot into open stock, it exposes the parts to whatever your storage is, and it cannot be undone. Lots are priced as lots for that reason. If you want a smaller quantity, ask, and we will tell you whether there is an open lot of the same part number on the shelf.

Should I use carbon film or metal film?

Metal film if you care about tolerance, temperature coefficient or noise, carbon film for everything else. The practical differences are that metal film holds a tighter value over temperature and generates less excess noise under DC bias. For a pull up, a bias network or a bleeder, carbon film is the right part and the cheaper one.