Product Overview
Motorola 330k Ohm Carbon Comp Resistor File Card - 10-Pack, 1/2W 10%, Unused NOS
Condition
Unused NOS. Ten resistors mounted on the original Motorola file card. Brown axial-lead bodies with Orange-Orange-Yellow-Silver band configuration. Markings legible on card tab: value, tolerance, and wattage stamped clearly. Sourced from an electronics distributor consolidating inventory.
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Product Overview
Motorola 6-185B81 - a file card of 10 unused carbon composition resistors, 330k Ohm, 1/2W, 10% tolerance. The card retains the classic Motorola Communications format: RETMA color code chart on the left panel, printed in U.S.A., with all 10 resistors mounted on card rails. This is the kind of period-correct part that restorers of vintage radios, tube amplifiers, and classic electronics look for when they need the real thing rather than a modern substitute.
Key Features
- Resistance: 330k Ohm
- Power rating: 1/2W (0.5W)
- Tolerance: 10%
- Type: Carbon composition
- Quantity: 10 resistors per file card
- Color code: Orange-Orange-Yellow-Silver
- Format: Original Motorola file card with RETMA color code chart
- Condition: Unused NOS - all 10 resistors present on card
Applications
- Desoldering a drifted or failed carbon comp from a vintage radio chassis and dropping in a period-correct Motorola replacement to keep the circuit original
- Tube amplifier restoration where the builder wants carbon composition character rather than the cleaner profile of a modern metal film resistor
- Boutique amp builds where the designer is deliberately specifying carbon comp for the noise and feel associated with older circuits
- Stocking a component bin for ongoing vintage electronics repair - a full card of 10 means the next job is already covered
- Collectors adding a complete, unmounted NOS Motorola file card to a vintage components collection
Frequently Asked Questions
Are these carbon composition or carbon film resistors?
Carbon composition. The research notes confirm carbon composition type, consistent with Motorola's standard production for this era and card format.
Is the 10% tolerance acceptable for vintage audio restoration work?
For most vintage radio and tube amplifier circuits, yes. Original equipment was designed and built around 10% carbon composition resistors, so a period-correct replacement at 10% matches what the circuit was engineered for. For high-precision or low-noise modern applications, a metal film resistor with tighter tolerance would be the better choice.
Should these be used as power tube screen resistors in an amplifier?
No. Carbon composition resistors should not be used as power tube screen resistors. If a power tube shorts, a carbon comp in that position can catch fire. Use a wirewound or metal oxide resistor rated for that duty instead.
Are all 10 resistors present on the card?
Yes. The card has all 10 resistors mounted and unused.
Motorola printed the RETMA color code chart right on the card - because in 1960-something, that was just good engineering. Somewhere out there is a vintage chassis waiting on exactly this value. Now it does not have to wait.
