Product Overview
TO-3 Silicone Insulator Pads - Dry Mount, No Grease Required - 10 Pieces
Condition
Unused NOS. Bulk pack of 10 silicone insulator pads, sourced from a government research facility. Light blue flexible silicone construction with two large mounting holes and two small center pin holes, matching the standard TO-3 footprint. Minor surface scuffs visible on some units; no damage to function. Covered by our no-hassle guarantee.
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Product Overview
Ten TO-3 silicone insulator pads for dry-mount transistor installation. Each pad is precision-cut to the standard TO-3 (TO-204) metal-can footprint and made from thermally conductive silicone elastomer. They sit between the transistor case and the heatsink or chassis, providing electrical isolation while allowing heat to transfer - no thermal grease required.
Key Features
- Package compatibility: TO-3 (TO-204) metal-can footprint
- Material: thermally conductive silicone elastomer
- Dry installation - no thermal grease or compound required
- Hole configuration: two large outer mounting holes, two small offset center pin holes
- Approximately 45mm wide, light blue flexible construction
- 10 pads per pack
- Incompatible with TO-220, TO-247, TO-3P, and TO-264 footprints
Applications
- Restoring vintage solid-state power amplifiers and stereo receivers (Marantz, Pioneer, McIntosh) - place the pad on the heatsink, seat the replacement TO-3 transistor, and verify electrical isolation with a multimeter before powering up
- Replacing dried-out mica washers during a full transistor swap on a classic guitar amp or high-current audio output stage
- Mounting TO-3 voltage regulators or pass transistors to chassis in linear bench power supply builds - eliminates the grease mess and the annual re-torque that grease joints eventually need
- Industrial motor controller repair where the TO-3 collector tab carries live voltage and must be kept off the grounded chassis
- Hobbyist and maker projects using salvaged TO-3 devices - 2N3055, MJ15003, or similar - where you need isolation pads but do not want to buy a full industrial reel
Frequently Asked Questions
Do these require thermal grease?
No. These are designed for dry installation. The silicone elastomer transfers heat to the heatsink without compound on either face.
Do the mounting screws also need insulation?
Yes. The pads isolate the transistor body but not the mounting screws. Non-conductive shoulder washers or bushings on the screws are required to prevent the screw shanks from bridging the transistor case to the heatsink electrically.
What transistor packages are compatible?
These fit the standard TO-3 (TO-204) metal-can footprint only. They are not compatible with TO-220, TO-247, TO-3P, or TO-264 packages, which have different shapes, dimensions, and hole patterns.
Is the heatsink surface condition important?
Yes. The silicone material is flexible but puncture-sensitive. Burrs, metal shavings, or rough gouges on the heatsink surface can pierce the pad under screw pressure and cause an electrical short. Dress the heatsink surface before installing.
What is in the pack?
10 silicone insulator pads. No mounting hardware, screws, or shoulder washers included.
The TO-3 can is old tech that still pulls serious current - and a good insulator pad is the quiet part that keeps everything honest. Ten in a pack means you can do the whole output stage and still have a few left over for the next amp on the bench.
