39 V rail clamp or reference — what the DO-35 package tells you
The 1N6014B/TR is a 39 V Zener diode in a DO-35 glass axial package, rated for 500 mW continuous dissipation. The 39 V nominal (Vz) with ±5% tolerance means it holds the regulation band between roughly 37 V and 41 V — tight enough for a 36 V supply rail clamp or a 39 V shunt reference in a low-power bias supply. The DO-35 body is small and through-hole, so it inserts into a 0.025-inch hole on a standard PCB and reworks cleanly under a soldering iron — no hot-air station needed for removal or replacement. The glass seal holds up to the full -65°C to 175°C temperature range, making it usable in engine-bay or cold-environment gear.
Leakage and forward drop — the standby budget
Reverse leakage is specified at 100 nA maximum when biased at 30 V — that is 30 V below the nominal zener knee, so the diode draws negligible current when the rail is below the regulation threshold. In a battery-powered reference circuit this leakage is well below the self-discharge rate of most lithium cells. Forward voltage is 1.1 V maximum at 200 mA forward current. If the diode ever sees forward bias in a transient, the 1.1 V drop limits the voltage excursion across the junction, but the 500 mW power limit still governs — 200 mA forward at 1.1 V is 220 mW, within the rating.
Active production — sourcing reality
The tape-and-reel packaging (TR suffix) means it ships on a reel for automated insertion, not in bulk or cut tape. For a small prototype run the reel quantity may be more than needed, but the part is also available in other packaging options through the same supply chain.