Zener voltage and what it means for the rail
The 1N6007B is a 20 V Zener diode with ±5% tolerance — the regulation window sits between 19 V and 21 V. For a 24 V rail feeding a 20 V clamp, this is the knee where the diode starts conducting; below 19 V the leakage stays under 100 nA at 15 V reverse bias, so it won't load the supply in standby.
Power and temperature envelope
Rated for 500 mW continuous dissipation in a DO-35 axial-lead package. The -65°C to +175°C operating range covers military and industrial thermal profiles — a 20 V Zener in a 125°C ambient still has margin to the junction limit as long as the lead temperature is managed.
Obsolete — sourcing reality
Microchip lists the 1N6007B as obsolete. Sourcing goes through independent surplus channels — quantities are lot-specific and confirmed at RFQ. The DO-35 footprint is standard, so a parametric replacement from the same voltage class is a board-compatible swap if the BOM allows a different Zener family.