FANUCA20B-1000-0770-01Control Power Supply Unit, Variant -01, for Legacy CNC Control Cage

Product Description

What this part is

A Fanuc A20B-1000-0770 power supply unit, variant -01 — the switching power supply that feeds the logic and control rails of a legacy Fanuc CNC / servo control cage. It converts the incoming AC supply into the regulated DC rails the master board, memory, axis and I/O cards need, and it is the part that fails most often in an old control, because electrolytic capacitors age whether the machine runs or not.

This is the control-side power supply, not a servo or spindle drive power section. Supplied as the power supply unit only.

Decoding the order code

A20B – Fanuc printed-circuit-board and board-level assembly prefix. Fanuc numbers this power supply as a board-level assembly rather than under the A02B control-unit prefix.1000 – the generation group. A20B-1000 and A16B-1000 numbers belong to Fanuc’s earlier CNC and digital-servo generation — the same era as the Series 0 controls and the A06B-6050 / 6057 / 6061 servo units.0770 – the specific unit within that generation.-01 – the build variant of that unit. On Fanuc power supplies the trailing two-digit number distinguishes builds with different rail or input configurations, so it is worth matching. It is a different marker from the /nnX edition suffix seen on Fanuc boards, which is only a revision level.

What these specs mean in practice

Match the full number including the -01. Fanuc power supplies of this era look near-identical between variants, mount in the same way and use the same connector families, but the rail set and input arrangement differ — and a power supply that comes up on the wrong rails takes logic boards with it. Read the label on the unit you are replacing rather than working from the machine’s nameplate.

Note the condition: this unit is tested, which on a legacy power supply is worth having. It is still sensible to check the output rails on the bench under load before you commit it to a control that has expensive boards in it.

What is not included

Power supply unit only. This listing does not include the control cage, backplane or card rack, the master PCB, memory, axis or I/O cards, the CRT or LCD display, the operator panel or MDI keyboard, servo or spindle amplifiers, the input transformer or line reactor, AC input cabling, DC output harnesses or ribbon cables, connector or terminal-block kits, fuses, the SRAM backup battery, mounting hardware, or any documentation. Fanuc cage power supplies are normally fed through a machine-specific harness; that harness is not supplied.

Quantity and configuration

Sold as 1 piece — one power supply unit. New old stock, in an opened box, tested.

Installation and setup notes

Isolate and lock out the machine, and allow the unit to bleed down before handling — the primary side and the bulk capacitors hold a dangerous charge after power-off. Photograph and label every input and output connector before removal; several of the plugs on this generation will physically cross-fit and produce an out-of-tolerance rail rather than a refusal to start. On first power-up, bring the supply up with the logic cards out, confirm each rail against the label, then fit the cards. If the unit has been in storage for years, expect to re-form the capacitors by bringing it up gently rather than at full line voltage from cold.

Interchange guidance

Searchable equivalents of the same part: A20B-1000-0770-01, A20B10000770-01, A20B-1000-0770, A20B10000770, A20B 1000 0770, A20B-1000-0770/05A. Different editions of the same number are the same unit at a different revision. Other trailing variants of A20B-1000-0770 are related builds, not equivalents — confirm the rail configuration before substituting one.