Laser Power Supply for Legacy GPI and Verifire: Replacement FAQ
By Zygo | Published: 2026-11-01
Category: Tips & Care
Diagnose laser power supply faults on legacy GPI and Verifire systems, decide when a replacement is the right fix, and learn what to check before ordering.
Quick answer
If your legacy GPI or Verifire laser no longer starts, trips its supply, or drops output after warm-up, first rule out cabling and input power. When those check out, replace the laser power supply with the Zygo spare part 6500-0136-01 rather than attempting a repair.
Why the supply is the usual suspect on aging systems
Legacy GPI and Verifire interferometers are now well past their original service life, and the laser power supply carries the highest continuous electrical stress of any module in the laser assembly. Electrolytic capacitors and regulation components age faster than the optical head, so a supply that worked reliably for years can begin to sag under load or fail to strike the laser at all.
That failure pattern matters because the symptoms often look like a laser problem. A dim or absent beam, intermittent output, or a system that shuts down mid-measurement can all trace back to the supply rather than the laser tube itself. Before you condemn an expensive laser assembly, confirm whether the supply is delivering stable voltage and current.
When replacement is not the answer
Not every no-start condition justifies a new supply. Loose interlock connections, a tripped facility breaker, damaged umbilical cables, or a failed cooling fan can mimic supply failure. If the supply shows no visible damage and the system responds to a known-good cable or outlet, investigate those paths first.
Also consider whether the rest of the system is worth repairing. If the interferometer has other known failures or is being retired, a new power supply may not be the best use of budget. The diagnosis below marks the point to stop and reassess.
Symptom-to-action diagnosis
- Laser does not strike at all: Listen and look for the supply's startup click or indicator. Verify facility power at the outlet, inspect the supply fuse if accessible, and reseat the laser cable at both ends. If the supply remains silent with confirmed input power, the supply has likely failed. Silence with confirmed input power points to the supply, not the laser head.
- Output drops or cuts out after warm-up: Run the system from cold and note how long it takes to fail. If the beam fades or the supply trips consistently after a few minutes, thermal drift in the supply is the likely cause. Check that the supply's cooling path is clear, then replace the supply if the pattern repeats. Repeatable warm-up failure is a supply symptom; a one-off glitch is not.
- Supply trips the breaker or shows visible damage: Do not power the system again. A supply that trips a breaker, smells burnt, or shows bulged capacitors or scorch marks has failed internally. Replace it with part 6500-0136-01 rather than attempting a bench repair. Visible damage or repeated breaker trips ends diagnosis and starts replacement.
- Supply looks healthy but the laser still misbehaves: If input power, cabling, and cooling are all confirmed and the supply shows no fault, the problem may lie in the laser head or another module. Stop replacing parts by guesswork and contact Zygo support for a system-level diagnosis. When the supply checks out, stop and escalate rather than ordering another part.
Replacement part facts
- Laser Power Supply for Legacy GPI and Verifire: Zygo spare part 6500-0136-01 is a laser power supply for legacy GPI and Verifire systems, associated with the laser assembly. It is the direct-fit replacement for the supply in those systems, so you avoid adapting a generic supply to a legacy laser.
Laser Power Supply for Legacy GPI and Verifire
