PLC Rack Dead? Check the Power Supply Before You Buy a CPU
A dark rack, a processor that faults when the panel warms up, or I/O that browns out intermittently — the rack power supply is the usual culprit, and it is dramatically cheaper to fix than the CPU everyone suspects first. Supplies repair beautifully: rectifiers, capacitors, and fans are all standard bench work.
What's usually behind it
Aged filter capacitors
The dominant failure in 10-30 year old rack supplies. Output sags under load, the rack faults when warm, then one day it doesn't come up at all.
Rectifier / input stage failure
Takes the supply out completely, sometimes with a popped fuse upstream. Board-level repair.
Fan failure and heat death
A seized fan cooks everything downstream. Fans are replaced as standard in our supply repairs.
It actually IS the CPU (rarely)
If the supply tests good on load, we tell you — and we're honest that most dead CPUs have no economic component-repair path. Test-and-verify beats false hope.
Repairs that fix this
Multi-brand
$349PLC Power Supply Repair
A dead rack is usually a dead power supply — and power supplies repair beautifully. Flat $349, load-tested before return.
3–5 business days in lab · Buy online now →
Multi-brand
Free evaluationPLC Module Repair
Failed I/O channels, dead comm modules, obsolete analog cards — free evaluation, typical repairs $250–$650. And we'll tell you straight when a module isn't worth repairing.
3–5 business days in lab · Free evaluation →
Machine down? Let's get it back up.
Start a repair online in two minutes, or send us the part number for a free technician review.
The Fixed-or-Free Guarantee: if we can't repair it, you don't pay for the repair.
Call (817) 799-7332 · 📱 Text us a photo of your unit · Email repairs@controlboardlab.com