LED Driver Cross-Reference: Replacing a Failed or Discontinued Unit

Replacing “like for like” on nameplate watts and volts is the single most common reason a replacement fails in the same way, in the same place, about 18 months later. The original unit did not die because it was unlucky. It died because of the ambient temperature, the load profile, or the dimming interface — and a replacement matched only on watts and volts inherits every one of those conditions.

Search behaviour confirms the pattern: buyers look up part numbers, not categories. A query like sdr250as24-f is someone holding a dead unit, reading the label, and needing the job back up. That person has already decided to buy. The only question is whether they find you.

Here is how to build the cross-reference properly.

The Six Parameters to Match

Two are obvious. Four are the ones that decide whether the replacement survives.

Step 1 — Read the Label, Then Measure

The label gives you nominal values. Measurement gives you the truth.

A Fluke 87V or any true-RMS meter covers the electrical readings; a Fluke TiS75+ thermal camera gives you the housing temperature in about 20 seconds and tells you more about why the old unit died than the label ever will.

Step 2 — Decode the Part Number

Most manufacturers encode wattage and voltage in the model string. Work the example:

Read it as 250 W, 24 V. Current follows from Ohm’s law:

Now you have three numbers to match — 24 V / 250 W / 10.4 A — and you can shop across brands.

Step 3 — Apply the Derating You Skipped Last Time

If the old unit died from heat, match the rating at the operating temperature, not at 25°C.

If the cavity measured 58°C and the old unit was a 250 W part, it was living as a 175 W unit. If your measured load is 190 W, the original was undersized from day one — and replacing it with another 250 W part repeats the failure. Go to 350 W, or fix the ventilation.

See 600W Switching Power Supply: Sizing, Derating and Cabinet Layout for 24V LED Walls for the cabinet-layout side of this.

Step 4 — Mapping to a Replacement

Using the 250 W / 24 V example, and knowing the mounting environment:

Say this plainly to the buyer: a cross-reference gives electrical and mechanical equivalence, not guaranteed pin-for-pin interchangeability. Always check terminal pitch, cable entry direction and mounting-hole centres against the cavity before ordering.

Step 5 — The Counter-Intuitive Check: Weight

If the replacement weighs half what the original weighed, that is a warning, not a win. Higher power density comes from smaller magnetics and smaller capacitors. Electrolytic capacitors are the first component to fail in a switching supply, and a physically smaller unit almost always means:

• Lower capacitor ripple-current rating
• Less thermal mass to ride through transient peaks
• Higher internal hotspot temperature

Compare the capacitor temperature and hour rating (105°C / 10,000 h is the target) before you accept a price that seems too good. A replacement that costs 30% less and lasts 40% as long is the more expensive option. The 11 QC gates article covers what to ask the factory about this.

Step 6 — Check What the Old Unit Was Actually Protecting Against

Four failure causes survive a naive replacement:

1. Thermal — fixed by upsizing or ventilating, not by swapping brands
2. Surge — if the site has poor mains, specify 4 kV differential / 6 kV common mode (IEC 61000-4-5) and ask about repetition tolerance
3. Moisture — if the old unit showed internal condensation, raise the IP rating or fix the cable gland and drip loop, not just the model
4. Overload — if the load grew after the original install (extra modules added), the original was never the problem

OLD UNIT
  Model string:        ____________   Decoded: ____ W / ____ V / ____ A
  Output type:         CV / CC
  Dimming:             none / 0-10V / PWM / DALI / TRIAC
  IP rating:           ____      IK rating: ____
  Dimensions L×W×H:    ____ × ____ × ____ mm
  Terminal pitch:      ____ mm     Cable entry direction: ____
  Certifications:      ____        File number: ____
SITE CONDITIONS
  Measured load:       ____ W
  Ambient at driver:   ____ °C   (measured, not forecast)
  Cavity depth:        ____ mm
  Water exposure:      none / splash / jet / pooling
  Mains quality:       good / surges observed / unknown

REQUIRED REPLACEMENT
  Voltage:             ____ V
  Power after derating: ____ W ÷ factor ____ = ____ W
  → Specify:           ____ W, IP____, dimming ____

Why This Page Exists

Part-number searches are small individually and add up collectively. Every discontinued model in your market, every dead unit in a service van, is a query with one intent and no comparison shopping. A page that teaches the matching method — and carries a table mapping common ratings to available units — ranks for dozens of these at once and converts at a rate category pages never will.

Send us the model string off the failed unit. We will decode it, confirm the six parameters against your site conditions, and tell you if the original was undersized. → Request a quote · Datasheets & certificates · IP67 series