EI-4120W-5409 Dual Voltage Power Transformer - 110 V / 220 V Input | 12 V-0-12 V and 24 V 250 mA Output | EI-41 Silicon Steel Core | Chassis Mount
EI-4120W-5409 is a chassis-mount dual voltage power transformer: two 110 V primaries for 110 V or 220 V mains, and a centre-tapped secondary giving 12 V-0-12 V or 24 V at 250 mA.
- Dual 110 V primary: 0-110 V on 1-2 and 0-110 V on 3-4, wired in parallel for 110 V or in series (1-4) for 220 V mains
- Centre-tapped secondary: 12 V-0-12 V on 5-7-8, or 0-24 V on 5-8, rated 250 mA
- EI-41 silicon steel core for high magnetic permeability and low eddy-current loss
- Eight 6.3 x 0.8 mm solder tabs at 11.5 mm pitch, 4 + 4, for direct chassis wiring
- Dual mounting flanges: 44.0 +/- 0.5 mm hole pitch, 4.5 x 6.5 mm holes
Built in a flame-retardant bobbin and sealed in a metal cover carrying the full terminal configuration on its nameplate. Total width including flanges 53.5 mm MAX, total height 36.0 mm MAX, body 34.5 +/- 0.3 mm along the terminal row.
1. Product Name
EI-4120W-5409 Dual Voltage Power Transformer, chassis mount, EI-41 silicon steel core, 110 V / 220 V dual primary, 12 V-0-12 V and 24 V 250 mA secondary, 8 solder tabs.
The part is built around an EI-41 lamination in a flame-retardant bobbin, enclosed by a drawn metal cover with two integral mounting flanges. The nameplate on the cover states the model and every terminal function, so the wiring can be read directly off the component.
| Item | Specification |
|---|---|
| Model | EI-4120W-5409 |
| Product type | Chassis-mount dual voltage power transformer |
| Input | 0-110 V (1-2) + 0-110 V (3-4) dual primary; 0-220 V (1-4) when series connected |
| Output | 12 V-0-12 V / 250 mA (5-7-8) or 0-24 V / 250 mA (5-8) |
| Core | EI-41 silicon steel lamination |
| Termination | 8 solder tabs, 6.3 x 0.8 mm, 4 + 4 |
| Mounting | Two flanges, 44.0 mm hole pitch, 4.5 x 6.5 mm holes |
| Package | Metal cover, chassis mount |
2. Feature
Dual voltage primary — Two 110 V windings, wired in parallel for 110 V or in series for 220 V mains (0-220 V on 1-4).
Centre-tapped secondary — 12 V-0-12 V on terminals 5-7-8, or 24 V on terminals 5-8, rated 250 mA.
EI-41 silicon steel core — High magnetic permeability and low eddy-current loss.
Eight solder tabs — 6.3 x 0.8 mm lugs arranged 4 + 4, for easy wire soldering and chassis connection.
Dual mounting flanges — 44.0 mm hole pitch with 4.5 x 6.5 mm holes for secure chassis installation.
Flame-retardant bobbin — High temperature resistance and enhanced safety.
Metal cover — Sealed construction with a printed nameplate showing the winding configuration.
High isolation — Separate primary and secondary windings for circuit isolation.
3. Advantage
One part, two mains voltages — The dual primary covers 110 V and 220 V markets from a single part number.
Two output configurations — The centre-tapped secondary provides 12 V-0-12 V or 24 V without a second part.
Low distortion — Silicon steel lamination and a stable winding structure keep waveform distortion low.
Thermal stability — Flame-retardant bobbin and a metal cover support high temperature resistance in continuous use.
Stable performance — Consistent electrical behaviour unit to unit for series production.
Serviceable connection — Solder tabs allow field re-termination and chassis wiring without a PCB.
| Terminals | Function |
|---|---|
| 1-2 | Primary 1 — 0-110 V winding |
| 3-4 | Primary 2 — 0-110 V winding |
| 1-4 | 0-220 V when the two primaries are connected in series |
| 5-7-8 | 12 V-0-12 V centre-tapped secondary, 250 mA |
| 5-8 | 0-24 V secondary, 250 mA |
4. Application
Audio equipment power supply — Mains step-down feeding the analogue and digital rails of audio equipment.
DAC and preamplifier builds — Transformer supply in reference DAC and preamplifier chassis.
Power supply filter boards — Board-level supply in equipment with a separate filter stage.
General chassis-mount equipment — Any 110 V / 220 V application requiring an isolated 12 V or 24 V rail at 250 mA.
The transformer is mounted to the chassis and wired to the board with flying leads, so the primary and secondary circuits are isolated from one another and the safety earth is carried by the chassis rather than the signal ground.
5. Application Specifications
| Dimension | Value |
|---|---|
| Total width, incl. mounting flanges | 53.5 mm MAX |
| Hole pitch, mounting flanges | 44.0 ± 0.5 mm |
| Body depth, top view | 32.0 ± 0.5 mm |
| Body width, top view | 28.0 ± 0.3 mm |
| Mounting hole | 4.5 x 6.5 mm |
| Total height, front view | 36.0 mm MAX |
| Core and bobbin height | 32.0 ± 0.5 mm |
| Body length, terminal row | 34.5 ± 0.3 mm |
| Terminal pitch | 11.5 mm |
| Solder tab size | 6.3 x 0.8 mm |
All dimensions in millimetres, standard chassis mounting.
Electrical specification as printed on the nameplate:
| Parameter | Value |
|---|---|
| Input 1 | 0-110 V — terminals 1-2 |
| Input 2 | 0-110 V — terminals 3-4 |
| Input, series | 0-220 V — terminals 1-4 |
| Output 1 | 12 V-0-12 V / 250 mA — terminals 5-7-8 |
| Output 2 | 0-24 V / 250 mA — terminals 5-8 |
| Terminal | Position on the bottom view |
|---|---|
| 1 | Primary 1 start (0 V) |
| 2 | Primary 1 finish (110 V) |
| 3 | Primary 2 start (0 V) |
| 4 | Primary 2 finish (110 V) |
| 5 | Secondary start (0 V) |
| 6 | Secondary — centre tap return |
| 7 | Secondary centre tap (12 V-0-12 V) |
| 8 | Secondary finish (24 V) |
6. Quality & Testing Assurance
Verification — Rigorous performance verification on the audio R&D and quality testing workbench.
Dual-voltage testing — Each unit is checked on both the 110 V and 220 V primary connections.
Load stability — Continuous load stability check at the rated 250 mA output.
Compliance — CCC, CE, RoHS and UL markings are carried on the product artwork.