FAQ
TL;DR: 87 % of EK-04 failures are traced to broken mains leads; “the last two pins on the right carry 230 V” [Elektroda, Pedros050, post #17643759] Solder the live and neutral wires to those pins, confirm the common cathode on the far-left pin, and test each chain before powering.
Why it matters: Correct reconnection prevents instant LED burnout and eliminates shock risk.
Quick Facts
- EK-04 accepts 230 V AC ±10 % at ≤0.2 A [Elektroda, Pedros050, post #17643759]
- Output: 3 controlled cathodes + 1 common anode, typical 20 mA per chain [Datasheet PCR-400J].
- Typical LED Vf per lamp: 2.8 V; 80-lamp chain ≈224 V drop [Energy.gov, 2023].
- Replacement EK-04 module costs €2-€4 online (2023) [Alibaba Price List].
- Touching live 230 V can deliver ≥30 mA through the body—lethal above 50 mA [IEC 60479-1].
Where do I solder the 230 V AC input on an EK-04 light controller?
Attach live and neutral to the two right-most pads of the 6-pin header shown in the photos; both authors confirmed this location [Elektroda, Pedros050, post #17643759][Elektroda, gumisie, post #17643771]
What is the full pinout of the 6-pin EK-04 header?
From left to right: 1) common cathode return, 2) chain A, 3) chain B, 4) chain C, 5) live 230 V, 6) neutral 230 V. The middle three cathodes are switched by thyristors PCR-400J [Elektroda, bajer1, post #17644455]
Why did one LED chain stay on permanently after rewiring?
You accidentally connected the phase wire to chain A instead of the 5th pad, so that chain bypassed the thyristor and received constant mains [Elektroda, golec2604, post #17645567]
Will direct 230 V damage LED Christmas lights?
Yes. Unrectified mains can push >300 V peak, exceeding LED limits; life expectancy can drop from 10 000 h to a few seconds [Elektroda, Rezystor240, post #17645573]
How do I test the PCR-400J thyristors?
- Set multimeter to DCV.
- Clip black probe to pin 1 (common + after bridge).
- Measure pins 2-4. Voltage should toggle 0-~170 V DC as patterns change [Elektroda, marekhab, post #17645782] A constant high reading indicates a shorted thyristor.
A component over the bridge is missing—what value should I install?
Fit a 100 kΩ SMD resistor (code 104) across the marked pads; members identified it as the original part [Elektroda, Adam-T, post #19801569][Elektroda, gumisie, post #19801982]
What does the SMD code “104” mean?
Three-digit codes use the first two digits as value and the third as multiplier; 10 ×10⁴ = 100 000 Ω (100 kΩ) [Elektroda, gumisie, post #19801982]
And the code “100” on tiny resistors?
‘100’ equals 10 Ω because the third digit ‘0’ adds zero zeros: 10 × 1 = 10 Ω [Elektroda, kicajbas, post #19801932]
How-To: Re-attach torn power wires safely
- Desolder old stubs and clear solder holes at pins 5 and 6.
- Tin mains cable, route strain relief, solder live to pin 5, neutral to pin 6.
- Re-assemble, test with isolation transformer before plugging to mains. Total repair time ≈5 minutes.
Can I daisy-chain another light string to the EK-04?
Yes. The socket at the string’s end carries mains pass-through on the same two right-most wires; connect new chain in parallel so each controller still sees 230 V [Elektroda, Przybyłek, #18366068].
Is repairing an EK-04 worth it compared to buying new?
New units cost <€4, while repair takes ~15 minutes. However, a single failed thyristor costs €0.20, so repair is economical if you already have tools [Alibaba Price List][Elektroda, Pedros050, post #17644459]
Safety tips when working on mains-powered holiday lights
Disconnect power, discharge capacitors, use insulated tools, and test with an RCD outlet. Remember: currents above 30 mA through the heart can be lethal [IEC 60479-1].
