Paperclip PSU Test Guide | Generated by AI

Home 2026.07

Question: How do I use the paperclip method to test whether my Great Wall (长城) 85W power supply is functioning, and how does the pin-4/pin-5 procedure work?

Answer:

The pinout note you pasted is describing the standard ATX PS_ON# jumper test — the trick works because on any ATX-spec 24-pin connector, shorting the green wire (PS_ON#, pulled to 5V internally) to a black wire (COM/ground) tells the PSU’s control IC “motherboard says start up,” bypassing the need for an actual motherboard.

Why pin 4/5 works (electrically):

The 24-pin connector has two rows of 12 pins. If you orient the connector with the plastic retention clip facing up and count left-to-right along the top row, PS_ON# and an adjacent ground land on positions 4 and 5. This is the same physical wire as “pin 16 → pin 17” in guides that count all 24 pins sequentially instead of by row — all of the 24 pin cables have the same pinout, even if the wires are not color-coded, so starting on the left side with the clip up and counting 4 pins to the right gets you there. Different vendors just document the count differently (sequential 1–24 vs row-relative). Your pasted instructions and the English-language guides describe the identical two pins.

Procedure (clean version):

1. Power off PSU, unplug from wall.
2. Disconnect every cable except the 24-pin main connector (and AC cable stays unplugged).
3. Orient 24-pin connector: latch/clip facing UP, pins facing you.
4. Count 4th and 5th pin, top row, left to right.
5. Bend a paperclip into a U-shape (strip any coating), insert both ends
   into pin 4 and pin 5 to bridge them.
6. Plug AC cable back in, flip PSU switch to "I" / ON.
7. Fan spins -> PSU can produce power and its self-protection/control IC works.
   Fan silent -> PSU is dead, or in zero-RPM idle mode with no load.

Important caveat for your case: a genuine ATX 24-pin connector is used on PSUs rated ~300W and up (that’s what a full ATX motherboard needs). An 85W “Great Wall” (长城) unit is almost certainly not a standard desktop ATX PSU with a 24-pin connector — 85W is in the range of:

Before doing the paperclip test, check:

# quick sanity check — does the label say "24-pin ATX", "Flex-ATX", or something proprietary?
# look for: model number printed on the PSU casing, then search datasheet

If your unit really does have a 24-pin main connector, the procedure above applies unchanged — the ATX spec is fixed regardless of wattage. If it’s a proprietary DC brick instead, the paperclip trick doesn’t apply at all; in that case, the actual test is a multimeter across output pins:

Expected rails (if standard ATX pinout is present):
+3.3V (orange), +5V (red), +12V (yellow), -12V (blue, legacy),
+5VSB (purple, always live even when PSU is "off"),
PS_ON# (green, ~5V floating, 0V when triggered),
COM (black, ground reference for all measurements)

multimeter test:
- Black probe -> any black/COM pin
- Red probe -> the rail you're checking
- Before jumper: PS_ON# should read ~+5V, all main rails ~0V
- After jumper (PSU "on"): PS_ON# should drop near 0V,
  +5V/+12V/+3.3V should be within ~5% of nominal, +5VSB always ~5V

If you can tell me the exact model number printed on the Great Wall unit (or share a photo), I can confirm whether it’s ATX-pinout-compatible or a proprietary brick, and give you exact pin assignments instead of the generic spec.

References:

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