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• The DPS-800GB/GN shuts itself down because it never receives the “ PSKILL / INHIBIT ” and “ PS_ON ” logic-low signals that the server backplane normally provides.
• Permanently tie both of those control pins to a local ground pin on the edge connector (and, for full-power operation, connect the “+12 V remote-sense” pin to the main +12 V blade).
• After these three jumpers are fitted the supply will start immediately and remain on; the 30 s time-out disappears.
Key points
Why the PSU turns off
• The DPS-800 family contains an MCU that boots on the 12 V-SB rail. If, within ≈25–35 s, it does not see PSKILL# low (presence latch) while PS_ON# is asserted, it commands an orderly shutdown.
• This prevents the unit from running outside an HP backplane and guards against unlatching inrush or fan faults.
Control-pin functions (HP literature and HP spare-board reverse-engineering)
Viewed into the card-edge, component side up,
pin 30 – +12V_SENSE(+) (must be tied to +12 V for full rating)
pin 31 – PS_ON# (active low, enables main converter)
pin 32 – +12V_SENSE(–) / NC (varies by revision)
pin 33 – +12VSB (≈0.3 A) (always present)
pin 34 – Logic Ground
pin 35 – PRESENT# / SDA (I²C) (ignore for bench use)
pin 36 – PSKILL# / INHIBIT# (active low; watchdog reset)
pin 37 – SCL (I²C) (leave open)
pin 38 – Power_Good (open-collector) (optional monitoring)Revisions A/B vs. GN: some manuals number from the opposite end; therefore many hobbyist guides quote “short 31-34” (same nodes as 33-36 if counted the other way). Match pins by signal name, not number.
Minimum wiring needed for stand-alone operation
• GND can be any return blade or pin 34.
• Permanent strap: PSKILL# → GND.
• User switch (optional): PS_ON# → GND through a toggle so you can turn the 12 V rail on/off.
• Sense: pin 30 (+12 sense) → +12 V power blade (short piece of 18-22 AWG). Without this, the unit regulates a few hundred millivolts high and may drift.
• No other pins need attention; I²C, PGOOD etc. can float.
What happens if only PS_ON# is grounded
The main 12 V comes up, PGOOD asserts, but after ≈30 s the firmware sees PSKILL# still high and removes drive. That is exactly the symptom the question describes.
If it still shuts down after correct jumpering
a) Verify the +12 VSB (~12.1 V) is present whenever AC is applied.
b) Inspect/replace the two 47 µF – 100 µF 35 V electrolytics in the standby fly-back and bootstrap circuits (high-ESR parts cause the MCU to brown-out).
c) Check fan tach lead: on some GN units the MCU kills the supply if the fan is not spinning or tach pulses are missing. Make sure the native fan is connected, or emulate ~1–2 kHz tach with a 555/open-collector driver if you have replaced the fan.
d) Check for over-current: bench supplies should have at least a small load (5–10 W, e.g. a 12 Ω/25 W resistor) to keep the current-mode loop stable at power-up.
• Re-purposing server PSUs for LED lighting, crypto-miners and RC battery chargers remains popular because of their high efficiency (>90 %) and low cost.
• Community documentation (RCGroups 2023 threads, elektroda 2022 posts) confirms the same three-wire mod for the latest GN revision.
• Some users replace fans with quieter 40 mm models plus a PWM spoof board; an open-source microcontroller project (2024, on GitHub “ServerPSU-Fan-Quiet”) injects a valid tach and PWM so firmware keeps running while noise is reduced.
• Timer logic: the DPS-800 MCU reads an opto-isolated PSKILL# line pulled up to +3.3 V inside. When low for >5 ms it sets a present_ok flag and clears a watchdog counter; if the counter reaches ~1800 ticks (≈30 s) without reset the firmware toggles PG_OFF → shut-down.
• Remote sense: the regulator compares the sensed pins to an internal 12.00 V reference. Leaving sense open makes the PSU think the voltage is low, so it adds about +0.25 V headroom; this is within spec but can upset tightly-rated loads (FPGA dev boards, chargers).
• Fan default: in the absence of host PWM, firmware drives 100 % duty cycle. Noise ≈ 52 dBA. You can insert a 25 kΩ resistor from FAN_PWM to 12 V to force 40 % duty cycle; make sure airflow is still > 9 CFM at full load.
• These PSUs are safety-approved components only when used inside the HP metal chassis. Modifying wiring voids approvals (UL, CE). If you sell a project that incorporates a modified PSU you become the manufacturer and must ensure compliance with IEC 62368-1.
• High-current 12 V rails (>65 A) are a burn and fire hazard. Provide proper bus bars, fusing, and insulated enclosures.
Implementation checklist:
Potential challenges and mitigation
• Mis-counting pins – always cross-check with continuity meter to identify ground blades.
• Over-voltage due to open sense – verify link with ohmmeter.
• Fan connector polarity – use the native fan or replicate tach pulses.
• Some late-production GN units have a secondary watchdog on the serial/I²C bus; if it sees SCL/SDA permanently high it still runs. If HP firmware ≥3.2 is loaded and the PSU continues to time-out, cut trace TP113 (I²C present detect) shown in service schemas.
• Capacitor ageing: units above 7 years old often require replacement of all secondary 330 µF/16 V low-ESR caps to restore full 62 A rating.
• Explore the open-source “DPS-800GB digital interface” project (GitHub 2024) that exposes the PMBus registers; you can read live current, temperature, and even change OVP limits.
• Investigate GaN-FET retrofits for the primary bridge to push peak efficiency past 94 %.
• Study IEC 62368-1 Annex T.2 for clearance/creepage if you repurpose the PSU in commercial gear.
Your DPS-800 turns off because the internal firmware never sees the “all-clear” PSKILL# signal and therefore executes a 30-second safety shut-down. Ground PSKILL# and PS_ON#, tie the +12 V sense pin to the output, and provide at least a small load during first power-up. This three-jumper modification is sufficient for every known GB/GN revision and eliminates the time-out while retaining OCP, OVP and OTP protections. Replace ageing standby capacitors and keep the original fan (or emulate its tach) for long-term reliability.