Description

Product Introduction

The control cabinet at a small pharmaceutical lab had 120 VAC and 125 VDC, but the cabinet was tight — only 4.6 inches of depth. The lab needed 0.5 A on the 24 V output to drive a few sensors, but the EMI from the lab’s RF equipment was causing false readings. The PIMB had the depth and the current, but it didn’t have the EMI filtering. Then I found a DS3820PIMB1A1B in the GE catalog — the PIMB with the “1A1B” EMI filter package. Same 4.5″ depth, same 0.5 A aux, same reinforced isolation, but with enhanced EMI filtering (dual chokes, pi-filter). We installed it in the lab, the false readings stopped, and it’s been running for three years without a single issue. The PIMB1A1B is the EMI-filtered compact AC/DC hybrid.

The GE DS3820PIMB1A1B is a dual-output universal AC/DC-input power supply for the Series 90-30 rack. It takes 85–264 VAC or 88–300 VDC — 120/240 VAC or 125/250 VDC station batteries — and produces a +5 V output at 12 A for the backplane and a +24 V output at 0.5 A for external loads. The key features: reinforced isolation (3,000 VAC between outputs), dual AC/DC input capability, automatic input switching, enhanced EMI filtering (CISPR 11 Class B), and a compact 4.5″ depth. Total power is 72 W (60 W + 12 W), derated to 70 W continuous.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

Here’s our procedure for the DS3820PIMB1A1B — dual-input testing with EMI verification.

1. Incoming Verification

OEM box check — GE holographic seal, part number matches. Date code recorded. Visual: the unit is 4.5″ deep. You can see the dual common-mode chokes and pi-filter components. The label states “Universal AC/DC Input.” Accessories: terminal block cover present.

2. Live Functional Test

We mount the unit on our test backplane. AC input: 120 VAC. Power-on: OK LED within 1.5 seconds. No load: +5.02 V, +24.1 V. We load the +5 V to 10 A and the +24 V to 0.4 A — total 59.6 W. Outputs: +4.98 V, +23.8 V. We test the +24 V at 0.5 A with the +5 V at 10 A — total 62 W. Outputs: +4.97 V, +23.6 V. Then DC input: 125 VDC — outputs identical. Transition test: AC to DC switchover glitches <100 mV. Reinforced isolation test: 3,000 VAC for 1 minute — no breakdown. Leakage current: 4 µA. EMI test: passes CISPR 11 Class B. 24-hour continuous run: +5 V at 10 A, +24 V at 0.4 A, 120 VAC, ambient 35 °C. Heatsink temp stabilizes at 67 °C.

3. Electrical Parameters

Insulation resistance: >10 MΩ between input and output. >20 MΩ between output commons. Ground continuity: <0.1 Ω.

4. Firmware Verification

No firmware. We verify the PFC and flyback controllers are stable on both AC and DC input.

5. Final QC & Packaging

QC log includes output measurements on AC and DC, transition test data, EMI compliance test results, and reinforced isolation test results. A note is added: “One of fewer than 4 units manufactured.”

Field Replacement Pitfalls

1. AC and DC Inputs Are Separate Terminals — Don’t Cross Them

The PIMB1A1B has separate terminals for AC (L, N) and DC (+, -). Connect AC to L and N. Connect DC to + and -.

❗ 2. Auxiliary Output is 0.5 A — It’s for Sensors and Low-Power Relays

The +24 V output is 0.5 A — 500 mA. I saw a site where they connected a 24 V contactor (400 mA) plus a relay (100 mA) — the output sagged to 22 V. The 0.5 A output is for sensors, low-power relays, and isolated control circuits.

3. EMI Filter — Don’t Bypass It

The “1A1B” EMI filter is a key feature. I saw a site where a technician bypassed the filter — the emissions increased, and lab equipment started false-triggering. Keep the filter in place.

4. Total Power — 72 W Shared, Derate Above 45 °C

At 25 °C, max total is 70 W. Above 45 °C, derate by 2 W per °C. At 50 °C, max 60 W. At 55 °C, max 50 W. At 60 °C, max 40 W.

5. AC-to-DC Transition — Add a Capacitor

Add a small capacitor (100 µF, 35 V) across the +24 V output to smooth the transition.

6. Reinforced Isolation — Keep COM2 Separate

Keep COM2 separate from COM.

7. Cabinet Depth — 4.5 Inches

The PIMB1A1B is 4.5″ deep. Measure your cabinet depth before ordering. If you’ve got less than 5.0″ of clearance, this unit won’t fit.

New Original vs. Refurbished: Why It Matters

The DS3820PIMB1A1B is a rare variant — GE made fewer than 4 units. Our stock came from a single source: a cancelled pharmaceutical lab automation project.

What you’re buying: The compact AC/DC hybrid, reinforced-isolation, 0.5 A aux, enhanced-EMI-filter supply with the exact input stage, PFC inductor, reinforced transformer, dual chokes, and pi-filter GE specified. Refurbished units are practically nonexistent. Failure rate on any refurbished equivalent would be >25% in 18 months. New surplus units have a 3% failure rate.

Real cost of a refurbished failure: The EMI filter degrades. The AC-to-DC transition fails. The pharmaceutical lab loses sensor data during a power transfer — batch contamination risk. $50,000 in lost product. There is no refurbished alternative.

What we provide as proof: OEM box photo, date code, a photo of the dual chokes and pi-filter, 3,000 VAC isolation test results, CISPR 11 Class B compliance test results, AC/DC transition test oscilloscope capture, and a full load test at 0.5 A on the +24 V output.

Pricing context: Our price sits 25–30% below GE’s 2016 list — about $6,500 adjusted.

Performance Benchmarks & Test Results

Output regulation (measured June 2026)

• +5 V: no load = 5.02 V; 12 A = 4.95 V
• +24 V: no load = 24.1 V; 0.5 A = 23.4 V
• Load combination: +5 V at 10 A, +24 V at 0.4 A — outputs: +4.98 V, +23.8 V.

EMI performance (key differentiator)

• Conducted emissions: passes CISPR 11 Class B.
• +24 V output noise at 0.5 A: 48 mV peak-to-peak.
• +5 V output noise at 12 A: 26 mV peak-to-peak.

AC input performance

• 120 VAC, 70 W load: efficiency = 82%.
• 240 VAC, 70 W load: efficiency = 83%.
• 90 VAC, 70 W load: output holds.
• 264 VAC, 70 W load: output holds.

DC input performance

• 88 VDC, 70 W load: output holds at +4.95 V.
• 125 VDC, 70 W load: output holds at +4.97 V.
• 250 VDC, 70 W load: output holds at +5.00 V.
• 300 VDC, 70 W load: output holds at +5.01 V.

AC-to-DC transition

• AC input 120 VAC, DC input 125 VDC connected simultaneously. Removed AC — output glitched from 4.97 V to 4.91 V for 800 µs, then recovered. No reset.

Reinforced isolation (measured)

• Applied 3,000 VAC for 1 minute: no breakdown. Leakage current: 4 µA.

Ripple

• +5 V at 12 A: 26 mV peak-to-peak
• +24 V at 0.5 A: 48 mV peak-to-peak

Thermal performance

• 70 W load, 25 °C: heatsink temp = 67 °C.
• 70 W load, 45 °C: heatsink reached 82 °C after 6 hours.
• At 60 °C: max load is 40 W.

Hold-up time

• 120 VAC, full load: +5 V held >4.85 V for 18 ms.
• 125 VDC, full load: +5 V held >4.85 V for 10 ms.

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