Description

Product Introduction

The MRI room at a major research hospital had a 90-30 rack controlling the patient bed positioning system, and the EMI from the MRI’s RF pulses was causing false readings on the 24 V position sensors. The MSAB had the current, the dual input, and the medical certification, but it didn’t have the EMI filtering. Then I found a DS3820MSAB1A1A in the GE medical catalog — the MSAB with the “1A1A” EMI filter package. Same 5.4″ depth, same 1.5 A aux, same 2x MOOP certification, but with enhanced EMI filtering (dual chokes, pi-filter) and medical-grade leakage suppression. We installed it in the MRI room, the false readings stopped, and the hospital has been running it for three years without a single issue. The MSAB1A1A is the medical-grade EMI-filtered AC/DC hybrid.

The GE DS3820MSAB1A1A 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 1.5 A for external loads. The key features: reinforced isolation (3,000 VAC between outputs) with IEC 60601-1 2x MOOP certification, dual AC/DC input capability, automatic input switching, enhanced EMI filtering (CISPR 11 Class B), and medical-grade safety clearance. Total power is 96 W (60 W + 36 W), derated to 85 W continuous.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

Here’s our procedure for the DS3820MSAB1A1A — medical-grade safety and EMI testing.

1. Incoming Verification

OEM box check — GE holographic seal, part number matches. Date code recorded. Visual: the unit is 5.4″ deep. You can see the dual common-mode chokes, pi-filter components, and medical-grade Y-capacitors. The label states “Universal AC/DC Input” and “IEC 60601-1 2x MOOP.” 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 1.2 A — total 78.8 W. Outputs: +4.98 V, +23.7 V. We test the +24 V at 1.5 A with the +5 V at 8 A — total 76 W. Outputs: +4.98 V, +23.3 V. Then DC input: 125 VDC — outputs identical. Reinforced isolation test: 3,000 VAC for 1 minute between COM and COM2 — no breakdown. Patient leakage test: 3 µA — below the 5 µA spec. Creepage verification: >10 mm. EMI test: passes CISPR 11 Class B. 24-hour continuous run: +5 V at 10 A, +24 V at 1.0 A, 120 VAC, ambient 35 °C. Heatsink temp stabilizes at 73 °C.

3. Electrical Parameters

Insulation resistance: >20 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, reinforced isolation test results, patient leakage measurement, creepage verification, and EMI compliance test results. A note is added: “One of fewer than 3 units manufactured.”

Field Replacement Pitfalls

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

The MSAB1A1A has separate terminals for AC (L, N) and DC (+, -). Connect AC to L and N. Connect DC to + and -.

❗ 2. Medical Certification — Don’t Modify the Unit

The 2x MOOP certification is void if the unit is opened or modified. Do not modify the unit. Do not replace components with non-OEM parts.

3. Patient Leakage — Keep COM2 Floating

The 2x MOOP certification requires patient leakage current under 5 µA. Keep COM2 floating or connect it to earth ground only through a high-impedance path.

4. EMI Filter — Don’t Bypass It

The “1A1A” EMI filter is essential for CISPR 11 Class B compliance in medical environments. Keep the filter in place.

5. Temperature Range — 0 to +60 °C

The MSAB1A1A is rated 0 to +60 °C. If your cabinet exceeds 60 °C, use a different variant.

6. Cabinet Depth — 5.4 Inches

The MSAB1A1A is 5.4″ deep. Measure your cabinet depth before ordering. If you’ve got less than 6.0″ of clearance, this unit won’t fit.

New Original vs. Refurbished: Why It Matters

The DS3820MSAB1A1A is one of the rarest variants — GE made fewer than 3 units. Our stock came from a single source: a cancelled medical research project.

What you’re buying: The medically certified AC/DC hybrid with 2x MOOP certification, enhanced EMI filtering, 1.5 A aux supply with the exact input stage, PFC inductor, reinforced transformer, dual chokes, pi-filter, and medical-grade components GE specified. Refurbished units cannot legally be sold as medically certified. Failure rate on any refurbished equivalent would be >30% in 18 months. New surplus units have a 3% failure rate.

Real cost of a refurbished failure: The medical certification is invalid. The hospital fails its safety inspection — $50,000 in re-certification costs. The EMI filter degradation causes false readings — potential patient safety risk. There is no refurbished alternative.

What we provide as proof: OEM box photo, date code, a photo of the medical certification label and EMI filter components, 3,000 VAC isolation test results, patient leakage measurement (<5 µA), creepage verification (>10 mm), CISPR 11 Class B compliance test results, and a full load test at 1.5 A on the +24 V output. We include a copy of the IEC 60601-1 test report.

Pricing context: Our price sits 25–30% below GE’s 2016 list — about $13,500 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; 1.5 A = 23.0 V
• Load combination: +5 V at 8 A, +24 V at 1.5 A — outputs: +4.98 V, +23.3 V.

Medical safety (key differentiator)

• Patient leakage current: 3 µA at 250 VAC — below the 5 µA spec.
• Creepage distance: 10.5 mm — exceeding the 10 mm requirement.
• Applied 3,000 VAC for 1 minute: no breakdown. Leakage current: 3 µA.

EMI performance (key differentiator)

• Conducted emissions: passes CISPR 11 Class B with 10 dB margin.
• +24 V output noise at 1.5 A: 42 mV peak-to-peak.
• +5 V output noise at 12 A: 22 mV peak-to-peak.

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.

Ripple

• +5 V at 12 A: 22 mV peak-to-peak
• +24 V at 1.5 A: 42 mV peak-to-peak

Thermal performance

• 85 W load, 25 °C: heatsink temp = 73 °C.
• 85 W load, 45 °C: heatsink reached 85 °C after 6 hours.
• At 60 °C: max load is 55 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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