Description

Product Introduction

The sterilization control panel at a medical device manufacturer had a 90-30 rack driving eight 24 V solenoid valves — each drawing 150 mA. Total load was 1.2 A. The standard DIMA had a 1 A auxiliary output — not enough. The plant was using two separate power supplies: one for the PLC rack and one for the solenoids. Then I spotted a DS3820DIMC in the warehouse — a 1.5 A variant with the same reinforced isolation. It’s the same 115 VAC input, same +5 V at 12 A, but the +24 V aux is 1.5 A instead of 1 A. We wired all eight solenoids to it, and the system ran for three years without a single power supply failure. I’ve only ever seen two of these in my career. This is one of them.

The GE DS3820DIMC is a dual-output AC-input power supply for the Series 90-30 rack. It takes 85–132 VAC — 115 VAC nominal — and produces a +5 V output at 12 A for the backplane and a +24 V output at 1.5 A for external loads — multiple relays, solenoids, or higher-current medical devices. The key feature is reinforced isolation: the +24 V output is fully isolated from the +5 V output with 3,000 VAC isolation — double insulation (2 x 1,500 V). The total power is 96 W (60 W + 36 W), derated to 85 W continuous. The unit is 5.4″ deep — the high-current 24 V transformer and reinforced isolation take space. The critical warning: this is a 115 VAC-only unit. No 240 VAC. No exceptions.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

Here’s our procedure for the DS3820DIMC — reinforced isolation verification, high-current 24 V testing, and the 115 VAC-only check.

1. Incoming Verification

OEM box check — GE holographic seal, part number matches “DS3820DIMC.” Date code recorded. Visual: the baseplate is GE blue. The unit is 5.4″ deep — the largest heatsink in the DS3820 series. The reinforced isolation transformer is larger than the DIMA variant. The label states “115 VAC Only” and “Reinforced Isolation, 24 V 1.5 A.” Accessories: terminal block cover present. Terminal block has six positions: L, N, GND, +5 V, COM, +24 V, COM2 — with COM and COM2 clearly separate.

2. Live Functional Test

We mount the unit on our test backplane. Input from a Variac set to 115 VAC, 60 Hz. Power-on: the green OK LED lights within 1.5 seconds. No load outputs: +5.02 V, +24.1 V. We load the +5 V to 10 A and the +24 V to 1.2 A — total 50 W + 28.8 W = 78.8 W. Outputs hold: +4.98 V, +23.7 V. Then we test the +5 V at 12 A (60 W) and the +24 V at 1.0 A (24 W) — total 84 W. Outputs: +4.95 V, +23.6 V. Then we test the +24 V at 1.5 A (36 W) with the +5 V at 8 A (40 W) — total 76 W. Outputs: +4.98 V, +23.3 V. Reinforced isolation test: apply 3,000 VAC between +5 V COM and +24 V COM2 for 1 minute — no breakdown. Leakage current at 250 VAC: 4 µA — below the 10 µA spec. Creepage measurement: 9 mm. 24-hour continuous run: +5 V at 10 A, +24 V at 1.0 A, 115 VAC, ambient 35 °C. Heatsink temp stabilizes at 72 °C.

3. Electrical Parameters

Insulation resistance: Fluke 1587 megger at 500 V between input (L/N shorted) and output — >10 MΩ. Between +5 V COM and +24 V COM2 — >20 MΩ. Ground continuity: <0.1 Ω. No hi-pot — the 3,000 VAC test is the hi-pot.

4. Firmware Verification

No firmware. We record the date code and check the flyback controller (UC3844) and the 24 V secondary rectifier — it’s a larger Schottky diode rated for 3 A.

5. Final QC & Packaging

QC log includes output measurements, reinforced isolation test results, leakage current measurement, and a photo of the larger transformer and heatsink. The unit goes into a fresh anti-static bag with a desiccant pack. Bubble wrap, double-wall carton. QC Passed label with date. We attach a large warning sticker: “115 VAC ONLY — REINFORCED ISOLATION — DO NOT CONNECT TO 240 VAC.”

Field Replacement Pitfalls

1. 115 VAC Only — No Exceptions

The DIMC is a 115 VAC-only unit. I saw a site where a tech connected it to 240 VAC — the input capacitor exploded, and the reinforced isolation transformer’s primary shorted. Check your site’s voltage before ordering. If you have 240 VAC, you need a 240 VAC-capable unit. The reinforced isolation won’t save you from overvoltage on the input.

❗ 2. Total Power — 96 W Shared, But You Can’t Run Both at Maximum

The DIMC has a total power of 96 W. The +5 V at 12 A is 60 W. The +24 V at 1.5 A is 36 W. You can’t run both at maximum simultaneously — that would be 96 W, which is the absolute limit. At 96 W, the unit runs at 78 °C in a 35 °C ambient — close to the 85 °C thermal shutdown. Keep total power under 85 W for continuous operation. That means if you’re using the +5 V at 12 A (60 W), limit the +24 V to 1.0 A (24 W) — total 84 W. If you need the +24 V at 1.5 A (36 W), limit the +5 V to 10 A (50 W) — total 86 W. Plan your load accordingly.

3. Reinforced Isolation — Don’t Defeat It

The reinforced isolation is 3,000 VAC. I saw a site where a technician tied COM2 to COM to “fix a ground issue.” The leakage current jumped from 4 µA to 500 µA, and the medical device failed its safety test. Keep COM2 separate from COM. Connect COM2 to cabinet earth if you need a ground reference, but never connect it to COM. The reinforced isolation is required for medical applications — defeating it voids the certification.

4. Cabinet Depth — 5.4 Inches

The DIMC is 5.4″ deep — the deepest in the DS3820 series. I saw a site where they ordered it for a 5.0″ cabinet — the door wouldn’t close. Measure your cabinet depth before ordering. If you’ve got less than 6.0″ of clearance, this unit won’t fit. Consider using the DIMA (1 A aux, 5.2″) and adding an external isolated supply if you need more current.

5. 24 V Output — 1.5 A, But Watch the Inrush

The +24 V output is 1.5 A continuous. If you’re driving solenoid valves, the inrush current can be 2–3× the holding current. A 150 mA solenoid can draw 400 mA for 50 ms during actuation. If you have eight solenoids and they all actuate at the same time, the inrush is 3.2 A — well over the 1.5 A rating. The +24 V output will drop to 18 V, and the solenoids may not actuate. Stagger the actuation timing of your solenoids to avoid simultaneous inrush. Or use the +24 V output to drive solid-state relays that switch an external 24 V supply. The DIMC’s control loop is optimized for steady loads, not high-inrush pulsed loads.

New Original vs. Refurbished: Why It Matters

The DS3820DIMC is the rarest variant in the entire DS3820 family — GE made fewer than 30 units. Our stock came from a single source: a cancelled medical device manufacturing project in Texas. These units were built in 2017 and stored in a climate-controlled facility.

What you’re buying: The high-current reinforced-isolation supply with the exact transformer, heatsink, and rectifiers GE specified. The isolation transformer has triple-insulated wire, an additional tape layer, and 9 mm creepage. The output rectifier is a 3 A Schottky diode — oversized for reliability. Refurbished units almost never have the original components — they use a standard transformer and a 2 A diode. Failure rate on refurbished DIMC units is around 30% in 18 months — the transformer fails the 3,000 VAC hi-pot test, or the diode overheats at 1.5 A. New surplus units have a 3% failure rate.

Real cost of a refurbished failure: The reinforced isolation fails. The +24 V output shorts to the +5 V output. The medical device’s patient-connected circuit is damaged — 10,000 in repairs. The plant loses its medical certification — 50,000 in compliance costs. The price difference between refurbished (3,500) and new surplus (5,500) is $2,000. That’s less than 4% of the total cost of a single failure.

What we provide as proof: OEM box photo, date code, a photo of the reinforced isolation transformer and the 3 A Schottky diode, our 3,000 VAC isolation test results, leakage current measurement (<10 µA), creepage distance verification (9 mm), and a full load test at 1.5 A on the +24 V output.

Pricing context: Our price sits 50–60% above refurbished alternatives but 25–30% below GE’s 2016 list — about $7,000 adjusted. The delta covers sourcing, QC testing, reinforced isolation verification, and a 12-month warranty.

Performance Benchmarks & Test Results

Output regulation (measured June 2026)

• +5 V: no load = 5.02 V; 12 A = 4.95 V (1.4% regulation)
• +24 V: no load = 24.1 V; 1.5 A = 23.0 V (4.6% regulation — within ±5%)
• Load combination: +5 V at 10 A, +24 V at 1.0 A — outputs: +4.98 V, +23.7 V.
• Load combination: +5 V at 8 A, +24 V at 1.5 A — outputs: +4.98 V, +23.3 V.

Reinforced isolation (measured)

• +5 V COM to +24 V COM2: 2.3 GΩ at 500 V
• Applied 3,000 VAC for 1 minute: no breakdown. Leakage current at 250 VAC: 4 µA — below the 10 µA spec.
• Creepage distance: 9 mm — exceeding the 8 mm reinforced insulation requirement.

Ripple

• +5 V at 12 A: 38 mV peak-to-peak
• +24 V at 1.5 A: 140 mV peak-to-peak (spec <150 mV)

Cross-regulation

• When the +5 V load steps from 5 A to 12 A, the +24 V output droops from 23.6 V to 23.2 V — 0.4 V drop. Recovers in 4 ms.
• When the +24 V load steps from 0 to 1.5 A, the +5 V drops from 4.98 V to 4.95 V — 0.03 V drop.

Thermal performance

• 85 W load, 115 VAC, 25 °C ambient: heatsink temp after 8 hours = 72 °C. Isolation transformer at 68 °C.
• 85 W load, 40 °C ambient: heatsink reached 84 °C after 6 hours — near the 85 °C shutdown. Derating: above 40 °C ambient, reduce total power by 2 W per °C. At 45 °C, max 75 W. At 50 °C, max 65 W. At 55 °C, max 55 W.

Efficiency

• 85 W load, 115 VAC: input power = 105 W, output = 85 W. Efficiency = 81%.

Hold-up time

• 115 VAC, full load: +5 V held >4.85 V for 22 ms. +24 V holds for 16 ms — the higher current draws down the aux output faster.

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