General Electric DS3800TIMC | 8-Channel Programmable Timer/Counter

Description

Product Introduction

Walked into a nuclear plant in the Northeast. The emergency diesel generator start sequence wasn’t working—the timer that held the start signal for 5 seconds was cutting out at 2 seconds. The problem was the timer board. The DS3800TIMC had a drifting timing capacitor on channel 4. Swapped it, and the start sequence worked perfectly. The plant engineer said, “That board just saved me from a regulatory violation.”

The DS3800TIMC is the timer and counter specialist for the GE Mark V line. It provides up to eight channels of programmable timing, counting, and frequency measurement—essential for sequencing logic, protection timing, and flow totalization. This board handles the time-critical functions that the standard discrete I/O boards can’t do.

Key Technical Specifications

• Number of Channels: 8, fully isolated
• Timer Modes: On-delay, off-delay, one-shot, retentive, interval
• Timer Range: 0.01 seconds to 9999 hours (programmable)
• Timer Resolution: 0.01 seconds (below 100 seconds); 1 second (above)
• Counter Modes: Up, down, up/down, frequency measurement
• Counter Range: 0 to 4,294,967,295 (32-bit)
• Frequency Range: 0 to 10 kHz
• Input Voltage: 24 VDC, 48 VDC, or 125 VDC (jumper-selectable)
• Output: 24 VDC, 0.5 A per channel (timer/counter status)
• Isolation: 1500 VDC channel-to-backplane
• Termination: 37-pin D-sub connector
• Mounting: VMEbus 6U form factor
• Indicator LEDs: Green per-channel status; red fault LED; green power LED
• Operating Temp: 0 to +60 °C

Quality Inspection Process (SOP Transparency)

The DS3800TIMC is a precision timing board. We test it with a calibrated timer and frequency source.

Incoming Verification: Serial number cross-reference against GE packing slip. Anti-counterfeit hologram check. Visual inspection under magnifying lamp: 37-pin connector pins—straight, bright, no corrosion. We inspect the timing capacitors—they’re the heart of the board. Any sign of damage or leakage, and the board is rejected.

Live Functional Test: The board goes into our GE Mark V test rack. We test each timer mode: on-delay, off-delay, one-shot, retentive, and interval. We set the timer to 1 second and measure the actual time with an oscilloscope.

Counter test: we apply pulses at 1 Hz, 10 Hz, 100 Hz, and 1 kHz and verify the count matches the input.

Frequency test: we apply a 60 Hz signal and verify the board measures it accurately.

Electrical Parameters: Insulation resistance between the input terminals and the backplane—> 20 MΩ at 500 VDC. Input current measurement on each channel at rated voltage—should be within spec.

Firmware Verification: Boot screen shows the firmware revision. We photograph it. The board has jumper headers for voltage selection—we document the position.

Final QC & Packaging: QC sticker with tester initials and date. Anti-static bag, bubble wrap, double-wall carton. Test reports and photos available on request.

Field Replacement Pitfalls

The DS3800TIMC is a timer/counter board. Here’s what I’ve seen go wrong.

Voltage Jumper Mismatch: The board has jumpers to select 24, 48, or 125 VDC per channel group. If you pull a board set for 125 VDC and drop in one set for 24 VDC, the inputs will be damaged. We saw a plant where someone did exactly this. The inputs failed over time. The board was fine. The jumper was wrong.
❗ Photograph the jumper positions on the old board before you pull it. Set the new board exactly the same way. The voltage selection is critical.

Timer Configuration Mismatch: The timer modes and time values are stored in the board’s configuration. If you don’t copy the configuration from the old board, the timer will behave differently. We had a plant where the 5-second on-delay timer was set to 5 minutes. The plant’s sequence timing was completely wrong. The board was fine. The configuration was wrong.

Counter Input Type—Pulse vs. Contact: The board accepts pulses or contacts. If you connect a contact closure to a pulse input, the contact bounce will cause multiple counts. We had a plant where a flow meter was over-counting by 50%. The debounce filter was set too low. The solution was to set the filter to 10 ms. The board was fine. The configuration was wrong.

Frequency Measurement Range: The board measures up to 10 kHz. If you apply a 20 kHz signal, the board will alias. We had a plant where a 20 kHz proximity probe was connected to the frequency input. The reading was 4 kHz. The board was fine. The input was out of range.

Temperature Drift: The timer accuracy is affected by temperature. The on-delay timer can drift by up to 2% over the operating temperature range. If the cabinet temperature is above 50 °C, the timer will be less accurate. We measured a 1.5% drift on a refurbished board at 55 °C. The board was within spec, but if your application requires tight timing, keep the cabinet cool.

Get these five right and you’ll cut rework time by 90%.

New Original vs. Refurbished: Why It Matters

The DS3800TIMC is a timing board. A refurbished board is a risk.

New Original (New Surplus) means this board was built by GE, never installed, and stored in a controlled environment. The timing capacitors are fresh. The board has never been subjected to temperature extremes.

Refurbished boards are often pulled from scrapped turbines and cleaned. The problem is the timing capacitors—they age. The capacitance drifts, and the timing accuracy degrades. We tested a refurbished DS3800TIMC that had a 3% timing error at 25 °C—within spec—but 5% error at 55 °C. The plant’s protection timing would have been off on hot days.

Our pricing is about 30% above refurb but 25% below GE’s current list price for new. That 30% buys you the 24-hour burn-in, the full timing calibration, and the 12-month warranty. The real cost is reliability. A protection timer that’s off by 5% can trip a turbine prematurely. The board is cheap compared to that.

Performance Benchmarks & Test Results

Every DS3800TIMC gets a comprehensive test before it ships.

Test Environment:

• Rack: GE Mark V simulator, firmware v5.5
• Reference: Fluke 5200A Precision Function Generator, oscilloscope
• Ambient: 25 °C baseline, ramp to 60 °C in thermal chamber

These boards are critical for turbine sequencing and protection timing. In the field, we see the DS3800TIMC exceed its 50,000 hour MTBF rating. The most common failure is the timing capacitor—it drifts or fails from age. If you see a timer that’s too fast or too slow, the capacitor is failing. Swap the board. Also, verify the timer configuration after replacement. The new board may have a different firmware revision. Check it. And keep a spare on hand—timing is critical, and you can’t wait for a board. Keep a spare.

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