DS3800HDDA1A1A | Full Suffix Mark V Discrete Input Card

Description

Product Introduction

The DS3800HDDA1A1A is the baseline configuration for GE’s 120V AC input board—screw-clamp terminals and 0.5A fusing on the field supply. This was the standard offering for Mark V cabinets in the 1990s, and many plants still have these boards in service today. The 0.5A fusing is adequate for the board’s own current draw—each input consumes about 5mA, so 32 channels draw only 160mA total. The fuse protects the board from a catastrophic short in the field wiring, which is rare for AC input circuits.

This board’s main advantage is compatibility with legacy 120V AC field wiring—a common voltage in older plants. The 1A1A suffix provides direct interchangeability with the original GE configurations. The screw-clamp terminals are robust and reliable, though we’ve noted that spring-cage variants (like 1E) can speed up terminations. The status LEDs on this board are a mixed blessing—they show the input state, which helps troubleshooting, but they also add about 5mA of current draw per channel, increasing the total load on your 120V AC source. If you’re sourcing from a small control transformer, those extra LEDs could push you over the limit.

Key Technical Specifications

Compatible Replacement Models

Frequently Asked Questions (FAQ)

Q: The 0.5A fuses on the 1A1A seem low. What happens if I have a short in the field wiring?
A: The 0.5A fuse will clear a short, but it’s sized for the field supply rail, not the individual channels. The board’s total current draw is only 160mA, so a 0.5A fuse gives you a 3x margin. However, the fuse is slow-blow, so it can handle brief inrush. If you have a hard short, the fuse will clear in about 10ms. The board itself will survive the short, but your field wiring might get hot—the fuse limits the current to 0.5A, which is safe for most wiring.

Q: The status LEDs on the 1A1A are powered from the field voltage. Does that affect the input current?
A: Yes. The LEDs add about 5mA each when the channel is active. So if all 32 channels are active, the total current draw is 32 × 5mA (optocoupler) + 32 × 5mA (LEDs) = 320mA. The 0.5A fuse is rated for 500mA, so you’re at 64% of capacity. If your source is a small control transformer, that 320mA might be a significant load. The LEDs are useful, but they do have a power cost.

Q: How do I set the input filter on the 1A1A?
A: The filter jumper is a small two-position block near the bottom edge of the board. Move the jumper to one position for 3ms filtering (fast response), or to the other for 10ms filtering (debounce). The default from GE was 10ms for mechanical contacts. We recommend the 3ms setting if you’re using solid-state outputs or proximity switches. If you’re using mechanical limit switches, the 10ms setting prevents false readings from contact bounce. Choose based on your specific inputs.

Q: The 1A1A has screw-clamp terminals. What torque spec should I use?
A: The terminal blocks are standard 5.08mm pitch screw-clamps. Torque spec is typically 0.5-0.6 Nm (4.4-5.3 lb-in). Over-torquing can strip the threads or crack the terminal block. We recommend using a small precision screwdriver and tightening until the wire doesn’t move. If you have a torque driver, set it to 0.5 Nm and you’re safe.

Q: I’m replacing an HDDA1A1A with an HDDA1B1B. Do I need to change the controller configuration?
A: No. The suffix variations affect only termination and fusing. The electronics are identical. The Mark V sees the same 32 input channels. No software changes are needed. The only change is physical wiring—spring-cage terminals require a different wire preparation. If your harness is already terminated for screw-clamp, you’ll need to re-terminate or use an adapter.

Q: The 1A1A has a 1.0A backplane current draw. Will that affect my rack’s power capacity?
A: The Mark V power supply typically provides 6A on the 5V rail. The 1A1A draws 1.0A maximum. If you have multiple high-current boards (e.g., several HDDAs or output boards), your total 5V current could exceed 6A. Check your total rack current before adding a new board. We’ve seen plants with four HDDAs and two output boards exceed the power supply limit—the result is intermittent resets. If you’re near the limit, consider using a higher-capacity power supply or redistributing boards across multiple racks. The 1A1A is a heavy load on the backplane—it’s a characteristic of the 120V AC input design.

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