H744 +5V Regulator

The H744 +5V Regulator is one of the DEC standard modular regulators. It can produce an output current of up to 25A at an output voltage of +5V; the later (short-lived and rare) H7440 +5V Regulator could also produce up to 25A, and the replacement H7441 +5V Regulator up to 32A. All had over-current and over-voltage detection and protection.

It was a switching power supply, one of the earliest; however, the basic concept was quite different from later supplies of this type, as it was still quite low efficiency.

It takes as input AC at a voltage of 20V-30V, runs it through a diode bridge and filter capacitor to convert it to DC. That is then run through several large transistors controlled by a monolithic integrated circuit voltage regulator to produce the output.

The H744 and H7440 took their AC input on pins 6 and 7; the +5V output was on pins 2 and 5, and the ground return on pins 3 and 4; pins 1 and 8 were not used. In the H7441, pin 1 was also used for +5V output; the other pins were the same. Since it retained the use of only two pins for ground return, it's not clear what the utiliy of the third +5V pin was - perhaps it allowed machines to differentiate between H744's and H7441's?