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← Older revision		Revision as of 23:13, 15 June 2022
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	* [http://www.glitchwrks.com/2019/06/05/pdp1110-psu-repair Repairing the PDP-11/10 Power Supply]		* [http://www.glitchwrks.com/2019/06/05/pdp1110-psu-repair Repairing the PDP-11/10 Power Supply]

	[[Category: DEC ~~Hardware~~]]		[[Category: DEC Electrical]]

Jnc: Fairly complete

2019-06-10T19:35:03Z

Fairly complete

New page

A '''DEC Power Line Monitor''' (alternatively called a '''Power Control Board''', '''Regulator Board''' and '''+15V DC regulator''' in various [[Digital Equipment Corporation|DEC]] documents and maintenance prints) is a small [[printed circuit board|board]] used in the [[H742 Power Supply|H742/H7420]] and [[H765 Power System|H765]] [[power supply|power supplies]] to produce a modest amount of +15V [[Direct current|DC]] power, along with a [[line time clock]] signal, and AC and DC 'power OK' signals.

[[Image:DEC 5409730.jpg|thumb|right|300px|5409730 board]]

The initial board was the 5409730 board in the H742, replaced by an 5411086 board in the H7420; the latter board was also used in the H765. The main difference beween the two was that the latter had been upgraded to produce up to 4A of -15V, from the 1A of the former.

There were also significant differences between the two in how they interfaced to the rest of the system; the main difference beween the two was that the former produced outputs on a short pigtail which ran into a 12-[[pin]] Mate-n-Lok connector (female pins), whereas the latter has an edge connector which plugs into a connector at one end of a [[power harness]].

The latter was probably to allow use of different harnesses in different applications: the H7420 harness, for instance, terminates in a Mate-n-Lok connector with female pins, emulating the original H742; the H765 harness ends in a Mate-n-Loc connector with male pins, apparently to allow the mating connector on the power distribution panel to have female pins, in common with all the other connectors on that panel.

[[Image:DEC 5411086.jpg|thumb|right|300px|5411086 board, with edge connector at bottom]]

Other uses (such as in the [[MJ11 memory system|MJ11]] and [[MK11 memory system]]s) use different harnesses.

The former version of the board also brings its [[alternating current|AC]] input in on a 4-pin Mate-n-Lok connector secured to the board; the latter uses the two right-most contacts (in the image to the side); these are usually broken out to a separate connector in the harness (see, for example, the [[H765 Power System|7010138 harness]] used in the standard BA11-K.

==Issues==

Some components on the 5411086 board (such as the main bridge [[diode|rectifier]]) are not protected by an on-board [[fuse]]; if they fail 'closed', since AC to that board enters through contacts on the edge connector, those contacts may be damaged.

This is not an issue in the H7420, which has a fuse in the power harness feeding the card; the H765 has no such fuse, and the issue has been seen in the field with these units.

It is recommended that an in-line fuse be added to the supply harness in these units. Alternatively, a separate AC supply pigtail, holding an in-line fuse, can be installed, to avoid routing AC through the edge connector at all; this approach has the additional advantage of not needing a change to the original harness in the unit.

==External links==

* [http://www.glitchwrks.com/2019/06/05/pdp1110-psu-repair Repairing the PDP-11/10 Power Supply]

[[Category: DEC Hardware]]

DEC Power Line Monitor - Revision history

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