M VII Power Switch Innards

[JPG]

Most of us have not been inside a Mark VII power switch. I had one apart last week and took some pix. It had some problems.

The switch is I believe a modified electric stove switch by GE.

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I call your attention to the mounting holes. The phenolic is soft and deforms over time. I recommend a couple of small flat washers to minimize that when reinstalling.

The phenolic cover merely pries off. It snaps back into place.
The large round hole is a lamp socket for the pilot light. An additional strap(not shown) is secured in the small hole near the top center and provides the center connection to the lamp.

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Once inside a problem becomes apparent. The power switch leaf springs have been over heated.

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Next apparent problem is the separated parts that were initially staked together. All the terminals are staked, but this one has an extra requirement that has failed(separated which makes the terminal and it's internal parts loose).

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Since the mechanical mechanism actually pushes the contacts open, they rely on leaf spring tension to close the contacts when not pushed. A loose terminal makes that unreliable.

A word about that mechanical stuff. There are three sliding parts beneath the contact 'springs'. On the reverse side these are pushed by depression of the fwd/ rev/ stop buttons. The fwd pushes one outer slide and the center slide. The center slide allows the power on contacts to make. The outer slide connects the direction contacts. The rev pushes the other outer slide and also the center slide. Again the center slide allows the power contacts to make. The outer slide reverses the direction contacts.

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The loose terminal was Soldered to reconnect the parts both electrically and mechanically.

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The switch was checked and all contacts make/open correctly. However the power springs have lost their temper and may not be reliable. The direction switching is I believe reliable.

[everettdavis]

Thank you. That is helpful.

Everett