Discontinued Operations (Details)				3 Months Ended		9 Months Ended
	Oct. 29, 2019 USD ($)	Feb. 22, 2019 USD ($)	Jun. 29, 2018 USD ($)	Jan. 25, 2020 USD ($) contract	Jan. 26, 2019 USD ($)	Jan. 25, 2020 USD ($) contract	Jan. 26, 2019 USD ($)
Discontinued operations
Amount of alleged damages	$ 1,700,000	$ 6,500,000
Statement of operations
Net loss from discontinued operations					$ (62,000)		$ (2,511,000)
Gain on sale of business, net of tax expense of $2,463							8,452,000
Tax expense							2,463,000
Net (loss) income from discontinued operations					(62,000)		5,941,000
EES Business | Disposed of by sale
Discontinued operations
Cash consideration received			$ 31,994,000
Gain on sale of business			11,420,000
Amount of reduction to gain resulting from a working capital adjustment							505,000
Working capital dispute			922,000
Amounts recorded in the consolidated financial statements			0
Statement of operations
Net Sales							4,256,000
Cost of sales					54,000		5,080,000
Gross margin					(54,000)		(824,000)
Selling, general and administrative					14,000		1,517,000
Research and development					34,000		1,075,000
Other income, net							1,000
Loss from discontinued operations before income taxes					(102,000)		(3,415,000)
Benefit for income taxes					(41,000)		(904,000)
Net loss from discontinued operations					(61,000)		(2,511,000)
Gain on sale of business, net of tax expense of $2,463					(1,000)		8,452,000
Tax expense							2,463,000
Net (loss) income from discontinued operations					(62,000)		5,941,000
EES Business | Disposed of by sale | Other income (expense)
Statement of operations
Net Sales				$ 57,000	$ 657,000	$ 545,000	$ 2,013,000
Holdback | Disposed of by sale
Discontinued operations
Cash consideration received			$ 6,500,000
Number of remaining contracts | contract				2		2