Note 4 - Revenue From Contracts With Customers - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net revenues	$ 14,352	$ 21,097	$ 32,414	$ 39,968
Semiconductor Market [Member]
Net revenues	7,641	13,043	17,752	23,582
Industrial Market [Member]
Net revenues	4,279	5,000	10,225	10,653
Telecommunications Market [Member]
Net revenues	691	1,343	1,284	2,622
Other Non-semiconductors Markets [Member]
Net revenues	1,741	1,711	3,153	3,111
Thermal Testing Products [Member]
Net revenues	4,282	5,885	9,249	11,722
Induction Heating Products [Member]
Net revenues	4,321	5,937	10,072	11,559
Semiconductor Production Test Products [Member]
Net revenues	3,609	6,809	8,893	12,148
Service and Other Products [Member]
Net revenues	2,140	2,466	4,200	4,539
End User [Member]
Net revenues	13,106	18,173	29,143	34,502
OEM and Integrators [Member]
Net revenues	$ 1,246	$ 2,924	$ 3,271	$ 5,466