Note 4 - Revenue From Contracts With Customers - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net revenues	$ 14,632	$ 20,160	$ 47,046	$ 60,128
Semiconductor Market [Member]
Net revenues	7,126	11,415	24,878	34,997
Industrial Market [Member]
Net revenues	5,758	5,576	15,983	16,229
Telecommunications Market [Member]
Net revenues	153	2,051	1,437	4,673
Other Non-semiconductors Markets [Member]
Net revenues	1,595	1,118	4,748	4,229
Thermal Testing Products [Member]
Net revenues	4,568	6,259	13,817	17,981
Induction Heating Products [Member]
Net revenues	4,160	6,150	14,232	17,709
Semiconductor Production Test Products [Member]
Net revenues	3,841	5,245	12,734	17,393
Service and Other Products [Member]
Net revenues	2,063	2,506	6,263	7,045
End User [Member]
Net revenues	13,167	17,186	42,310	51,687
OEM and Integrators [Member]
Net revenues	$ 1,465	$ 2,974	$ 4,736	$ 8,441