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manual abstract
17 2. EXPLODED VIEW, PCB ASSEMBLIES AND PARTS LIST ................. 19 CAUTION A Parts marked with this sign are safety critical components. They must always be replaced with identical components. Refer to the Fostex Parts List and ensure exact replacement, NOTES * Adjustment procedures are given in this manual which also includes a Parts List and schematic diagrams to assist the service technician in maintaining the Model EN3020 Please feel free to contact the nearest Fostex Dealer and Distributor, or write directly to a Fostex office, the addresses of which are printed on the back cover of this manual. 16 1. METHOD OF MEASUREMENT EN3020 OSCILLO- DISTORTION METER Fig- 1 Circuit for measurement 1. Filter response measurement Measuring equipments are connected to the EN3020 as shown in Fig. 1. Figures 2 and 3 are measurement data for crossover frequencies of 600Hz and 7KHz and Fig. 2 is the response for the 12dB/oct- filter and Fig. 3 for the 18dB/oct. filter- For l^db/oct. type For ItidB/oct. type Fig- 2 Fig. 3 The crossover frequencies are set at the -6dB attenuation point for the 12dB/oct. filter and at the -3dB attenuation point for the 18dB/oct. filter. In regards to the crossover frequencies, there should be no problem if the attenuation point deviation is within ±1.5dB. (a) Low pass filter response When taking measurements for 600Hz crossover frequency, for example, a 100Hz signal at OdB (0.775V) is applied to the input terminal and assuming the output voltage for this input level to be OdB, measurements are taken by changing the frequencies over the required range. 17 (b) Band pass filter response The frequency is changed in the same way as above and measurements taken at the band pass filter output terminal. (c) High pass filter response The frequency is changed in the same way over the required range and measurements taken at the high pass filter output terminal. The above procedures (a) ^ (c) are also taken to measure each other crossover frequency responses. It is important at taking the above measurements to be sure the reference level is set at a point on the frequency range where the level will not be affected by the crossover frequency. 2. Input-output response Upon completing measurements in above 1., a 100Hz signal for the low pass filter, 1 KHz for the band pass filter, and lOKHz for the high pass filter, respectively, are applied at +4dB (1.23V) to each filter input terminal and confirm that the output voltage of each filter is +4dB, ±ldB. 3* Distortion A +4dB (1.23V) signal is applied to the input terminal and the output voltage distortion is measured by a Distortion Meter. The resulting values should be: LOW filter 100Hz Less than 0.06% MID filter 1 KHz " ” 0.02% HIGH filter lOKHz 11 “ 0.02% 4, Residual noise The LEVEL control knob is set at " 00 " without any signal applied to the input and the level at each OUTPUT terminal measured in ,rdB.,r The residual noise figure thus measured should be less than -80dB {using a band pass filter for 20 ^ 20,000Hz). 2. EXPLODED VIEW. PCB ASSEMBLIES AND PARTS LIST ASSEMBLING HARDWARE CODING LIST All screws conform to ISO standards, and have crossrecessed heads, unless otherwise noted ISO screws have the head inscribed with a point as in the figure to the right. FOR EXAMPLE B M 3 x 6 Inner dia. for washers and nuts 'w7' -----------Length m mm (LI - - --------Diameter in mm {D) * . ---------Meinc System - —-------Nomenclature -Ao * CODE NAME TYPE CODE NAME TYPE P Pjn H*ad Screw H D TW Trim Washer 1 Countersunk J -S’ 5 UJ T SlOVR Head Screw 1T h 0TFTIffilTff| d -1 N Hex Nul CC o 00 UJ B Binding Head Screw CE UJ I L Lug Z X o < F l*t COunlRiSljnk He*[j ScrBVLf « 5 THW Thrusi Wasnsr ( Poly Washer I 2 0 fjv*l Cf>unt«r$unk Hear! Screw £jE™5 HSF Hex Scicket Setscrew (Hat Point j ma 3 PWH Pan Washtr Head Screw £ UJ ir HSC Hex Socket Setscrew 1 Cup Pomi I OJ Ï UJ CC RW Round Head Wood Screw in K LU [/> SSF Sloued Socket S^iscrew (Flat Pomi ) ®ü 3 o t/> O O FW rial Couniersunk Wuud Screw ^¡nnH№- SSC Sloued Suckei Setscrew 1 Cup Pomi ) ©3 o 5 OW Oval Cuufiiersunk Wotxd Screw H HSB Hex Soket Heafl Bolt —, 5 PTP Purt Hiad Soil Tapping Screw (fi type 1 o ffl HB He» Head Bolt LU (L O t/2 PTPWH Pan washer Head Self Tapping Screw (6 type 1 0EÜ5 ER F Fling ( Helgjning Washer )