User manual RACAL RA-117

[. . . ] RACAL RA. 117 MANUAL RACAL RA. 117 SERVICE MANUAL 9. 8. 1999 TECHNICAL SPECIFICATION INTRODUCTION INSTALLATION OPERATION BRIEF TECHNICAL DESCRIPTION DETAILED CIRCUIT DESCRIPTION MAINTENANCE SPURIOUS RESPONSES VALVE DATA FAULT DIAGNOSIS REPRESENTATIVE TEST DATA GENERAL SERVICING AND ALIGNMENT PROCEDURES DISMANTLING COMPONENT LIST 1 (RESISTORS, CAPACITORS, SWITCHES, PLUGS AND SOCKETS) COMPONENT LIST 2 (VALVES, CRYSTALS, INDUCTANCES, TRANSFORMATORS ETC. ) LIST OF ILLUSTRATIONS: FIG. 1 - REAR VIEW OF RECEIVER CHASSIS FIG. 2 - FRONT PANEL, RA. 117 FIG. 3 - RA. 117 BLOCK DIAGRAM FIG. 4 - SIMPLIFIED BALANCING CIRCUIT FIG. 5 - NOISE LIMITER CIRCUIT RACAL RA. 117 MANUAL FIG. 6 - TYPICAL SELECTIVITY CURVES FIG. 7 - TERMINAL TAG STRIP FIG. 8 - TOP VIEW OF RECEIVER FIG. 9 - FIRST V. F. O. FIG. 12 - 1. 7Mc/s OSCILLATOR / AMPLIFIER AND MIXER UNIT FIG. 13 - B. F. O. UNIT FIG. 14 - CRYSTAL CALIBRATOR UNIT FIG. 15 - KEY TO UNDER - CHASSIS LAYOUT FIG. 16 - R. F. ATTENUATOR FIG. 17 - SUPPLY FILTERS FIG. 18 - CRYSTAL OSCILLATOR / AMPLIFIER AND HARMONIC FILTER SYSTEM FIG. 19 - SECOND MIXER FIG. 20 - BAND - PASS FILTERS FIG. 21 - 100 kc/s I. F. [. . . ] This response may be eliminated by adjusting the 37. 5 Mc/s strap (L300 at second mixer anode). When the receiver is tuned to 3. 2 Mc/s the first v. f. o. This reaches the second mixer and combines with 37. 5 Mc/s givin a stable 6 Mc/s which may pass through the 2. 3 Mc/s BPF where it combines with the second v. f. o. running at 4. 4 Mc/s giving 1. 6 Mc/s which then follows normal paths. Switch R. F. RANGE Mc/s to WWIDEBAND 75-ohms. 1 Mc/s break-through responses appear at 0 and 1, 000 on the KILOCYCLES scale at each setting of the MEGACYCLES dial and are generally more prominent with wideband input. If the response is dependent upon the setting of the MEGACYCLES dial, the 1 Mc/s spectrum is probably breaking through to the first mixer stage. If the response is independent of the MEGACYCLES dial setting, it is due either to break-through of the second and/or third harmonic to the second or third mixer stage. Remove second mixer valve to eliminate this stage and so determine in which stage the break-through occurs. Spurious responses may occur at 4. 5, 5. 5 and/or 17. 5 Mc/s, if C42A and/ or C194A are open circuit. These responses are caused by the harmonics of the first v. f. o. breaking through to the second mixer stage and beating with the harmonics of the 37. 5 Mc/s heterodyne voltage. These responses may be detected at 100 kc/s intervals between 1 and 1. 5 Mc/s when the b. f. o. frequency is 100 kc/s and the receiver aerial input is tuned. RACAL RA. 117 SPURIOUS RESPONSES SECOND V. F. O. Responses may occur at 3. 8 and 4. 3 Mc/s with tuned aerial input. Ascertain that the first and second v. f. o. chassis is well bonded to the main chassis and the fixing screw are tight. NOTES: A failure in any one of the following capacitors C66, C92, C96, C97, C98, C103 or C104 may result in increased 'end of band' responses. These responses will disappear when the MEGACYCLE dial is detuned. The failure of C117, C327, C207, C208 or C214 can result in 'end of band' responses, or b. f. o. Detuning the MEGACYCLES dial will have no effect. Responses may occur at 1. 7 and 3. 4 Mc/s with tuned aerial input due to radiation from the 1. 7 Mc/s crystal oscillator. [. . . ] (8) Disconnect brown leads from pin 4 of V18 socket. (9) Disconnect blue leads from pin 7 of V21 socket. (10) Remove remaining three screws and crinckle washers to release b. f. o. 1. 7 MC/S OSCILLATOR/AMPLIFIER AND MIXER UNIT 11. [. . . ]