Gates_BC-1T_user_WD8DAS.pdf

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1、BC-lT/BC-5OOT/BC-250T Jll lhh4 wjii- E-25534 Schematic-Overall BC-IT. E-25569 Schematic-Overall BC-50OT. -25582 Schematic-Overall BC-250T. 1. Change Value of R2 on Oscillator Unit from 150 ohms, 2 watt to 3900 ohms, 2 watt. 2. Add Cll, 100 mmfd. cap across L3. Per ECN-7482 Date: 5/29/58 Per ECN-7496

2、 Date: 6/26/58 ADDENDA SHEET INSTALLATION INSTRUCTIONS FOR REMOTE CONTROL IN GATES TRANSMITTERS BC-lT, BC+OOT, BC-25OT Refer to the folio-zing overall transmitter schematic diagrams: BC-1T - E=.2553L:. BC-50GT - E-25569 BC-2:3T - E-25582 A steel plate, drilled for mounting the M-4719 plate voltage k

3、it, M4720 plate current kit and M-4703 rheostat assembly is available for the- installer:s usen Tapped mounting holes for this plate have been provided in the cabinet corner supports, directly beneath the terminal boards and contactors (right side of transmitter as viewed from front), Photographs sh

4、owing the remote control kits in place is included v.ith these instructions, M-4703 Motor Rheostat Assembly As viewed from the rheostat end of this assembly, with the three rheostat terminals to the left, strap the center terminal (arm) to the top terminal. Since application of increasets voltage br

5、ings about clockv:lich runs upward to the final amplifier RF choke L-9, Remove this wire from the cable until sufficient leng;!i is available, then connect to one of the motor rheo.stat terminals, iising Packard cable or a high voltage equivalent, run a lead from the other rheostat terminal to this

6、same modula- tion reactor terminal discussed in Step 1, Set the trans- mitter vol.tage control R-l.4, for maximum voltage (minimum resistancejo The control circuit hook-up between the M-4703 motor and remote control unit is explained in the Remote Control instruction book, -l- 1. 2. 1. 2. 3. 4. 5. P

7、late Voltage Extension Kit M-4719 Using Packard cable or a high voltage equivalent, connect the M-4719 WV terminal to the motor rheostat terminal furthermost from the pcwer supply. Do not connect to the rheostat terminal which goes to the modulation reactor. Connect the M-4719 kit terminal rrG*t to

8、a good ground point within the transmitter. Refer to the Remote Control instruction book for connection of meter sample voLtage to remote control unit, Plate Current Extension Kit M-4720 The plate current kit is to be connected between the lower end of P.A. overload relay K-6 and ground. A ground le

9、ad runs from a chassis ground terminal to one of the coil terminals on K-7 modulator overload relay, thence to one coil terminal of K-6 P.A. overload relay. Clip out the portion between K-6 and K-7. K-7 is to retain its direct chassis ground since we want only P.A. current to flow through the plate

10、current kit. Both K-6 and K-7 must retain their shunt resistors directly across their respective. coils, The llGf terminal of the two-termin. strip on kit M-4720 connects to a good ground point within the transmitter. Run a lead from the other terminal, upward to the K-6 terminal which was formerly

11、grounded. Refer to the Remote Control instruction book for connection qf sampling voltage to remote control unit. Remote Plate Start-Stop Circuitry The BC-lT, BC-SOOT and BC-250T overall schematic diagrams plainly in- dicate the necessary connections for filament and plate remote control. The plate

12、start-stop circuitry consists merely of shunting the trans- mitter plate-start switch with a set of normally open remote control contacts, The plate-stop function is accomplished by connecting a set of normally closed remote contacts in series with the transmitter plate-stop switch. Remote Filament

13、Start-Stop Circuitry Note that a jumper is to be removed in the filament contactor circuit. Removal of this jumper disables the holding contacts on the filament contactor. A set of remote normally-open contacts shunted across the trensmitters f-ilament-start switch will then serve as filament start

14、-2- and hold, satisfying FCC requirements for a lfail-safel.circuit, If the telephone line between studio and transmitter fails, or if the remote control equipment becomes defective the remote holding con- tacts open. This, in turn, causes the filament contactor to drop out, removing the transmitter

15、 from the air. In multiple transmitter installations, the filament R-F, Driver Unit Schematic, Audio Input/Cathode Follower Overall Cabinet Dimensicns Simplified Schematic, Control System High Voltage Power Sup 1 Int. Voltage (600/65OVP Power Supply Bias Supply Power Amplifier Schematic Overall Sche

16、matic l/3/5: 4. 5. 6. 7. 2 10. 11. 12. 13. 14. 15. 16. 17. 18. Power output, 1000 watts, The Gates BC4T can be satis- factorily operated at 1100 w atts output, if necessary to overcome losses in transmission lines and/or phasing equip- ment. Frequency Range - 1600 KC to 540 KC. Power Supply -230 vol

17、t, 50/6o cy. 2 wire. Power Consumption - Approximately 3560 watts with normal program modulation of 85%. Frequency Stability - OOO cycles. Audio Input Impedance - 150/250/600 ohms. Distortion - 3% or less, 50 to 10,000 cycles, measured at 95% modulation. Noise - Minus 60 DB below 100% modulation. Ca

18、rrier Shift - 3%, or less, O-100% modulation. Output Impedance - 540-1600 KC. To match 50/70 ohms at all frequencies Coupling unit available for other impedances, Tubes used - One 12BY7A Oscillator One 12BY7A First IPA Twa 6BG6G Second IPA (parallel operated) Two 833A Power Amp. (parallel operated)

19、Two 6BG6G Input Audio Two 6BG6G Cathode Follower Audio Drivers. Two 8338 Class tBrt Modulators One 5R4GY Bias Rectifier Two 8668 Intermediate Voltage Rectifier (600/650) Two 8008 High Voltage Rectifier (25OOV) Crystals used - Provision made for two vacuum mounted ovenless type crystal assemblies, ea

20、ch switchable into oscillator circuit from front panel. Printed Wiring -5 - The oscillator and first IPA, the Radio Frequency driver the Audio input/cathode follower stage and the feed back ladder assembly are designed around printed wiring. Dummy Antenna - Self-contained 51.5 ohm dummy antenna capa

21、ble of handling 100% modulated transmitter output. Ventilation - Two fans in cabinet top. Renewal air filter in cabinet front. 11/lCRIPTION 1. geJ1 dimensions 76 high,.36-l/16 wide and 31-29/32. Back and right hand side are of bolt-on construction. 2. Flobc space required 3. - 8 sq. ft. Front doar s

22、wing is Zen. ;+!eight ) in operating condition - 800 pounds. SECTION III INSTALLATION. This instruction book affords valuable information for persons who are installing and operating the Gates BC-J.T transmitter. The following mentioned points should be studied so that the unpacking and setting up p

23、rocedure will be well in mind when doing the actual work. 1. Check all packing lists for materials supplied. 2. Study the instruction book before attempting to set up 3. the equipment. Have the transmitter location clean so that the various parts can be safely placed out of harms way when they are u

24、npacked. 4. It is preferable to have a mounting base, set in place, upon which the transmitter can be set. This base can be made from 2 X 4 lumber dimensioned as shown in Gates Drawing A30585. It should be painted, preferably black. This base should be lagged to the floor and measures taken to insur

25、e that the top side of the frame is perfectly level. This will give a good, solid, level base on which the transmit- ter can be set, This procedure also allows the external transmitter wiring to enter the cabinet from practically any point underneath and be run to the entry holes provi- ded in the b

26、ase of the cabinet. 5. Use heavy primary wire from the building switch box ter- minals to the transmitter fuse block. $4 or ;, 6 6. should be very suitable for these two leads. copper wire De sure the power company has installed large enough service for all the equipment, transmitter, li.oJhts, wate

27、r, pump, etc., which will be used at the transmitter site. 7. Do a good job of installing the equipment. Time spent in making the installation as good electrically and mechanically as possible, will pay off in the future by insuring less, off-the-air time, 11/1$/57 -2- DC-1T lKW, M5393 _- - SACTION

28、IV BC-IA! T%.iuS$.ITTtiR DATILS. The transmitter has been readied for shipment by having all tubes re- moved from their respective sockets, relay contacts have been blocked and tied and other parts such as parasitic suppressors, tube caps and leads, etc., tied down securely to prevent damage during

29、shipment. Vacuum enclosed time delay relays have been removed from their sockets. The power amplifier i;LF choke L9 also has been removed. The connector straps have been adequately tagged for easy, correct re-connection. These components have been adequately marked and packed in cartons that are in

30、turn safely secured within the transmitter. All of the power and modulating equipment has been shipped intact within the cabinet, thus relieving the installation engineer of the re-installa- tion of these components. Coil L13 located at top rear of cabinet has special mounting brackets provided to i

31、nsure safe travel, during transit0 These, along with all other packing material, string, tape, etc., should be removed from the components, The front door of the transmitter has been mechanically supported to the cabinet for shipping safety. Remove this support after installation. All relays should

32、be inspected for free travel of armatures and contact, The following information concerning the Gates BC-lT, pertains to its general construction and operation. It is highly desirable to study the various sections af the transmitter in order to completely under- stand and comprehend its operation, T

33、he complete transmitter is built in a welded steel cabinet with most of the low power RF and audio components mounted vertically on a farmed aluminum panel and shelf assembly. The high power modulators and power amplifier 833Afs are located on a tube shelf at the top of this basic assembly, The powe

34、r amplifier tuning and loading components are moun- ted on a large aluminum panei assembly at the top of the cabinet. This assembly is perforated to allow the heated air within the cabinet to pass through it and then drawn out of cabinet by the two tap fans. Located in the base of the-transmitter ar

35、e the heavy power components such as power transformers, rectifier, filament transformers, filter components, modulation choke and transformer, and rectifier tubes. Two removable air filters are located in the cabinet just at the bot- tom of the large front door. These filters can be changed while t

36、he transmitter is in speration. The frequency ef filter change will be determined by the transmitter location, En dusty locations, the fil:-. ters will, of caurse, become clogged very quickly-and should be changed as necessary to insure a full clean flew of air into the cabinet, The transmitter is c

37、ompletely dead front; there is a perfsrated metal i.nner shield extending downward from the power dplifier panel to the ll/lE(/57 -3- BC-1T Xmtr. air intake panel, The inner shield is joined to the air filter panel by means of two thumb Iquick off fasteners. Near the right hand fas- tener are the in

38、terlocks for the 600 volt and 2500 volt power supplies., All controls are available to the operator through a cut out in this perforated screen panel. If this panel is removed, the 600 volt and 2500 volt power supply interlocks function, removing these voltages from the transmitter, T:?is transmitte

39、r is crystal controlled by means of the MS422 oscillator unit which is located on the panel and shelf assembly. The crystal change-over switch 51, along with the frequency adjust variable con- densers Cl and C2 are conveniently located on the front control panel0 The ti,i5l+22 oscillator is mechanic

40、ally mountedto the side of the upright panel by means of four mounting screws. Power connections to oscilla- tor are made by a detachable plug assembly. For maintenance and ser- vice this oscillator can be quickly removed from the transmitter, The MS/+22 frequency control unit uses a 12BY7A tube con

41、nected circuit. wise as a electron coupled oscillator, controlled by a vacuum mounted, ovenless type crystal assembly. Positions for two crystals is pro- vided in the oscillator unit. The untuned plate circuit of the oscil- lator is capacity coupled to the grid of the first IPA, another 12BY7A physi

42、cally located in the small oscillator unit. This stage sperates under very conservative conditions and makes a fine isolation buffer between the oscillator and the R.F. driver. Due to the conservative operating potentials and the extremely low crystal currents, the MS422 oscillator unit has exceptio

43、nal frequency stability. The crystals are of a low temperature coefficient type which do not need a heated oven to maintain frequency well within FCC limits, Frequency trimmers Cl and C2 provide a small degree of fre- onnncy adjustment which may be required if the crystals age. The M54.22 oscillator

44、 unit is easily tuned to the operating frequency. No tuning ,is required for the oscillator itself, just insert the crystal, or crystals and set the crystal selector switch accordingly. The first IPA stage (12BY7A, V2 in unit) must be tuned, Provision is made to supply R.F. voltage from a resistive

45、divider at the output of the $15422 oscillator to a frequency monitor such as the Gates M2890. This monitor drive is available between terminal #27 on TBl and ground, See overall schematic E2553 in the left position Modulator #l, (I) is metered, in the right hand PO transformer T9 is of lOV, 20 ampe

46、re capacity and energizes the fila- ments of the two power amplifier tubes 6 and V7. The modulators are protected from severe overload by.relay K7. This : relay K7 is also provided with a coil shunt resistor, R22 making it possibleto adjust the pull-in point of the relay. Fomrmal program modulation

47、the modulator plate current should not exceed perhaps 400 i ma, ,Under sine wave audio conditions this current may rise to 650 map at the higher audio frequencies. A satisfactory setting for the over? Load relay would be around 700 ma. This will take care of accidental audio peaks that might go thro

48、ugh. This overload relay K7 has its normally open contacts connected in parallel with the normally open contacts of PcA. overload relay K6. If a modulator overload does oc-: curJ the K7 modulator overload relay pulls in causing 230 volts AC to TIP applied to the coil of Master Overload relay K3 whic

49、h in turn ener;? izes and pulls in to open the holding circuit of plate contactorf K2,. : is located on the panel and shelf assembly, directly above the module- tion transformer, T3.c, By means of a resistor/capacitordivider net- work out of, phase voltage is fed back to the audio input. The BC-1T :r:xmitter makes use of approximately 14 DB of feed back measured at 1000 cycles and 90% modulation. This feed back helps to reduce the bum and_-.