HP-Service-Note-412A-2A 电路图.pdf

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1、i c - i 41 2A-2A MODEL 412A DC VACUUM TUBE VOLTMETER REPLACEMENT OF RANGE SWITCH ASSEMBLY STOCK NO. 412A-19W KEEP SWITCH CLEAN. WEAR A PAIR OF RUBBER GLOVES WHEN HANDLING SWITCH. MAKE SOLDER CONNECTIONS QUICKLY AND CLEANLY. The Range Switch Assembly, Stock No. 412A-l9W is a pretested, direct replace

2、ment switch for the cabinet mounted Model 412A DC Vacuum Tube Volt- meter. The assembly is supplied with all switch mounted components .installed. Included are the RANGE, POLARITY, and FUNCTION switches as part of the prefabricated harness. Installation procedures for your cabinet mounted in- strume

3、nts are different from those required for your instruments designed for rack mounting. Replace- ment procedures for rack mounted instruments are covered in Service Notes 412AR-1A. The Range Switch Assembly in both instruments, however, is identical except for cabling and lead lengths. W Replacement

4、procedures require disconnecting input cable leads, removal of panel and old switches, and installation of new askmbly. The panel is replaced and input leads reconnected. Calibration completes the procedure. COMPONENTS FURNISHED FOR RANGE SWITCH REP LACE MENT Quantity Description Stock No. 1 Range S

5、witch Assembly. . , 412A-l9W 1 Switch Nut, 5-40 x 1/4 inch. . 0540-0001 1 Washer, internal lock #6 a 2190-0007 4 Tinnerman Speed Nut #6 , , . 0590-0005 4 2390-0007 Screw, 6-32 x 5/16 inch w/lockwasher . . . . . , . . W distribution fg4p REPLACEMENT PROCEDURE FOR CABINET MODEL I . i j Disconnect powe

6、r. Remove two screws at rear /$Refer to figure 1. and slide cabinet off instrument. Remove input circuit shield. Disconnect support post screw from rear of chassis, NUnsolder blue and brown wires from meter terminals . h o o s e n three bezel screws on one side. Remove three bezel screws on other si

7、de. Slide off bezel. D IN U1S.A. RadioFans.CN 收音机爱 好者资料库 Page 2 41 2A- 2A DC AMP OUl clot INPUT TERMINAL BRACKET Figure 1. Model 412A Left Side View T NED 00398-2 RadioFans.CN 收音机爱 好者资料库 4 1 2A- 2A CONDUCTOR CENTER CONDUCTOR L D - - 4 2 1 WHmE Figure 2. Connection Diagram for MA/OHMS, COM, and VOLTS

8、 CABLES (Cabinet Mounted Instrument Only) Page 3 i d Refer to figure 2. Very carefullyunsolder VOLTS, MA/OHMS, and COM cables at input terminals. Do not shorten leads. Note that OHMS lead is three c ductor cable. CUnsolder all wires from input terminals except knob from RANGE switch (#8 Allen). Loos

9、en outside Allen set screws only and remove FUNCTION and POLARITY switch knobs. 00398-2 / “Ii1)Remove panel mounting screws (11/32 in. open end wrench) and hardware including black insulators. Note positioning of black insulators between panel an9 chassis. Remove panel and set aside. Detach input te

10、rminal bracket from chassis. Hang bracket to side with black wire. k2)Detach FUNCTION switch (no wires need be un- / 3 soldered yet), I RadioFans.CN 收音机爱 好者资料库 Page 4 412A-2A R47-MAY BE JUMPER WIRE OR RESISTOR I ,GRAY Figure 3. Polarity Switch Wiring 4 3 ) Detach POLARITY switch (no wires need be un

11、- jldered yet). 4)Refer to figure 3. Unsolder yellow wire (to DC AMP terminals at rear) and black-orange wire (to R46 METER CAL control) from POLARITY switch. &) Unlace black, black-white, and brown wires to RANGE switch, d &)Refer to figure 4-10 in Operating and Service Manual. Remove black wire fr

12、om R19 (180 ohms) mounted on RANGE switch and leading to “B” input of modulator, &)Refer to figure 4. Unsolder yellow-white wire from R28 (100 megohms) located near R116, BIAS ADJ control. Unsolder violet-white wires to RANGE switch from other end of R28. k 8 ) Unsolder violet-orange wire from R33 (

13、1OK) and violet-white wire from R34 (136.7K) from R34. Both resistors are located on 7 lug terminal strip at rear of chassis. i19) Refer to figure 5. Unsolder brown-orange and pink-orange wires from rear wafer of RANGE switch. Note color code identification of these wires with respect to switch term

14、inals, j20) Unsolder green wire at junction of capacitor ClOl (.lpf) and resistor RlOl (470K) which is the “A” input to the modulator. 1 R33 - R34 OK ,137.6K 00398-2 - _I_ . - . -* . 4 12A- 2A Page 5 R27 INKIORANGE BROWN /ORANGE SWrrCH BRACKET Figure 5. Range Switch Bracket Detail , ,/21) Disconnect

15、 switch mounting bracket at rear of RANGE switch. 22) Remove RANGE switch panel mounting nut (1/2 in, nut driver) and washer, 23) Lift out old RANGE switch, 24) Strip and tin black-orange, yellow, pink-orange, brown-orange, and green chassis wires t o be con- nected to new RANGE, POLARITY and FUNCTI

16、ON switches. U CAUTION From this point on in procedure rubber gloves must be worn. Rubber gloves must be decon- taminated before use, preferably by wash- ing with Freon* (type TF or PC) Solvent, and allowing them to air dry. After clean- ing avoid contact with any substance other than replacement sw

17、itch or clean hand tools. 25)Remove switch bracket from rear of old switch and install on new switch. Do not tighten bracket nut (3/16 in, open end wrench), 26) Loosely set new RANGE switch in position. Dress cabling to avoid binding. 27) Dress cabling to POLARITY and FUNCTION switches toward chassi

18、s, 28)Loosely fit FUNCTION switch in place. Dress leads to avoid binding. Dress pink-white, white- orange, black-white, and green wires toward panel and input terminal bracket. Dress gray and white i v *Freon Solvent, a product of The Dupont Company, Wilmington 98, Delaware, is chemically and ther-

19、mally inert, with a very high purity rate. 00398-2 wires on other side of switch and toward input terminal bracket, -)Mount FUNCTION switch. Center lever in slot, Tighten screws (#6 x 5/16 in. binding head screws and #6 Tinnerman speed nut). 30)Orient RANGE switch and loosely install panel nut and w

20、asher (3/8 in. x 32 nut and 3/8 in. external lockwasher). Ad) Loosely mount RANGE switch bracket to chassis (#6 x 1 in. binding head screw, #6 external lockwasher, and #6 hex nut w/lockwasher). Adjust final position- ing of RANGE switch and tighten bracket screw. Tighten nut (3/16 in.) that holds br

21、acket on switch. Tighten panel mounting nut (1/2 in,). c &Push blue and brown meter wires thru cabling hole in chassis (with white-orange and black-orange wires). d53) Set POLARITY switch in position with switch terminal lugs pointing away from RANGE switch. Dress cabling for POWER switch and pilot

22、light in- side POLARITY switch bracket. Center lever in slot and tighten screws (#6 x 5/16 in, binding head screws and #6 Tinnerman speed nuts). &) Solder green wire from terminal lug on FUNCTION switch to junction of capacitor ClOl (.lpf) andresistor RlOl (470K) which is the “A” input to the modula

23、tor. head screws w/lockwashers and #6 x 5/16 in. nuts). J35) Install input terminal bracket (#6 x 5/16 i n . binding - i 36)Solder black wire from “B” input to modulator (junction of C103 and R105, etc,) to terminallug on S1A that is junction of R19 and R10, 180 and 9 meg- ohms, respectively. 37)Dre

24、ss brown wire from R45 (.l ohms) on S1C to terminal 3 of input terminal bracket. Do not solder. Do not shorten brown wire. &) Solder brown-orange wire from junction of C114 (.051 pf) and R117 (2.7 megohms) to terminal lug on RANGE switch wafer S1F to agree with figure 5. )Solder pink-orange wire fro

25、m R116, BIAS ADJ control, to SlF to agree with figure 5. do) Dress cabling from S1F wafer behind RANGE switch and close to chassis. Connect wires to 7 lug ter- minal strip at rear of chassis to agree with figure 4. 4 ) S o l d e r yellow wire from DC amplifier OUTPUT terminal lug nearest R36 (OHMS A

26、DJ. control) to POLARITY switch (see figure 3), 2) Refer to figure 3. Remove R47 from old POLARITY a resistor or a jumper wire. See Service Notes 412A-1. - I - 1 / ( switch and install on new switch. Note: R47 may be 4 3 3 ) Solder black-orange wire from R46 (METER CAL control) and yellow wire from

27、DC AMPLIFIER OUT- PUT terminal to POLARITY switch to agree with figure 3. Mount panel, Carefully install insulating spacers end wrench. Connect support post with If8 x 1/2 in. binding head screw. Mount pilot light (7/16 in. open end wrench). di ount power switch (9/16 in. open end wrench). Pilot lig

28、ht bulb may be removed for convenience. 46)Solder MA/OHMS, COM, and VOLTS cable leads and internal connecting wires to input terminals to agree with figure 2. 47)Solder blue (+) and brown (-) wires to meter terminals. 48)Scrape away accumulated flux from all solder joints, qarticularly in the input

29、circuit, After flux F - and tighten screws (#8 x 1 in.). Use 11/32 in. open I 4 i s removed from connecting terminals, wash area of each with Freon Solvent. Be careful not to allow solvent to contact Pyrofilm glass resistors on switch. These resistors are treated with a silicon “dry film” and should not be cleaned. ?. u 48) Install knobs. 50) Install bezel. ADJUSTMENTS 1) Warm up instrument for at least 15 minutes, 2)Refer to Section IV of Model 41% Operating and Service Manual. Complete all procedures in para- graphs 4-14 under “Adjustments”. 00398-2