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HP 456A, Operating And Servicing Manual

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Summary of Contents for 456A

Page 1: ...56A AC CURRENT PROBE SERIALS PREFIXED 103 PRINT O 3 61 I 00395 1 ...

Page 2: ...00395 1 OPERATING AND SERVICING MANUAL MODEL 456A SER IALS PREFIXED 103 AC CURRENT PROBE Copy ht HEWLETf ACK UD COM ANY 1961 ISOI AGE Mill ROAD AlO AlIO CALIFORNIA U S A Printed MAR 1961 ...

Page 3: ... 13 Replacing the Probe Cable REPLACEABLE PARTS 5 1 5 2 5 3 Introduction Table of Replaceable Parts Ordering Information 4 L 4 1 4 L 4 1 4 1 4 3 4 3 4 3 4 3 4 4 4 4 4 4 4 4 5 1 5 L 5 1 5 1 LIST O F IllUSTRATIONS Number Title L l General A rrangement of Model 456A 1 2 Model 456A AC Current Probe 1 3 Typical Change in F requency Response 2 1 2 2 2 3 2 4 2 5 with Load Capacitance Probe used with Mcxi...

Page 4: ... probe Less than 50 milliohms in series with 0 05 h This is approximately the induc tance of 1 1 2 inches of hookup wire Approximately 4 pf added from wire to ground For 1 2 amp input at least 50 db down For 10 rna input at least 70 db down Less than 50 a rms 100 a when ac powered 220 ohms at 1 kc Approximately 1 volt dc component Should work into load of not less than 100 000 ohms shunted by appr...

Page 5: ...or The probe operates with an accompanying small ampli fier to convert the ac current being measured to a pro portional voltage The current to voltage conversion factor is 1 millivolt output for 1 milliampere flowing th rough the probe Current readings can thus be taken directly from the voltage calibrations on the voltmeter or oscilloscope Table 1 2 is a list of instruments w hich can be used wit...

Page 6: ... The Model 456A is available either as a battery powered or ac powered instrument The AC Power Supply srock 456A 95B fits into the space nor mally occupied by the battery supply and takes the place of it electrically The ac power supply must be ordered separately When the 456A is powered with its own internal bat teries it is independent of power lines It may be used in the field with battery oper...

Page 7: ...ribed in text 00395 1 In this manner currents even below 10 microamperes can be measured 2 3 OPERAT IN G T HE PRO BE The probe jaws may be operated with one hand While holding the probe handle in the palm squeeze the flanges together with the fingers This action will open the jaws Move the probe to the vicinity of the insulated wire being measu red and slowly release the flanges until the jaws fit...

Page 8: ...by squeezing flanges on probe together 3 Connect ground clip to instrument under test if necessary see paragraph 2 5E Figure 2 2 2 2 Model 456A 4 t 1I t f RO 4 Read current being measured on meter or oscil loscope read millivolts as milliamperes S Note direction of arrow on probe Conventional current flow in direction of arrow gives positive going output voltage Opera tion 00395 1 ...

Page 9: ...n the signal being measured should preferably be kept below 1 2ampere Direct current below that value will have no effect on the measurement C ALTERNATING CURRENT FIELDS The probe is shielded against external ac magnetic and electric fields Extremely strong fields may cause an erroneous reading If a strong ac magnetic field 00395 1 is suspected rotate the empty probe head with the jaws closed If t...

Page 10: ...u may choose which side of the circuit to measure the current See figure 2 5 Note in figure 2 5 the probe measures the current flowing in the circuit on the same side as the wide side of the arrow on the probe Occasionally at high frequencies above 15 me a greatly magnified voltage effect exists at a particular frequency This effect is caused by a resonance be tween excessive external ground lead ...

Page 11: ... to the tube output capacity hp 456A PROBE HEAD Section II Paragraph 2 6 Cont d The probe is valuable in a number of other current equalizing applications EspeciaUy common among these are equalizing the input and output currents in push pull and balanced circuits in both transistor and tube applications Figure 2 6 Bucking OUt Capacitive Component of Plate Current 00395 1 2 5 2 6 ...

Page 12: ...results in a better frequency response lower input impedance dc bias stability lower distortion etc le 4 RD Figure 3 1 Equivalent Circuit 00395 1 The equivalent circuit can be thought of as shown in figure 3 1 where CL is the current gain of the tran sistor The transistors have internal resistances as shown Emitter resistance re is small but relevant to this discussion while the collector resistan...

Page 13: ...lowed extensive damage to the etched circuit board will result 1 Apply heat sparingly to lead of component to be replaced If lead of component passes through an eyelet in the circuit board apply heat on com ponent side of board If lead of component does not pass through an eyelet apply heat to con dUctor side of board 3 Bend clean tinned leads on new part and care fully insert through eyelets or h...

Page 14: ...tion unless otherwise specified It can be quickly and easily converted to operate from a nominal line 00395 1 voltage of either 115 or 230 volts and a frequency of 50 to 1000 cps To convert for 230 volt operation remove the short across R90 Turn the instrument off before doing any soldering 4 4 C HECKIN G THE BATTERIES Whenever trouble is encountered check the voltage at the BATTERY TEST terminals...

Page 15: ...il400D H L reads exactly 0 1 volt Model 456A 456A 5 Connect the OUTPUT cable of the 456A to the input of the 400D H L in place of the 470C Leave the wires still connected to the 470C 6 Read 400D H L Reading should be within sum of specifications of the 470C and 456A 7 Repeat above steps with 650A set at other fre quencies up to 100 kc If the 456A calibration or frequency response is poorer than te...

Page 16: ...illoscope should be less than 75 Jl volts 100 Jl volts with ac powered model If not check C94 power supply capacitor if ac powered or try replacing CRI Q1 or Q2 Check with 456A POWER switch off to see if ground loops exist If they do see paragraph 2 50 B CALIBRATION A ND FREQUENCY RESPONSE Perform the procedure illustrated in figure 4 2 Note that this test is used only for rough testing with readi...

Page 17: ...o the semi conductor Table 4 1 lists the tests which should be made after replacing the components 4 11 CALIBRATION Perform the procedure in figure 4 2 at 1 kc Adjust R9 Gain Set Potentiometer so that the voltage out is exactly 0 1 volt millivolts output equals milli amperes input If you can t reach calibration check R7 9 10 and 12 and the probe 4 4 Model 456A 4 12 FREQUEN CY R ESPO N S E Perform ...

Page 18: ...TEXT LOCKWASH ER l 2190 0012 PROBE CABLE ASSEMBLY COMPLETELY ASSE MBLED 4 5 6A 2 IA B PROBE G R OU N D LEAD ASSEMBLY CONTAI NS 2 2 OHM RESI STOR 456 A 2I A 10 PROBE F L CENTER SECTION COIL SP R I NG TO C3 i FRONT PANEL I I O F I NSTRUMENT LI INTERNAL LOCKWASH E R Figure 4 3 Exploded View of P robe Assembly Section IV Figure 4 3 00395 1 4 5 ...

Page 19: ...T 1101 OPEN leOV K T9 II o 11 0 Y 111 0 f nUIA t1191 r Y IV WK 011 1110 wlff v NOMINAL 11 0 2 J TO ull o RII 2 7 BL f WHT A 860 C90 4OI1F O OI f e5 O OI F e6 10UF R7 3300 AC POWER SUPPLY Rn 90 10K 40 IIf R93 6100 c 1 Q Q90 2N650 REGUL ATOR 131 BATTERY SUPPLY IIC IJLATC D r o 811 lIT 1 T lIT 2 f oOV BTl C O S 4V n 14 R IZ 100 U1 Figure 4 4 Model 456A AC Current Probe R9 ICO e93 lOll RIO 100 RI lao ...

Page 20: ......

Page 21: ... 3 O R DERI N G IN FORMAT I O N To order a replacement pa rt address order or in quiry either to your authorized sales office or to CUSTOMER SERVICE Hewlett Packard Company 395 Page Mill Road Palo Alto California or in Western Europe to Hewlett Packard S A Rue d u Vieux Billa rd No 1 Geneva Switzerland Specify the following information on a part 1 Model and serial number of the instrument Be s u r...

Page 22: ...Diode germanium IN38A Diode silicon Connector female red Connector female black Connector male output Not assigned Cable power Transistor 2N1 516 0C1 70 ot assigned rransistor 2N6 50 esistor fixed composition 24 ohms 5 1 W esistor fixed composition 22 ohms Part of Probe Ground Lead Assembly Component not separately replaceable Mfr 1 Stock No 9 609 5 01 50 0008 5 6289 0 180 0050 5 62 89 0180 0061 5...

Page 23: ...igned Resistor fixed composition 1 5 000 ohms 10 2 W Resistor fixed composition 680 oluns 10 1 2 W Resistor fixed composition 10 000 ohms 1 0 1 2 W Resistor fixed composition 6800 oluns 10 1 2 W Resistor fixed deposited carbon 4000 ohms 1 1 2 W Resistor fixed depOSited carbon 2 2 50 0luns 1 1 2 W Switch slide DPDT Not assigned Transformer powe r Section V Replaceable Parts Sheet 3 of 4 Mfr J Stock...

Page 24: ...onnec tor male Can shield Boot cable Spacer standoff Lead probe ground includ e s R 5 Replaceable Parts Sheet 4 o f 4 Mfr 2 8480 2 8480 2 8480 i 99109 24655 24655 28480 28480 00866 28480 I F Stock No G 64B G 64C 8520 0017 456A 16A 8 120 0048 1 2 50 009 1 1 250 0092 4 56A 55A 4 12A 8 3A 0380 0048 4 56A 2 IA J rQ R S 1 0 1 0 1 0 1 1 1 0 1 0 1 0 1 0 1 0 1 0 1 1 See introduction to this section Model ...

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