HEWLETT PACKARD (HP) 405C
Service Manual

Model 405C
4-7 N E U T R A L I Z I N G THE AMPLIFIER 1) Remove bottom dust cover.

Sect.IV Page 3 When lubricating the stepping switch, it is important to apply the right amount of lubricant. Too much can be as bad as not enough. To a s s u r e the proper amount, the t e r m "dip" will be used as a guide. To obtain one "dip" of lubricant, dip the brush into the lubricant, then wipe the brush against the side of the bottle to remove the drop that f o r m s at the end of the brush. In most c a s e s one dip will be enough t o lubricate several parts. Brush the lubricant lightly over the parts. Do not scrub the brush on the parts because such action usually r e s u l t s in too much lubricant on the f i r s t part and too little on the . others During manufacture the undercut portion of the wiper shaft is filled with ANG-3-A grease, and a small portion of this g r e a s e is applied t o the end of the shaft opposite the mounting hub before the shaft is assembled into the hub. This lubrication is good f o r the life of the switch and needs replacing only when the wiper assembly is replaced.

2) Set line voltage to 115 volts. turn instrument on, and allow 5-minutes warm up.
3) Set RANGE switch to AUTOand SAMPLING cont r o l t o maximum but not t o EXT. 4) Connect direct short a c r o s s 405C INPUT.

+. 000.

5) Adjust Amp Neut control C10 to set readout to This control is mounted on socket of V3.

4-a ~ O S A - ~ S C ADAPTER ADJUSTMENT The only adjustment required by the 405A-95C Digital Recorder Adapter is the adjustment of the s t a i r c s e voltages Recorder. Proceed on the @ Model a560A Digital f o r range indication as follows:
1) Connect Adapter to Recorder only and t u r n Recorder on.

A. EXPOSING THE SWITCH FOR LUBRICATION
1) Remove stepping switch cover. See Figure 4-4.

2) Adjust R302 (A) and R308 (B) in Adapter until voltages at pins 1 and 4 of P301A are +169 and -1-119 respectively. Use the 405C t o measure the set as close as posvoltages, f o r they should be sible to their c o r r e c t values.

2) Remove nuts that hold stepping switch mounting bracket to deck.
3) Remove screws holding switch t o bracket and remove bracket. 4) Lift switch up through deck. You may have to remove relay K2 to make room. Reverse procedure to replace switch. B. LUBRICATING THE STEPPING SWITCH The lubricating points for the stepping switch are shown in Figure 4-1.
4-10 TUBE A N D DIODE REPLACEMENT

4-9 STEPPING SWITCH M A I N T E N A N C E

The stepping switch should be kept clean and well lubricated. Inspect the switch according to the schedule below and add lubricant o r clean and relubricate as necessary.

1) After 30,000 revolutions o r t h r e e months, whichever is first.
2) After each additional 150, 000 revolutions o r six months, whichever is more frequent.

A.

TUBE REPLACEMENT

To obtain the best r e s u l t s from 'maintenance lubrication, first wipe the p a r t s as clean as possible. If the switch is excessively dirty, clean it with a as xylene which does not high-quality cleaner such leave a film upon evaporation.
A lubrication kit consisting of t h r e e types of lubricant, each in a s m a l l bottle, is included with your instrument. Each bottle has a geometric figure (and the switch manufacturer's specification number) on it for easy identification in the lubrication procedure below. Each bottle cap has attached to it the type of brush best suited f o r the particular lubricant. 00518- 1

In many c a s e s of instrument malfunction, the cause is a weak o r defective tube. Locate the as nearly as possible and'check the tubes trouble in the suspected circuits. The best tube checker is the circuit in which a tube must operate. Check tubes by substitution and replace the original one if a newone does not r e s t o r e proper circuit operation. However, if circuit condition (burned resistor, etc. ) indicates that the original tube may be shorted o r otherwise mechanically defective, check the tube on a "tube tester" before returning it to the circuit.