HP 5340A Service Manual

Model 5340A
Theory of Operation
4
- 207. The sample rate circuitry consists of A19Q1, AlSUlA, A19U2E, R1, and R2.
R1 and R2
are located off of the pc board on the main chassis. The sample rate circuitry determines the
length of waiting time between measurements. At the end of
a measurement, XAlgPlA(4) goes
low, allowing
A19C1 to be charged through Rl and R2. Sample rate potentiometer R1 varies
the rate of charge on
A19C1. When A19C1 charges sufficiently, Q1 conducts to trigger Schmitt
trigger
U1A. When U1A triggers, U2E(ll) goes low and XAlgPlA(6) goes high.
4
- 208.
Schmitt trigger
U1B generates a reset when the RANGE and RESOLUTION switches are
changed or when RESET pushbutton S2 is pushed. When power
is first turned on, reset is main -
tained as C5 charges, allowing all circuits to stabilize.
4
- 209. U6D and U6C are buffers for the inhibit signal.
The inhibit signal
is low for the phase
lock mode and high for the direct count mode. U6B and U6A provide RANGE switch information
to A21 and A22.
4
- 210.
Digit Counter U4 keeps track of the counted data while it is being serially shifted into the
display. U3C outputs a low
at the seventh data shift.
4
- 211.
For measurements using the phase lock loops,
it is necessary to subtract 20 MHz from the
counted number to compensate for the 20
MHz phase lock loop IF’S This is accomplished by sub -
tracting a “2” from the appropriate column, as determined by the setting of the RESOLUTION
switch.
U7
is a 5 - bit comparator that determines the proper time to subtract a “2” when U7(1) is
low. U7(14) goes high for coincidence. At all other times, U7(14) is low. This subtracts
a “0” thereby leaving the number unchanged.
4 - 212.
A19 INTERFACE B ASSEMBLY
05340 - 60032 (Part of Option 011)
4 - 213. This board provides control signals
necessary for completing and displaying a measurement and establishes interconnection with the
A34 ASCII Bus Communicator.
The logic level on
XA19PlA(D) controls the U1 circuitry to
select either the internal or an external
10 MHz oscillator with Schmitt triggering circuitry UlA,
UlD, R8, and UlC, UlD, R9, respectively. U20E, U20D, L1, L2, and C4 provide isolation and
buffering.
4
- 214.
The sample rate circuitry, which consists of
A19Q1, A19U2A, and A19U14C, determines
the time between measurements.
At the end of a measurement
XAlgPlA(4) goes low, allowing
A19C6 to be charged at a rate determined by R2 and the setting of Sample Rate pot R1. R1 and
R2 are located on the main chassis, not on A19. See Figure 8 - 25 for Rl and R2 connections. When
A19C6 charges sufficiently, A19Q1 conducts to trigger Schmitt trigger A19U2A(6) to a low if
A19U2A(Pins 1 and 2) are high. Scmitt trigger A19U2B is activated when XAlgPlA(7) goes low,
or when
A19C5 is charging when power is first applied to the instrument.
Refer to Figure 8
- 26 for the schematic diagram.
j
-1
4-215. When the unit is operating on the ASCII bus, many signals that indicate switch settings,
etc., that are normally internally supplied, must be replaced with signals off the bus. U23 is
a
four - pole two position switch that selects resolution information from either the front panel
switch or from U24.
U24
recognizes ASCII codes zero through six.
4
- 216.
U17 is also a four
- pole two position switch that selects range information from either the,
front panel switch or from
U18.
When UlS(9) is activated, U18 accepts range information by
recognizing ASCII characters
“S”, “T”, “U”, or “P”. U19, which recognizes ASCII characters
“F”, and “G”, stores ASCII data that restricts the sweep circuits of the
5340A to a certain frequency range. The ASCII codes and frequency ranges are listed in
Table
2-3.
4 - 217. U25 is a ROM that converts the information on five of the seven ASCII lines to the
required binary code to accbmplish the desired function.
4
- 218. U22A decodes an “/OUTPUT” command and U22B controls the SAMPLE RATE when the
counter is in remote operation. During remote operation, these two circuits are switched on by a
section of U17 and U23, respectively.
U24 stores the information from the bus when
U24(9) is clocked.
‘<A>>, <‘B>?, C<C>F, “D”, “E”,
I,
i
4 - 45

HP 5340A Specifications

General

Brand	HP
Model	5340A
Category	Cash Counter
Language	English