Heathkit IO 4235 Manual

Page 1

HEATH COMPANY o BENTON HARBOR, MICHIGAN

Page 10

Page 8

CONTROL FUNCTIONS

Refer to Pictorial t-I [Illustration Booklet. Page 1] as
you read the following explanations ot'the major con-
trols and switches.

l.

INTENSITY - Clockwise rotation increases the
brightness of the display. Adiust for nominal
brightness in your room-lighting tJlJIttlIllutt. Re-
lncusing may he necessary when the intensity is
changed. CAUTION: Do not allow a bright spot
to remain on the screen. it could damage the
CRT.

FOCUS - Varies the size of the beam striking
the face of the CRT. Adjust for the sharpest dis-

play.
ON-OI-I a Turns the Oscilloscope on nml ol'l'.

POWER INDICATOR Glows when AC power
is turned on.

CHANNEL Y1 CONTR 01.8

5.

10.

Y1 POSi't'iON 7 Positions the channel Y1 trace
vertically on the screen.

DC BAL This is not an operating control. Use
it as directed in the DC. BALANCE section
(Page '11) of this Manual.

PM. TO INVERT - When pulled out. the Y1
trace will be inverted.

Y1 INPI IT-'Ihis isthe Y1 input connector. it is
also the X input connector (1 mi Hg XY operation.

VOL'i'S/CM 7 Each position oi this attenuator
switch is marked tor the number of volts [peak-
llkptfilkl required to produce a pattern one can-
timeter high on the griiticule.

VARIAULIL' - This control is normally operated
in its fully clockwise [(IALI position where the
VOLTS/CM switch positions are calihrated. Ver-
tical gain decreases as the control is turned
counterclockwise. permitting you to adjust the
vertical trace size.

'11.

AC-GNt)-DC [Input switch] - In the At} posi-
tion. this switch hlocksthe DC level ofthe input
signal so that only the AC component is dis-
played. to the END position. the input is dis-
connected and lIIt-t vertical amplifier input is
grounded. Use this position when you wisli to
set the baseline [trace] at a desired position
WIIIItIIII disconnecting the input signal. In the
Ut. position. both the DC and AC components at
the input signal are displayed.

BOTH CHANNELS

'12.

VER'I'ICAL DISPLAY In the Y1 position. only
channel Y1 is displayed on the screen. In the Y2
position. only channel Y2 is displayed. In the
CI IUP positionboth Y1 and Y2 are displayed in
the CHOP mode. in the ALT (alternate) position.
Y1 and Y2 are displayed alternately at the end of
each trace. In the ADD position. the algebraic
summation of channels Y1 and Y2 is displayed.

CH A N NHI. Y2 CONTROLS

'l.'I.

14.

15.

Hi.

17.

'18.

Y2 POSITION - Positions the channel Y2 trace
vertically on the screen.

DC FtAI. -This is not an operating control. Use
it as directed in the DC BALANCE" section of
this Manual.

PULL 'I'U INVERT
[race will be inverted.

When pulled out, the Y2

VOLTSICM -- Each position of this attenuator
switch is marked for the number of volts [peak-
to-peak] required to produce a pattern one cell-
tiineter high on the graticule.

VARIABLE This control is normally operated
in its hilly clockwise (CAL) position where the
VOLTS/CM switch positions are calibrated. Vor-
Iical gain decreases as the control is turned
counterclockwise, permitting the vertical trace
size to be adjusted.

AC-CND-DC [Input Switch) - In the, AC posi-
tion. this switch blocks the DC level of the input
signal so that only the. AC Culiipuuent is dis-
played. ln the ON!) position. the input is dis-

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forms the fast path around the oscillatorsection. This
unhlanks the CRT immediately and then the oscil-
lator can followand hold the tube on lnthe level sctby
the Intensity control until a blanking pulse is applied
In the input. Then the output of the first section ofthe
blanking arnplil'ier will go low. and this will decrease
the level of the oscillator output and blank the CRT.

As shown in Part A' by '8' ol the Piclnrial. in the A
[NTEN BY 8 mode. both the A and U sweep signals
and their separate blanking signals are shown. Only
the A ramp is used but both blanking signals are
summed by 0901: they appear as the A" + B"
unblank signal. The B portion of the trace is inten-
sified as shown at the bottom of the Pictorial. tn the B
DELAYED mode. the B ramp is used for the sweep.

eaI-IEATHKIT

The R ramp is delayed and starts at a selected time
[Td] after the A ramp starts.

Circuits on the horizontal board (U709) route the 'l'l
blanking signalstotheA'blanking output duringthc
B DELAYED mode. This corrects for brightness lost
because the tube is blanked during the A' ramp and
ottly turned on during the B' ramp. This creates a
lower on-to-off ratio and a dimmer trace. Using the B
Ends A control also increases this lost brightness by
decreasing the off time of the lube.

Two other signals are available to the input ot the
blanking amplifier and are summed the same way as
the 'A and B' blanking signals. These are the chop
blank input and the external Z-axis input.

POWER SUPPLY

LOW VOLTAGE POWER SUPPLY

Line voltage enters the scope through fuse F1 and
switch SW1 tn the primary of transformer T1 . Switch
SW2 puts the primary coils on '1] either in parallel for
tZO-volt operation or in series for 240»volt operation.
SW3 selects whether the high or low voltage tap on
the primary is used. The 0.3 volt secondary of trans-
former '1l powers the CRT filament. Another secon-
dary tap supplies the high voltages for the high volt-
age oscillator. the deflection circuits. and other CRT
bias circuits. Diodes D104 and D101 together make a
full-wave rectifier and filtering is supplied by
capacitor ("Juli/t R1t15conples voltage to the high
voltage oscillator circuits and C102 filters the voltage
to reduce the 120 hertz ripple. R101 adjusts the volt-
age to the geometry control grid of the CRT. C101 is a
simple bypass capacitor. The voltage from C103A is
applied through R106 to C1033 for further filtering.
This voltage [approximately 130 volts] powers the
horizontal deflection amplifier circuits. Then R107
further reduces this voltage to power the blanking
circuit, Another rectifier and filter circuit [D102.
D103, C1036. C106.R108.and C104) supplies voltage
to regulator transistor 0101 to produce constant volt»
age for the vertical deflection circuits. R111 supplies
current to zener diodes D113 and D114. They set the
Voltage at the base ot'Q101 to approximately 92 volts.
Since the emitter follows the base, its output is about

six tenths below the voltage at the cathode of D113.
This produces a regulated voltage for the vertical
deflection circuits. R109 limits the dissipation of
transistor Q11 and C105 keeps the circuit stable.

The next secondary on the transformer is connected
to diodes D1115. 11106. D107 and D108.'l'l1is makes a
positive and negative fullvwovc rectifier system.

The AC output of the secondary voltage powers the
pilot light (through P104 pin 2) and is also applied to
R112 and C113 to supply voltage for the line trigger
signal. The RC network filters the 60 cycle signal for
more reliable line triggering. The rectifier output
(from DlOS-DIOB) is filtered by C107 and Ct 14 and
C103 and C109. These voltages are. applied to reg-
ulators U101 and U'IUZ. Resistors R113. R114 and
R115 make up a bias arrangement to set the regulators
to track at +15 and -- 15 volts. C111 and C1 12 provide
output filtering and prevent oscillation.

The third secondary connects to diodes 0100.1J1'10.
D111.and D1 12.I'he output istiltered by C115, C116,
C117. C118. and applied to U103 and 111114. 11103
maintains a 5-volt regulated output. and R110 and
R117 set the regulation voltage of U104 to minus
5,2-volts DC. C119 and (5121 further filter the voltage
coming out ot'the +5-volt and 5-volt regulators and
suppress any oscillations.