![Tektronix 318 Technical Manual Download Page 98](http://html1.mh-extra.com/html/tektronix/318/318_technical-manual_1077905098.webp)
TM 11-6625-3145-14
Theory of Operation-318/338 Service
Assume that A10Q220 is conducting just before TO and that the current 11 is passing through A10Q220. A10Q220 is
turned off at TO by the inverted CHD pulse. The energy stored in L140 and L150 is discharged through A10C230, causing
current 12. Current 12 charges up A10C230 to about + 45 volts at T1. The stored energy in A10C230 is discharged
during the time interval T1 to T2. Discharging current 13 charges L140 and L150, causing the A10Q220 collector voltage
to go negative. When the A10Q220 collector voltage goes negative to more than -5 volts at T2, diode A10CR230
conducts. The stored energy in L140 and L150 is then discharged through A10CR230, and, at the beginning of T3,
through A10Q220. The discharging current decreases to zero at T4. Therefore, L140 and L150 stop discharging and are
charged again in the opposite direction by charging current I1.
Current I1 increases until A10Q220 is turned off again. The A10Q220 collector waveform is shown in Figure 4-13 as the
ideal waveform; the actual waveform may contain more noise. The collector voltage at A10Q220 is applied to the primary
winding of T230. This transformer provides voltages for G1, G2, and the anode input of the CRT. It also provides voltage
for the Z-axis amplifier. A high-voltage multiplier is included in the flyback transformer box.
VERTICAL SWEEP GENERATOR
The vertical sweep generator stage consists of IC A10U001 which produces the sawtooth current for vertical deflection in
yoke L150. The VD (Vertical Drive) signal’s 0.572 ms pulse triggers this circuit every 16.6 ms.
IC A10U001 consists of a triggerable astable multivibrator, sawtooth generator, and output amplifier.
The astable multivibrator’s time-constant is determined by A10R002, A10R005, and A10C005, and locked by the VD pulse
at 16.6 ms. The output signal of the multivibrator generates a sawtooth signal when A10R010, A10R015, A10C010, and
A10C015 charge and discharge. The sawtooth signal is AC-coupled to pin 7 on A10U001. Amplifier A10U001 drives the
vertical deflection yoke L1 50.
318/338 All POWER SUPPLY <15> <16>
The power supply circuit provides the operating power for this instrument from the ac line-voltage source.
Figure 4-14 is a simplified block diagram of the power supply circuit.
LINE INPUT <15>
Power is applied through the line filter FL1, line fuse F1, power switch A12S1, and thermal cutout switch S3. The line filter
is designed to keep power-line interference from entering the instrument and to keep the approximately 50-kHz inverter
signal from entering the power line.
Line voltage selector switch S2 allows the instrument to operate from either a 115 or 230 volt nominal line voltage source.
In the 115V position, rectifier A11CR1 01 operates as a full-wave voltage doubler with energy-storage capacitors A11C121
and A11C122. The voltage across the two capacitors in series is the approximate peak-to-peak value of the 115 volt line.
For 230 volt operation, A11CR101 is connected as a bridge, supplying approximately the peak value of the 230 volt line.
Thus, the dc voltage applied to the inverter stage is about the same for either 115 or 230 volt operation.
4-37
Summary of Contents for 318
Page 119: ...318 VERIFICATION AND ADJUSTMENT PROCEDURES ...
Page 182: ...338 VERIFICATION AND ADJUSTMENT PROCEDURES ...
Page 253: ...318 ___________________ TROUBLESHOOTING TREES ...
Page 344: ...338 TROUBLESHOOTING TREES ...
Page 517: ...TM 11 6625 3145 14 318 338 4434 923 318 Block Diagram ...
Page 518: ...TM 11 6625 3145 14 318 338 4434 924 338 Block Diagram ...
Page 519: ...TM 11 6625 3145 14 318 338 4434 925 318 Acquisition Module Wiring Diagram ...
Page 520: ...TM 11 6625 3145 14 318 338 4434 926 318 338 Mainframe Wiring Diagram ...
Page 521: ...TM 11 6625 3145 14 318 338 4434 926 338 Acquisition Module Wiring Diagram ...
Page 522: ...TM 11 6625 3145 14 318 338 4434 928 Figure 9 1 318 A01 Input A Board Component Locations ...
Page 526: ...TM 11 6625 3145 14 ...
Page 528: ...TM 11 6625 3145 14 Figure 9 3 318 338 A03 ACQ Control Board Component Locations ...
Page 532: ...TM 11 6625 3145 14 ...
Page 536: ...TM 11 6625 3145 14 ...
Page 538: ...TM 11 6625 3145 14 ...
Page 539: ...TM 11 6625 3145 14 ...
Page 540: ...TM 11 6625 3145 14 ...
Page 541: ...TM 11 6625 3145 14 ...
Page 542: ...TM 11 6625 3145 14 Figure 9 8 318 338 A10 CRT Board Component Locations ...
Page 544: ...TM 11 6625 3145 14 Figure 9 9 318 338 A11 Inverter Board component Locations ...
Page 546: ...TM 11 6625 3145 14 Figure 9 10 318 338 A12 Regulator Board Component Locations ...
Page 551: ...TM 11 6625 3145 14 Figure 9 12 338 A01 Input A Board Component Locations ...
Page 553: ...TM 11 6625 3145 14 318 338 SERVICE ...
Page 554: ......
Page 555: ...PIN 058584 ...