English translation
Dual-Beam Oscilloscope OMS 811
This document is an English translation of the original German-language manual “Zweistrahloszillograph OMS 811” (Section 10 / Abschnitt 10), Telefunken.
Table of Contents
| Section | Title | Page |
|---|---|---|
| 10. | Dual-Beam Oscilloscope OMS 811 | 10-1 |
| 10.1. | Intended Use | 10-1 |
| 10.2. | Mode of Operation | 10-1 |
| 10.3. | Construction and Components | 10-3 |
| 10.3.1. | Mechanical Construction | 10-3 |
| 10.3.2. | Component Population | 10-3 |
| 10.4. | Electrical Concept | 10-5 |
| 10.4.1. | Power Supply | 10-5 |
| 10.4.2. | High-Voltage Generation | 10-6 |
| 10.4.3. | Filter Plug-In Unit SB1A | 10-8 |
| 10.4.4. | Input Amplifier | 10-8 |
| 10.4.5. | Compensation Circuit | 10-8 |
| 10.4.6. | Electronic Switch SP2A | 10-8 |
| 10.4.7. | Sawtooth Plug-In Unit A-KM1 | 10-9 |
| 10.4.8. | Direct Brightness Control for Single-Channel Operation | 10-9 |
| 10.4.9. | Deflection Amplifiers | 10-10 |
| 10.4.10. | Display Tube | 10-10 |
| 10.5. | Maintenance and Repair | 10-11 |
List of Figures:
- Figure 10.3.1: Dual-Beam Oscilloscope OMS 811 as Slide-In Unit — 10-3
- Figure 10.4.2: Oscillator and High-Voltage Section — 10-7
List of Referenced Drawing Numbers
Summary of referenced documents for the Dual-Beam Oscilloscope OMS 811 description and maintenance:
| Drawing No. | Description |
|---|---|
| 55.3007.100-00 | OMS 811 (overall) |
| 55.3007.026-00 | High-voltage section |
| 55.3007.108-00 | Circuit board 1 |
| 55.3007.109-00 | Circuit board 2 |
| 55.3005.059-00 | SP2A |
| 55.3005.060-00 | SB1A |
| 55.3005.521-00 | H-GR1 |
| 55.3005.524-00 | H-KS1 |
| 55.3040.876-00 | A-KM1 |
| 55.3040.890-00 | A-SV1A |
10. Dual-Beam Oscilloscope OMS 811
10.1. Intended Use
The oscilloscope OMS 811 is used for display and evaluation of analog computer output voltages. It can display voltages in the range of 100 V in real-time and can be operated as a recorder (slow speed). When used in this mode, it records frequency-less analog signals. The OMS 811 can display two channels simultaneously as shown in Figure 10.3.1.
10.2. Mode of Operation
The oscilloscope OMS 811 is equipped with three input channels X1, X2, Y1, and Y2. While positive inputs of the channels are referenced to the preamplifier inputs (Vorverstärker-Eingänge), the deflection is carried out with a differential amplifier. The preamplifier simultaneously amplifies the signal by a factor of approximately 4:1 to 5:1. Negative feedback linearizes and limits bandwidth.
A sawtooth signal is generated in the device from either an external signal (from 100 kHz timebase frequency 0.1 Hz/multiplex) or internally from the 100 kHz system clock (100 kHz/n) or from Digital-Program-Multiplexer (DPM). As given by the individual channels H0 or H1, the deflection frequency can range from 0.1 Hz to approximately 60 Hz.
The analog (oscilloscope channel) allows direct linkage to the control panel “Bedienpult” via connection head or to the recorder. The oscilloscope amplifier has a bandwidth of 10 Hz; a multi-channel recorder (DAT) can also be used.
Analog Operation (a): At the measurement input of the recorder, it is possible to connect up to 5 inputs of X1 with simultaneous deflection of the same time base. It is possible to switch from “Einzel” (single) to “b Mehrfach” (multiple).
10.3. Construction and Components
10.3.1. Mechanical Construction
The OMS 811 is built as a slide-in unit (Einschub) for use in a 19-inch rack (Einschubgehäuse RA 175). The unit was developed for its own chassis based on drawing 19 B.1; the oscilloscope tube is enclosed in its own casing. The slide-in unit dimensions (width × height × depth in mm): approximately 482 × 177 × 370 (19 RU). The unit can be swiveled at the front on hinges (Bu 18.1) so that the front panel can be swung forward by approximately 180° to allow access to the circuitry. The unit weighs approximately 13 kg.
10.3.2. Component Population
For convenient servicing, the OMS 811 has a number of plug-in assemblies and components:
| Qty | Description | Designation | Part No. |
|---|---|---|---|
| 4 | Amplifier plug-in units | A-SV1A | 55.3040.890-00 |
| 2 | DC voltage regulator plug-in units | H-GR1 | 55.3005.521-00 |
| 1 | Cooling plug-in unit | H-KS1 | 55.3005.524-00 |
| 2 | Switch plug-in units | SP2A | 55.3005.059-00 |
| 1 | Filter plug-in unit | SB1A | 55.3005.060-00 |
| 1 | Sawtooth plug-in unit | A-KM1 | 55.3040.876-00 |
| 2 | Amplifier tubes | ECC801S | — |
| 1 | Oscilloscope tube | DN13-14 | — |
| 2 | Small lamps | 6V 0.1A | — |
| 1 | Fuse | T 0.315 | — |
The plug-in units are assigned to the magazine sockets (Magazinbuchsen) as follows:
| Unit | Socket |
|---|---|
| A-SV1A | Bu 6 |
| A-SV1A | Bu 7 |
| A-SV1A | Bu 8 |
| A-SV1A | Bu 9 |
| H-GR1 | Bu 17 |
| H-KS1 | Bu 18 |
| H-GR1 | Bu 16 |
| SP2A | Bu 10 |
| SP2A | Bu 11 |
| SB1A | Bu 15 |
| A-KM1 | Bu 14 |
10.4. Electrical Concept
10.4.1. Power Supply
The various supply voltages in the oscilloscope are derived from the mains transformer. Voltages and their purposes:
| Voltage | Purpose |
|---|---|
| +175 V / 6.3% | Compensation voltage, screen voltage |
| +175 V / 6.3% | Cr10, Cr16 |
| -167 V / ±0.06% | Transistor DC supply voltage |
| ≈100 V | Cathode-ray tube (CRT) supply |
| -220 V | Deflection amplifier supply voltage |
| Winding: 6.3V 9A / 6 winding sections, 18-20 | Heating voltage for tubes, lamps, etc. |
The mains transformer provides a voltage somewhat above the (network) supply for the cathode-ray tube filament. Regulated circuits include the DC rectifier (Gleichrichter) Tu2 as rectifier; the rectifier forms the DC voltage for ±12/18 V. The transformer Tu2 is connected to the mains through fuse T 0.315 A.
The intermediate circuit provides a voltage:
- Winding 10-11-12 delivers (depending on network Tr2) the AC mains voltage
- Various filter circuits stabilize the supply
10.4.2. High-Voltage Generation
The high-voltage generation circuit uses a 100 kHz oscillator based on transistors Ts1 (DW6176). The oscillator works in push-pull configuration. The high-voltage section drawing (Zeichnungs-Nr. 55.3003.921-00) and the circuit board use:
The high-voltage section contains a transistor push-pull oscillator whose primary coil drives transformer Tr2. From secondary windings, the accelerating voltage for the CRT and the screen voltage are derived. The high-voltage section is marked as drawing No. 55.3007.026-00.
(See Figure 10.4.2: Oscillator and High-Voltage Section on page 10-7)
10.4.3. Filter Plug-In Unit SB1A
The filter (Siebsteckeinheit) SB1A, drawing No. 55.3005.060-00, is a voltage smoothing and filtering unit. It is used to suppress noise and ripple in the supply voltages.
10.4.4. Input Amplifier
The input amplifier (Eingangsverstärker) A-SV1A, drawing No. 55.3040.890-00, is a DC-coupled differential amplifier. Inputs require signals of approximately 4:1 amplification factor. Cathode follower Tr1, Tr2 forms the input stage. The bandwidth is limited to 10 Hz for recording purposes. The compensation capacitor C1 to C4 is adjustable for time constant equalization.
10.4.5. Compensation Circuit
The compensation circuit (Kompensationseinrichtung) allows the zero offset and amplification of each channel to be individually trimmed. It enables precision calibration.
10.4.6. Electronic Switch SP2A
Through the electronic switch SP2A, drawing No. 55.3005.059-00, the inputs to channels Y1 and Y2 can be switched. The switch uses two transistors T1 and T2. The linewidth (Linienbreite) is approximately 0.1 mm; this provides accurate dual-channel display.
The switch unit A-KM1 controls the switching between Y1 and Y2. The switching rate is determined by the timebase frequency, enabling alternating (ALT) or chopped (CHOP) display modes.
10.4.7. Sawtooth Plug-In Unit A-KM1
The sawtooth plug-in unit A-KM1 (Kippstufe-Steckeinheit), drawing No. 55.3040.876-00, generates the horizontal deflection sawtooth voltage. It can be triggered externally (from the analog computer timebase at 0.1 Hz to approximately 100 Hz) or internally.
For single-channel operation (Einkanalbetrieb), the brightness control signal is derived directly from the A-KM1 unit. Two resistors R13 and R14 serve as output impedance matching.
10.4.8. Direct Brightness Control for Single-Channel Operation
In single-channel operation mode, the brightness of the electron beam is controlled directly through the A-KM1 sawtooth unit. This avoids the need for an external blanking signal and allows simple display without the electronic switch SP2A.
The control signal acts upon the grid (G1) of the cathode-ray tube to modulate beam intensity.
10.4.9. Deflection Amplifiers
The deflection amplifiers (Ablenkverstärker) T1 and T2 are DC-coupled push-pull amplifiers for driving the Y-deflection plates of the CRT.
Two resistors R13 and R14 serve as output impedance for each channel. The frequency compensation is applied through capacitors C13 and C34 in parallel. The amplifier bandwidth up to approximately 10 Hz ensures proper recording of slowly changing signals.
After the channel selectors X1 and X2, the Y1 and Y2 amplifiers send the signal to the deflection plates of the display tube.
10.4.10. Display Tube
The display tube (Anzeigeröhre) is type DN13-14, a dual-beam cathode-ray tube. It has two independent electron beam paths (Y1 and Y2) with a shared X-deflection, enabling genuine dual-channel simultaneous display on a single screen.
The tube’s electrodes:
- Cathode
- Control grid G1 (brightness/blanking)
- Screen grid G2
- Focus electrode
- Deflection plates X and Y (for each beam)
The two beams can be independently positioned and scaled. The accelerating voltage for the tube is approximately +2000 V from the high-voltage section.
10.5. Maintenance and Repair
Maintenance of the OMS 811 is only necessary in exceptional cases or at long intervals. However, after longer periods of computer downtime, it is recommended upon start-up of the analog computer to check the zero point and amplification and, if necessary, to readjust using the “0” and “V” controls (see operating manual).
Maintenance tasks that can be carried out by the customer are limited to replacing plug-in units, small lamps, and the fuse. The device must be completely disconnected from the mains for this.
Repair and alignment work on the OMS 811 that require connecting the device to the mains in a partially disassembled state may only be performed by trained maintenance specialists, due to the high-voltage-carrying parts.
[Translation covers all 14 pages of the original document — this is a complete translation of the full manual section.]