English translation
Construction and Explanations of the Analog Computer Type 38500
This is an English translation of the original German-language document: “Aufbau und Inhaltsbeschreibung des Analogrechners Typ 38500” by PEK Electronic, December 1971.
Construction and Description of the Analog Computer Type 38500
The boards are DIN A 3 size and constructed as two-sided boards (Eurocards). The setup with the fold-out housing provides assembly for both demonstration purposes and for regular operation. The left and right halves are not identical — left is labeled “links” (left half), right is labeled “rechts” (right half).
Typ 34211 — Assembly and demonstration board for analog computers, left half
Typ 34212 — Assembly and demonstration board for analog computers, right half
Typ 3413 — Assembly rack, right half
In the right cabinet are the actual computing boards (Rechenplatten) 38500 to 38508, the signal generation 38509, and the power supply 38507/88. Also in the left cabinet are the Steuerplatten (control boards) type …
The analog computer is assembled as shown in the next figure.
Assembly of the Analog Computer
It is advisable to always handle the boards with the fold-out housing during demonstrations and exercises, because the two free assembly boards (38505 and …) allow additional function units to be plugged in.
December 1971 — L 1356 – s.1
Boards Used in the Analog Computer
The analog computer type PEK 38500 uses 10 working boards, which also include additional boards (Hilfsplatten).
38500 Potentiometers
On this board are 15 potentiometers arranged, with different switches:
- 3 units for input (Anfangswert): Apply fixed +15 V when switched
- Code Fest on (Anfang) when switched
- Code Fest on Mass when switched
- Code free programmable (frei programmierbar)
- 6 switches completely free (völlig frei programmierbar)
(Diagram showing potentiometer symbols with various configurations)
38501 Summierer I (Summing Amplifiers I)
On this board are 6 summing amplifiers (Summierer), 4 of which have fixed amplification and 2 are equipped with a pluggable feedback resistor.
The summing point (node 6, input 1) is reversed from the normal direction.
The summing amplifier circuit has 2 inputs with amplification 1, and 2 inputs with amplification 10. The feedback resistor can be changed, so amplification can be varied — resulting in Hochverstärkung (high amplification).
December 1971 — L 1355.1 – S.2
38504 Summierer II (Summing Amplifiers II)
This board is identical to board 38502. It also contains 6 summing amplifiers, where 4 have fixed amplification and 2 are equipped with a pluggable feedback resistor.
Summierer (38502 and 38504)
(Diagrams showing summing amplifier configurations with inputs U₁ through U₅, and gain settings of 1 and 10)
On the Summierer board 38504, an additional assembly group is housed, which can be designated as a Z-jump (Z-Sprung). This assembly can be connected to the output of a summing amplifier (see A 1351).
December 1971 — L 1351.1 – S.2
38503 Integrierer (Integrators)
There are 4 integrators; three integrators have 5 inputs and one has 2 inputs.
Each integrator is equipped with a fixed feedback capacitor and a pluggable initial condition resistor. The resistance of these inputs is constantly variable, and the integrator allows for step variation in the number of inputs.
Before all inputs are separated, an “Anfangsbedingung” (initial condition relay) is placed, so that it can be set to an “Anfangsbedingung” (initial condition). These relays are designed in the form of printed circuit boards (Relais), and can be set to “Festnebst” (closed/latched).
(Diagram showing integrator symbols with relay inputs)
December 1971 — L 1351.1 – S.3
38505 Potenzial-Multiplizierer (Potential Multipliers)
There are two equally designed multiplier boards (Potenzial-Multiplizierer). For the multiplication, each negative value must be inverted at the corresponding input. The multiplier thus has 4 networks per output, whose amplification is 4. The output has a digital-to-analog converter.
Potenzial-Multiplizierer
(Diagram showing multiplier circuit symbol)
38506 Programmierfeld (Programming Field)
The programming field is assembled with push-in connectors (mit Griffen versehen), which allow the same persons to use the analog computer more conveniently. All inputs and outputs of the individual boards are accessible on the programming field. The individual plugs connect various circuit elements.
December 1971 — L 1351.1 – S.4
38507 Servomultiplizierer (Servo Multiplier)
The second servo multiplier is identically constructed. On the motor-driven axis is also located an offset for the Sinus and Cosinus of the Referenzspannung.
Torus-Multiplizierer
(Diagram showing torus multiplier circuit)
38508 Meßwertanzeige (Measured Value Display)
To display output values statically, the Meßwertanzeige (measured-value display) board is provided. The board is built in immediately. This board also includes a digital measuring instrument for commercial use.
Meßinstrument
(Diagram showing meter display)
38509 Bedienungs- und Steuerplatte (Operating and Control Board)
This board fulfills several functions. The Farbcodierung (color coding) of the programmed computer couplings gives an overview of the die vorhandene (existing) Schaltverbindungen. It also provides an automatic controller with single switching of the Vorgangswert, also a negative output, +50 V. Hold voltages simultaneously supply the machine with 100 V reference voltage.
December 1971 — L 1351.1 – S.5
The other function of the board is the connection to other peripheral devices, especially to an X-Y plotter or oscilloscope, or data display.
36013/A3 Netzanschluß (Power Supply)
Two power supply units are housed here, which are independent of each other. Each voltage is adjustable to 6 V, 12 V, and 15 V. For the operation of the analog computer, only voltages of +15 V and −15 V are required. The power supplies maintain constant voltage and are short-circuit protected.
December 1971 — L 1351.1 – S.6