• Systron Donner 115 Pulse Gen

    From G8MNY@21:5/101 to TECH on Tue Jul 23 09:30:40 2019
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    From: G8MNY@GB7CIP.#32.GBR.EURO
    To : TECH@WW

    By G8MNY (New Jul 13)
    (8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

    I bought one of these pulse generators at a rally (it matched my RF sig gen). It is a 19" 2U rack unit with yellow panels & side carrying handles.

    FRONT PANEL
    RATE DELAY WIDTH + Out Levels - Out
    ___________________________________________________________________
    │ ┌───────────────────────────────────────────────────────────────┐ │
    │ │ ( ) ▀▀ ▀▀ ( ) │ │
    │ │ (O) (O) (O) ▀▀ ▀▀ │ │
    │ │ ▀▀ ▀▀ │ │
    │ │ [ ▄] [▄ ] [ ▄] ( ) ▀▀ ▀▀ ( ) │ │
    │ │----------------------------------------------▀▀-----▀▀--------│ │
    │ │ (·) 0 (·) (·) ø o ø (·) ø (·) ø │ │
    │ └───────────────────────────────────────────────────────────────┘ │
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Ext Enable Sync Power Base + Comp - Base
    In In Out Gnd Out Out Gnd

    SPECIFICATION
    It generates signals from 0.5Hz - 50MHz, 8 decade variable timebase RATE.

    Pulse Delays & Pulse Widths from 100nS - 5S, 8 decade variable.
    As well as fixed ratio square wave (to 25MHz).

    It has 3 main controls, RATE, DELAY, & WIDTH.

    There are 2 inputs for triggering & pulse enable.

    There is a 50Ω 2V pulse sync output for locking up to the start of the
    pulse/delay.

    The two BNC 50Ω outputs give +/- pulses & can be switched to complementary
    (invert pulse sense). The outputs have switched & variable high power output
    attenuators (2W) to give 5V, 2V, 1V, & 0.5V terminated, as well as optional DC
    offset +1 to - 5V. (e.g. offset the 0 & -5V pulse to +5V & 0V)

    PULSE SHAPES
    Single Pulse Mode Double Pulse Mode
    Sync Pulses at +2v
    Repeat RATE ___│___________│___________0v ___│_____________│_________

    DELAY time │───│ │───│ │───│ │───│

    WIDTH time │─│ │─│ ││ ││ ││ ││
    ┌─┐ ┌─┐+5V ┌┐ ┌┐ ┌┐ ┌┐
    +ve Pulse ______│ │_________│ │_0v __││__││________││__││___

    -ve Pulse ──────┐ ┌─────────┐ ┌─0v ──┐┌──┐┌────────┐┌──┐┌───
    │_│ │_│-5v ││ ││ ││ ││

    INSIDE
    There are 2 large PCBs filling the whole unit, one has the PSU for 3 power rails 5V & ±15V & all the pulse generator electronics.

    heatsink
    ____▐▐▐▐▐▐▐▐▐▐▐▐▐▐▐▐▐▐▐________.-----._
    │ +5V +15V -15V | DC -*│ Trans- │
    │ V* | corr- │ former │
    │(·)() () () |ection │_________│ V* = set +15V
    │ P S U | bias │ '-----' │ -* = set -ve pulse -5V ref
    │ | amps ~~~~~~~~~│ 0* = set -ve pulse 0V height
    │ | +* 0* │ +* = set +ve pulse 5V height
    │ Pulse Generators | +ve -ve │ F* = set Max rep frequency
    │ | Pulse Pulse │ D* = set shortest delay time
    │ F* D* W* | amp amp │ W* = set shortest width time
    │ [ ] [ ] [ ] | │
    │ ─┼─ ─┼─ ─┼─ | -load +load │
    │ _│_ _│_ _│_ | DC amp DC amp │ └──┼────┼────┼──────────────────────────┘

    The 2nd PCB has a very complex pair of current limited output amps using 16 heatsinked HF pulse transistors & 5 DC correction op-amps for each of the two 50Ω outputs.

    USES
    Scope calibration of attenuators as the pulse shapes have very wide bandwidth. Coax cable testing, & demonstrating pulse shape-spectrum on spectrum analyser, clearly shows why digital QRM is so bad!

    FAULTS
    Initially it all appears to be working, although a main soothing capacitor had been poorly replaced. Systron Donner kit often fails with main smoothing going open circuit (been there done that!)

    The -ve output occasionally has a DC fault, eventually proved to bad PCB soldered link throughs, on the complex variable/floating output amp biasing.


    See my buls on "A Versatile Pulse Tester", "Spectrum Harmonic Demo circuit". "Variable RF Attenuator" & "Systron Donner 1702 SIG Gen".


    Why don't U send an interesting bul?

    73 De John, G8MNY @ GB7CIP


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