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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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