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G8MNY  > TECHNI   21.04.22 10:42z 103 Lines 4452 Bytes #6 (0) @ WW
BID : 479_GB7CIP
Subj: Systron Donner 115 Pulse Gen
Sent: 220421/0905Z @:GB7CIP.#32.GBR.EURO #:479 [Caterham Surrey GBR] $:479_GB7C

By G8MNY                                (Updated Aug 20)
(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.

        RATE       DELAY       WIDTH      + Out    Levels   - Out
                                        ( )             ( )  
      (O)         (O)         (O)                            
  [ ]      [ ]     [ ]               ( )             ( )  
  () 0     ()       ()        o          ()    ()       
    Ext     Enable      Sync    Power    Base    +  Comp  -    Base
    In        In        Out              Gnd    Out      Out   Gnd

 It generates signals from 0.5Hz - 25MHz, 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 50 2V pulse sync output for locking up to the start of the

 The two BNC 50 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)

             Single Pulse Mode                   Double Pulse Mode
Sync Pulses at              +2v
Repeat RATE _________________________0v     _________________________
DELAY time     ij       ij                 ij         ij

WIDTH time         ij         ij                           
                   Ŀ         Ŀ+5V            ڿ  ڿ        ڿ  ڿ
+ve Pulse    ______ _________ _0v          _________________

-ve Pulse    Ŀ Ŀ 0v          ĿĿĿĿ
                   _         _-5v                        

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

     +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
50 outputs.

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!

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 +15V rail to the DC load amp, on this 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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