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G8MNY  > TECH     10.02.19 10:30l 75 Lines 3256 Bytes #4 (0) @ WW
BID : 58642_GB7CIP
Read: GUEST
Subj: BNOS 12A 13.8V PSU
Path: ED1ZAC<ED1ZAC<GB7CIP
Sent: 190210/0929Z @:GB7CIP.#32.GBR.EURO #:58642 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                              (New Dec 12)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

I have repaired some these, the 12A (15A meter) & 30A model are similar.
旼컴컴컴컴컴
  旼컴컴      Current limiting
  \          Over voltage Crowbar @ 14.5V
   \     
  읕컴컴  
           
   o   o   
읓쩡컴컴컫쩡

INPUT CIRCUIT
The mains transformer's 2 secondaries feed a bridge rectifier & then to the
capacitor bank. (the bridge can fail on heavy use)
              __          ___________________
L훟-o컴o\커||(  \__      /  +     +        +20V
  3A      )||(_ /  Single  ===  + ===
          )|| _X   Bridge     ===  3x
          )||(  \_Rectifier       6m8
N컴컴컴컴켸||(__/  \     \________________-Ve (0V)
E컴   2x 17V 10A \ \
                   \ 윱>쳐쨈>쳐180컫컴컫컴컫+24V
                    \AC           + __  퀅1
                     읕늘켸       === /_\'===  ON PCB
                          +           24V
                                   읕컴좔컴좔0V
CONTROL CIRCUIT
         +20V쩡컴컴컴컴쩡컴컫컴컴컴컴컴쩡컴컴커
                    /             /     /  2x
       旼쩡컴)컴컫컴캑TIP120    旼컴탠컴쩡캑   2N3055
                 \e  /        \e   \e PASS
             __    읕캑      쳐늘컴 윱쳐캑TRANSISTORS
          __ \_/       \e               R
          /_\    Driver  읕컴캑 旼1k좔훀컴컨컴컴컴컴컴컴컴컴(Amp)컫>+13.8V
              쳐컴컴컴컴컴컴컴))컴컴컴컴컴컴컴컴컴2k2컴        
           쳐컴)컴컴쩡컴컴컴컴))컴컴컫컴컴컴컴컴컫컴컴컴)컴쩡컫컴
                                            __    __ 퀅1  
+24V                 SETI컴)켸               \_/   =\_/  === 
   쳐             /e        5k1캑              red     __ 
  2381          읕큁NP   u1   旼컨컴커8      쳐컴컴캑  1K  /_\
  憫컨컨컨 18k        \      === 쳐퀾C3423쳐 SCR__           
   LM376       \              2읓컫컫쬔     \_/    __     
  읓컫컫컫 SET NPN쳐2k2쩝컴      184납3     /    =\_/     
  4576읓>V   e/    +       1k 쳐+쵬 +100  Green      
   ===윱쵬       === === 10K        === === ===     2k2     
    퀅1    2K2   u1   10u       10u10u u1             
 컴좔좔컴컴컴좔컴좔컴좔컴좔컴좔컴좔컨컴좔컴좔컴좔컴좔좔컴컴컨컴좔컨컴좔>0V
Volt Control     Current Limit      Over Voltage Crowbar

VOLTAGE CONTROL
The voltage control IC LM376 runs on a voltage doubled supply of 24V. It
compares it's internal reference with the preset SET V & drives the TIP120
darlington to drive the 2 heat sinked pass transistors to maintain the output
voltage.

CURRENT LIMITING
The 2 pass transistors have current equalising emitter resistors (R), & when
one of these is over the base emitter voltage of the PNP, that turns on a NPN 
to override the LM376 drive, to limit the current.

OVER VOLTAGE PROTECTION
IC MC3423 is a triggered over voltage IC that fires the crowbar SCR to short
the output if it is too high. Danger here is when charging batteries if the
trip should go causing a fire. So use a fuse with battery!


Why don't U send an interesting bul?

73 De John, G8MNY @ GB7CIP


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