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G8MNY > TECH 15.03.26 18:11l 211 Lines 9594 Bytes #7 (0) @ WW
BID : 54461_GB7CIP
Subj: DRAE 24A 13.5V PSU
Path: JH4XSY<N3HYM<GB7YEW<GB7CIP
Sent: 260315/0903Z @:GB7CIP.#32.GBR.EURO #:54461 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Jan 10)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I have repaired 2 of this series so far, a 12A & a 24A model.
These are complex linear PSUs and use some unusual design features....
Short circuit current fold-back to 10A
Current limit @ 24A
Temperature limit trip
Over voltage limit @ 14V
Over voltage Crowbar @ 14.5V
Negative rail regulation
Earthed 2N3055 collectors
Current copiers extend current to 24A.
BLOCK SCHEMATIC (no diagram hence reverse engineered)
ﾚﾄﾄﾄﾄﾄﾄｿﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄｿﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄｿ
ｳMains ﾃｴ Dual ﾃｴCapacitorﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄ>+13.5V
ｳTrans-ﾃｴ Bridge ﾃｴ Bank ｳ ﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｿ ｳ ｳ
ｳformerｳｳRectifierｳｳ ﾃﾄｿ ｳTemp & I limitﾃﾄ)ﾄﾄｿ ｳ
ﾀﾄﾄﾄﾄﾄﾄﾙﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾙﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾙ ｳ ﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴ ｳ ﾚﾁﾄﾄﾁﾄﾄﾄｿ
ｳ ｳ 6A linear ﾃﾄﾙ ｳ Over ｳ
ﾃﾄｴ reg PSU ﾃﾄｿ ｳVoltageｳ
-veｳ ﾀﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾙ ｳ ｳCrowbarｳ
ｳ ﾚﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾄﾄｿ ｳ ﾀﾄﾄﾄﾂﾄﾄﾄﾙ
ﾃﾄｴCurrent Copierﾃﾄｴ ｳ
(-10V)ｳ ﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴ ｳ ｳ
ﾃﾄｴCurrent Copierﾃﾄｴ ｳ
ｳ ﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴ ｳ ｳ
ﾀﾄｴCurrent Copierﾃﾄﾁﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄ> 0V
ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾙ
INPUT
The huge mains transformer's 2 secondaries each feed a bridge rectifier and
then on to each side of the capacitor bank. The +ve side is the + output in
this design, but it goes through several PCB links!
___ _________________________________
Lﾄo-oﾄﾄo\ﾄﾂﾄﾄｿ||( Rectifier + ｳ ｳC2ｳ ｳC4ｳ ｳC15ｳ ｳ +13.5V
6.3A ｳ )||(__Bridge 1ﾄﾄﾄ)ﾄｿ ｳ === ｳ === ｳ === ｳ
neon )|| ___ __ｳ ｳ === ｳ === ｳ === ｳ ===
ｳ )||( Rectifier + ｳ C1ｳ ｳC3ｳ ｳ ｳC12ｳ ｳC16
Nﾄﾄﾄﾄﾄﾄo\ﾄﾁﾄﾄﾙ||(__Bridge 2_____ｳ___ｳ__ｳ__ｳ__ｳ__ｳ___ｳ__ｳ____-Ve (-10V)
Eﾄﾄｿ 2x 17V 20A
ﾁ
CONTROL CIRCUIT
Three opamps are used in the linear regulator in a cascade set up. IC1B
monitors the temperature and it's output together with a overvoltage sensing
transistor affect the current limiter opamp IC1C. This in turn offsets the
voltage setting pot on the voltage control opamp IC1D to affect the current
limiting.
The voltage reference zener D6 is initially powered via R17 and filter R15 and
cap C8 to delay power up, then from the output (D7 & R6) this gives the reduced
fold-back current on a shorted load, Voltage Opamp IC1C compares this reference
to the output sample from voltage setting pot P4. IC1D operates PNP TR1 to
drive the 2N3055 pass transistor TR2 to deliver up to 6A.
When 6A is reached in TR2, the voltage across R12 is compared to the value from
P2 by IC1C and it's output falls, -ve voltage is feed into P4 to reduce the
voltage and hence limit the current.
When too hot the voltage across D2 (by TR2) exceeds P1 setting and opamp IC1B
output goes high and this feeds IC1C to stop the output.
ﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄ>+13.5V
5ｳ\IC1B ｳ C8ｳ+ ｳ _ｳ_
ﾚﾄﾄｴ+\ 7 R1 IC1D === R13 D6 /_\'
ｳ ｳ >ﾄﾄﾄ)ﾄﾄﾄR9ﾄﾄｿ /ｳ12 ｳ ｳ ｳ
ｳ6ﾚｴ-/ ｳ ｳ From R26 14 /+ﾃﾄﾄﾄﾁﾄﾄﾄ)ﾄﾄﾄR15ﾄﾂﾄﾄﾄｴ
ｳ ｳｳ/ D3 ﾃﾄｿ ﾃﾄ<overV ﾚﾄﾄ< ｳ VOLTS ｳ ｳ
ｳ ﾃﾄR2ﾄｴ<ﾃｴ R3 ｳ ｳ \-ﾃﾄﾄﾂﾄﾄ>POT R17 ｳ
ｳ ｳ ﾚﾄﾄﾄ)ﾄﾁﾄｿ ｳ IC1C ｳC9 \ｳ13ｳ P4 ｳ _ｳ_
ｳ ｳ T ｳ I ｳ10ｳ\ ﾃﾄｴﾃﾄﾄﾄﾄﾄﾙ ｳ Startｳ \_/D7
ﾀﾄ)ﾄﾄ>POT ｳ POT<ﾄﾄ)ﾄﾄｴ+\ 8 ｳ D5 ｳ up ｳ ｳ
ｳ P1 ｳ P2 ｳ ｳ >ﾄﾄﾄﾄﾄﾄ)ﾄﾄﾄﾄﾄR5ﾄﾄｴ<ﾃﾄｴ -ve ｳ
ｳ ｳ _ｳ_ ｳ ﾃﾄﾄｴ-/ _ｳ_TR1 ｳ ｳ
ｳ ｳ '/_\ ｳ ｳ 9ｳ/ PNP/ \e 250mA ｳ R6
ｳ ｳ D1ｳ ｳ R8 ﾚﾄﾄﾄﾄｴ ﾀﾄﾂﾄﾄﾄｿ R14 ｳ
_ｳ_D2ｳ ｳ ｳ ｳ R11 _ｳ_ L1 R25 ｳ ｳ
\_/ ｳ ｳ ｳ ｳ ｳ e/ \TR2 ｳ ｳ ｳ ｳ
ﾄﾄﾁﾄﾄﾄﾁﾄﾄﾄﾁﾄﾄﾂﾁR12ﾁﾂﾄﾄﾄﾄﾁﾂﾄﾙ ﾃﾄﾄﾄﾁﾂﾄﾄﾁﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾁﾂﾄ>0V
-ve ｳ ｳ ﾀﾄｴ>ﾃﾄｴ6A ｳ ﾁ
ｳ ｳ D8 ﾁ ｳ
\ To Current Copiers /
COMPONENT LIST
No R | No R C TR D P IC TH L
17 1M | 1 3K3 4m7 25V BD131 5.6V 2K2 LM324N BTI51 ?
18 22R | 2 10K 4m7 25V 2N3055 1N4148 2K2 LM324N
19 0R05 2W | 3 6K8 4m7 25V TIP31B 1N4148 220R
20 | 4 2N3055 14V 2K2
21 22R | 5 10K TIP31B 1N4148
22 0R05 2W | 6 3K3 2m2 16V 2N3055 5.6V
23 22R | 7 10n TIP31B 1N4148
24 0R05 2W | 8 1K5 ? 2N3055 1N4001
25 22R | 9 27K 10n
26 3K3 | 10 22R 10W u1
27 27K | 11 22R 2m2 16V
28 3M3 | 12 0R05 2W 4m7 25V
| 13 10K 1n
| 14 15K
| 15 10K 4m7 25V
| 16 3K3 4m7 25V
CURRENT COPIERS
ｳ ｳ 3ｳ\IC1A ｳ
ｳ ﾃﾄﾄﾄｴ+\ 1 ｳ
ｳ ｳ ｳ >ﾄﾄﾄｿTR3ｳ Three more 2N3055
ｳ ｳ ﾚﾄｴ-/ _ｳ_ ｳ each with a driver
ｳ ｳ ｳ4ｳ/ e/ \ ｳ and opamp are used
ｳ ｳ ﾃﾄﾄR18ﾄｴ ﾀﾄｴ to get the current
ｳ ｳ ｳ _ｳ_ ｳ up to 24A.
ｳ ｳ ｳ e/ \TR4 ｳ
ﾃﾄR19ﾄ)ﾄﾁﾄﾄﾄﾄﾙ ﾃﾄﾄﾄｴ
ｳ ｳ 12ｳ\IC2D ﾁ ｳ
ｳ ﾃﾄﾄﾄｴ+\ 14 ｳ
ｳ ｳ 13ｳ >ﾄﾄﾄｿTR5ｳ
ｳ ｳ ﾚﾄｴ-/ _ｳ_ ｳ
ｳ ｳ ｳ ｳ/ e/ \ ｳ
ｳ ｳ ﾃﾄﾄR22ﾄｴ ﾀﾄｴ
ｳ ｳ ｳ _ｳ_ ｳ
ｳ ｳ ｳ e/ \TR6 ｳ
ﾃﾄR22ﾄ)ﾄﾁﾄﾄﾄﾄﾙ ﾃﾄﾄﾄｴ
ｳ ｳ 10ｳ\IC2C ﾁ ｳ
ｳ ﾀﾄﾄﾄｴ+\ 8 ｳ
ｳ ｳ >ﾄﾄﾄｿTR7ｳ
ｳ ﾚﾄｴ-/ _ｳ_ ｳ
ｳ ｳ9ｳ/ e/ \ ｳ
ｳ ﾃﾄﾄR23ﾄｴ ﾀﾄｴ
ｳ ｳ _ｳ_ ｳ
ｳ ｳ e/ \TR8 ｳ
ﾀﾄR24ﾄﾄﾄﾁﾄﾄﾄﾄﾙ ﾃﾄﾄﾄﾙ
ﾁ
PROTECTION
Addition over voltage limiting circuit using TR9 shuts off the drive if output
rises above 14V. If there is no control due to a blown up pass transistor, a
SCR crowbar circuit will short the output as well (no fuse so destroying the
pass transistors?)
Warning due to the SCR crowbar, do not connect an unfused battery!
ﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾂﾄﾄﾂﾄﾄﾄﾂﾄﾄﾂﾄﾄﾂﾄ>+13.5V
_ｳ_ ｳ ｳ ｳ ｳ ｳ ｳ
D4/_\' ｳ ｳ ｳC6 ｳ ｳ ｳ
ﾚﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄｴ FBｳ ｳ === ｳ ｳ ===
e\ｳ === ｳ |ｳ| ｳ ｳ === ｳ ｳu1 on
Over- TR9 ﾃﾄﾂﾄﾄｴC13 ｳ TH1_ｳ_ ｳ ｳC11ｳ ｳ ｳterminals
volts PNP/ｳ ｳ ｳ ｳ \_/ ｳ ｳ ｳ R10 ｳ
to IC1 <ﾄR26ﾄﾙ R28 ｳ TRIP<ﾄﾄﾂﾄ/ｳ === ｳ ｳ ｳ ｳ
pin9 ｳ ｳ P3 ｳ ｳ C10ｳ ｳ ｳ ｳ ｳ
>-veﾄﾄﾙ R27 ｳ C7=== ｳ ｳ ｳ ｳ ｳ ｳ
ﾁﾄﾄﾄﾄﾁﾄﾄﾄﾄﾁﾄﾄﾁﾄﾄﾄﾄﾁﾄﾄﾁﾄﾄﾄﾁﾄﾄﾁﾄﾄﾁﾂﾄ>0V
ﾁ
Several caps are across the output as well as a 7W load of R10, these soak up
any sudden changes in the loading.
STATUS LED Modification
ﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄ>+13.5V
470R ｳ ﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｿ
ﾃﾄﾄﾄﾄｿ === u1 ｳ ﾚﾄｿ ｳ
RED _ｳ_ _ｳ_ GREEN ｳ ｳ ﾀﾄﾙ ｳ
LED _/ \_/� LED ﾃﾄﾄﾄ>0V Red ｳo ｳ
FAIL ｳ _ｳ_ OK ﾁ ｳ (�)+ ｳ
ｳ /_\' Greenｳo ｳ
wireｳ ｳ 9V ｳ (�)- ｳ
ｳ ﾁ ｳ ｳ
Current+ 1K ﾀﾂﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾂﾙ
Temp amp ｳ
ｳ>ﾄﾄﾄﾄﾁﾄﾄﾄR5ﾄ
IC1C
pin8
The -Ve going output of current Opamp IC1C that is also operated on over Volts
and Temperature, has just enough current to light the RED LED via the 1k & 470R
on doing so the GREEN LED goes out. The GREEN LED only lights if the +13.5V
output is good enough. All but the 1k are mounted to outside of the output
terminals with tight holes drilled for the LEDS, and +13.5 & 0V soldering to
the u1 cap leads that are across the terminals.
REPAIRING
Burnt out base emitter Rs means a 2N3055 is dud and has lost it's emitter
connection and it's driver will needed testing too.
This design is not that easy to work on you do need a flexible shaft 8mm
spinner!
ﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｿ
ﾜﾃﾄｿ fuse ｳ
Side View ﾟﾃﾄﾙ ｳ ﾞ p4 p2 p1 ﾞ ｳｳ
ｳ ｳｳmains ｳ ___ ｳ p3 o+ ｳｳ
ｳSWITCH ｳheat- Rect ｳｳlead ｳ -'' ''- ｳ th1 o ﾞﾝｳ
ﾜｳ ｳsinks ﾞﾝｳ ｳ / _ \ ｳ o o - ｳｳ
ﾟｳ----------- ｳ ｱCsｱ ｳｳ ｳｳ / \ ｳｳ o o ｳｳ
ﾜｳ MAINS |ｳ PCB ｱ ｱ ｳｳ ｳｳ \_/ ｳｳ - o o ﾞﾝｳ
ﾟｳTRANSFORMER|ｳ===============ｳｳ ｳ \ / ｳ ﾞ ++ o ﾞ ｳｳ
ﾀﾂﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾂﾄﾄﾄﾄﾄﾄﾂﾄﾂﾂﾄﾂﾙ ｳ -..___..- ｳ
ﾀﾄﾙ ~ ~ ﾀﾄﾙ ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾙ
Feet Transistors Feet Plan View
The 4 pass transistors are bolted on the underside with 2 sets of nuts, one to
hold transistors and internal heatsink to the case (no insulation kit needed in
this design!), and the 2nd set with washers holds the PCB in place. But the PCB
can only be removed after the 2 rectifiers have been moved out of the way.
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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