10 Amps power supply with LM723

[xavier60]

Hello,
I have found the attached power supply schematic.
Can you please help me with part numbers for replacement transistors TR3-TR6 (A823) and TR2 (3223) ?
The replacement transistors are not really necessary to be pin to pin compatible, because I can redesign the pcb layout.
I would also like to know the voltage for ZD3, the part number for D4 (1N4148 ?) and the secondary voltage of the transformer.

BC556 will be Ok for TR3-TR6. Even BC557 would do if the unreg rail isn't much higher than 30V. T3 sees very little voltage.
D45H11 for T2.

Quoted from ON Semiconductor,
"
These series of plastic, NPN and PNP power transistors can be used as general purpose power amplification and switching such as output or driver stages in applications such as switching regulators, converters and power amplifiers."
https://www.onsemi.com/products/discretes-drivers/general-purpose-and-low-vcesat-transistors/d45h11

[mike_mike]

Even BC557 would do if the unreg rail isn't much higher than 30V.

I need output voltage up to 50V (as it is written on the schematic). In this case, the unreg rail will be more than 30V. This means that I will need to use transistors with higher collector to emitter voltage...
For example, 2N5401 is a good replacement for TR3-TR6 ?

[xavier60]

Even BC557 would do if the unreg rail isn't much higher than 30V.

I need output voltage up to 50V (as it is written on the schematic). In this case, the unreg rail will be more than 30V. This means that I will need to use transistors with higher collector to emitter voltage...
For example, 2N5401 is a good replacement for TR3-TR6 ?

That should be fine.

[mike_mike]

What replacements (equivalents) do you recommend for BF422 and BF423 from the attached schematic ?
Can BF422 be substitute by 2N5551 and BF423 by 2N5401 ?
They do not need to be pin to pin compatible, I can redesign the pcb layout.

[xavier60]

What replacements (equivalents) do you recommend for BF422 and BF423 from the attached schematic ?
Can BF422 be substitute by 2N5551 and BF423 by 2N5401 ?
They do not need to be pin to pin compatible, I can redesign the pcb layout.

The current ratings of the 2N5551 and 2N5401 are unnecessarily high but should not cause a problem.
That circuit has delayed over current shutdown but no fast limiting.
Which can be fixed by putting C3 across BE of TR2.

More: I'd be curious to know what the current gain measures when you receive the 2N5551 and 2N5401 transistors.

[LaserTazerPhaser]

The ARRL (American Radio Relay League) has some 30V/10A supply suggestions.

Important things are:
- adequate cooling (fan)
- bridge rectifier with sufficient current loading capability (20A min)
- 4 x 2N3055
- frequency compensation (see ARRL schematics)
- overtemp protection
- output crowbar to protect your load if something goes wrong.

http://www.dd1us.de/Downloads/an%20rf%20proof%2030%20amps%20power%20supply%201_0.pdf

Power supply doesen't need stud diode heatsinks, D1 & D2 studs can be replaced with a few ganged high efficiency schottkies dpak or other smt parts.

Aren't electrolytics inappropriate for mains side applications?

[ArthurDent]

LaserTazerPhaser - "Aren't electrolytics inappropriate for mains side applications?"

The capacitors you marked are not polarized. The curved electrode generally indicates outside foil. There is no + or - that you would see on electrolytics. Check the values and you'll see they can't be electrolytics.

[mike_mike]

More: I'd be curious to know what the current gain measures when you receive the 2N5551 and 2N5401 transistors.

hFE for 2N5401 is 180 and for 2N5551 is 163.