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10 Amps power supply with LM723

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xavier60:

--- Quote from: mike_mike on September 22, 2019, 11:41:55 am ---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.

--- End quote ---
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:

--- Quote from: xavier60 on September 22, 2019, 12:16:40 pm ---Even BC557 would do if the unreg rail isn't much higher than 30V.

--- End quote ---

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:

--- Quote from: mike_mike on September 22, 2019, 12:37:27 pm ---
--- Quote from: xavier60 on September 22, 2019, 12:16:40 pm ---Even BC557 would do if the unreg rail isn't much higher than 30V.

--- End quote ---

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 ?

--- End quote ---
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:

--- Quote from: mike_mike on September 22, 2019, 02:41:20 pm ---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.

--- End quote ---
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.

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