Power Supply

[bigkim100]

Ok, so I need a brute force 12v 6 amp (at least power supply. I bought one for 10 Canadian Bucks at a Rummage Sale, and it outputs only 9vdc. It uses an oooold± Silicon transistor 2n6576 and a ooooold 723c control ic.
Is it worth getting this thing going with a new circuit, as it has a monstrous Transformer and bridge rectifier, that all seem to be putting out correct voltages. It includes a nice big heat sync and a really heavy duty case.....should I keep it , or trash it??
The schematic (sort of) is included

 

[bertus]

Hello,

Late Tony van Roon made a benchtop power supply using the LM723.
In the schematic yoy will see wich components vary the voltage.

Bertus

 

[crutschow]

Since the transformer apparently has 20Vac at the secondary, there should be more than enough rectified voltage to allow the 723 to provide 12Vdc at its output.

 

[Martaine2005]

it has a monstrous Transformer and bridge rectifier

It's well worth keeping as large transformers are worth their weight in gold these days.

Martin

 

[Harald Kapp]

This supply uses mostly robust components. A failure is unlikely with one exception:
The most common issue here would be a fail of the electrolytic capacitor C1. As this power supply is obviously old, this capacitor may (will) have lost most if not all of its capacity. Replace by a new 4700 µF (or higher) 40 V (or higher) type.
My glass ball shows me a > 90 % chance that the power supply will work after that replacement.

If not, the regulator may be limiting the voltage due to external issued.

• Check the contacts of the current limit select switch (1.5 A, 150 mA, 15 mA) for good contact, clean them with contact cleaner if necessary.
• Check resistors R5, R6 and R7 for correct value.
• Check potentiometer VR1 for good contact, clean if necessary.
• If you have an oscilloscope, check the output voltage for cleanness. Is it clean or is there a noticeable ripple on top?

Regards,
Harald Kapp

 

[bigkim100]

I was lucky enough to find a basic schematic using the ic and transistor. With the schematic, I was able to remove all the assorted jigged up wires, that I think someone had used to bypass the ic. Many wires later, and a pile of wires removed I found that it worked perfectly. I have added a fuse, front panel Power On light, and used solid wire (since its supposed to put out 6 amps). I also replaced the 2 conductor wire with 3 conductor, so the metal case is grounded. So I now have a nice solid 12 v supply. I think what confused the original owner was that both the input and output negatives of the unit were common, and once I corrected the fact that he had disconnected this, it sprang to life. Thank you everyone for all your help, I do appreciate it. PS I also mounted the PC board that was just flopping around the inside of the case...Jeeeze...what were they thinkin!

 

[Martaine2005]

Do you mean primary and secondary?
Somebody will correct me, but wont that circumvent any isolation from the transformer?

Martin

 

[bigkim100]

Im sorry, I meant the low voltage dc side, pre and post regulation. Thank you tho