Hi all,
The assembly is the following: mains transformer 220 / 2x24Vac - stabilizer - the load that is powered at 2x15Vdc with a maximum consumption of 100-150mA.
The phenomenon is:
1 - when the assembly is powered by the network, all this work does not work, the voltage on the positive branch + 15Vdc and 0Vdc decreases somewhere up to 5Vdc and the value between 0Vdc and -15Vdc remains ok in the parameters.
2 - if I interrupt the power supply between the stabilizer and the load for an interval of 1-2 seconds everything works properly.
What is this phenomenon called, what is its cause and what is the remedy?
The assembly is the following: mains transformer 220 / 2x24Vac - stabilizer - the load that is powered at 2x15Vdc with a maximum consumption of 100-150mA.
The phenomenon is:
1 - when the assembly is powered by the network, all this work does not work, the voltage on the positive branch + 15Vdc and 0Vdc decreases somewhere up to 5Vdc and the value between 0Vdc and -15Vdc remains ok in the parameters.
2 - if I interrupt the power supply between the stabilizer and the load for an interval of 1-2 seconds everything works properly.
What is this phenomenon called, what is its cause and what is the remedy?
Please confirm you talk about the schematic in post 269
https://www.diyaudio.com/forums/power-supplies/164365-class-preamp-psu-27.html#post6169207.
Do I understand you correctly that the negative output is
fine and the positive drops with load ? In # 279 you wrote
it can be adjusted properly.
Check input voltages at rectifier under load also.
https://www.diyaudio.com/forums/power-supplies/164365-class-preamp-psu-27.html#post6169207.
Do I understand you correctly that the negative output is
fine and the positive drops with load ? In # 279 you wrote
it can be adjusted properly.
Check input voltages at rectifier under load also.
I put R of 3K9 same result
I put R of 3k6 the problem moved on the negative branch only the output voltage is -0.7v ...
Hi,
I managed to solve the problem with the help of a colleague.
After verifications we came to the conclusion that one of the branches did not synchronize perfectly with the other, that's why the BD140 transistor did not open and the source remained blocked on the '' + '' branch. A negative voltage of about ''-7Vdc'' appeared on this branch.
To prevent this from happening again, I added a 470nF capacitor between the collector and the emitter of transistors BC546 and BC556.
Now everything works perfectly.
Thanks for the help.
I managed to solve the problem with the help of a colleague.
After verifications we came to the conclusion that one of the branches did not synchronize perfectly with the other, that's why the BD140 transistor did not open and the source remained blocked on the '' + '' branch. A negative voltage of about ''-7Vdc'' appeared on this branch.
To prevent this from happening again, I added a 470nF capacitor between the collector and the emitter of transistors BC546 and BC556.
Now everything works perfectly.
Thanks for the help.
Attachments
Im confused. Pls forgive this noob. So all this is about a power supply for a pre-amp. X Voltage Y mili amps.
Why is it so complex ?. Whats wrong in using a LM78xx/79xx regulator or even a simple circuit with a zener diode of desired voltage and resistor. Or if you want a really clean signal. Why not two Li-Ion bats which power the circuit when on. And when off the bats are charged.
Sorry for this noob question.
Why is it so complex ?. Whats wrong in using a LM78xx/79xx regulator or even a simple circuit with a zener diode of desired voltage and resistor. Or if you want a really clean signal. Why not two Li-Ion bats which power the circuit when on. And when off the bats are charged.
Sorry for this noob question.
The LM78xx/79xx are also this complicated inside, they're just all wrapped up in a single component. A discrete design might have advantages in heat dissipation, or in being tailored to a particular circuit, or some other advantage over the very general-purpose LM78xx/79xx.
Some people do use batteries. I'm not sure Li-Ion would be a good choice as they usually have electronics on the output to prevent full discharge which might dirty up the supply. But I'm only speculating here; I don't know much about them.
Some people do use batteries. I'm not sure Li-Ion would be a good choice as they usually have electronics on the output to prevent full discharge which might dirty up the supply. But I'm only speculating here; I don't know much about them.