Hi there, hoping someone could help me solve a few problems I'm having with a power supply I've built.
Basically its a dual rail power supply with a virtual ground, +12 -12 outputs. Got the design from a book, starting electronics construction by Keith brindley. Having built the circuit the -12v terminal is outputting 29v, and the + terminal is outputting 12v. The transformer is rated at 10va, and is series linked giving out 40v not underload. The regulators used are 7812 and 7912, why is it that the negative voltage is so high? Looks like voltage regulator isn't doing its job but I've replaced and still no change.
There are four capacitors two rated at 2200mf 25v, they poped so replaced with 50v 2200mf which has now made the +12 volt unstable.
The other smaller caps rated at 22 mf 16v have not poped.
Have tried supply underload and the neg voltage will drop down, but still not good for op amp circuits as they have a Max voltage 15v.
Please could someone try and explain what's gone wrong, I followed the book and checked the circuit over many times. I thought maybe transformer was outputting to high when not under load, but surley the 7912 should still be able to maintain a steady neg voltage.
Appreciate any replys if you can make sense of this, thanks.
Basically its a dual rail power supply with a virtual ground, +12 -12 outputs. Got the design from a book, starting electronics construction by Keith brindley. Having built the circuit the -12v terminal is outputting 29v, and the + terminal is outputting 12v. The transformer is rated at 10va, and is series linked giving out 40v not underload. The regulators used are 7812 and 7912, why is it that the negative voltage is so high? Looks like voltage regulator isn't doing its job but I've replaced and still no change.
There are four capacitors two rated at 2200mf 25v, they poped so replaced with 50v 2200mf which has now made the +12 volt unstable.
The other smaller caps rated at 22 mf 16v have not poped.
Have tried supply underload and the neg voltage will drop down, but still not good for op amp circuits as they have a Max voltage 15v.
Please could someone try and explain what's gone wrong, I followed the book and checked the circuit over many times. I thought maybe transformer was outputting to high when not under load, but surley the 7912 should still be able to maintain a steady neg voltage.
Appreciate any replys if you can make sense of this, thanks.