Lm329 pin2 is 6,83V, pin 2 and 3 are 6,82V both, OP1 is connected to +Vsense with a piece of wire.
now all seem to be working , what surprise me is that I need a 30Vac secondary transformer to get 24Vdc output without using the pre-reg.
If you have the opportunity to check with an oscilloscope you can see the min voltage of the raw voltage. It seems to be a bit much but this depends about the smoothing. Have you checked your ripple voltage?
You shouldn't, but it depends on how much reservoir capacitance you have and the load current.
30V AC would give around 40+V at the input to the regulator, 30V is all you actually need (maybe a bit less, depending on load and choice of pre-reg) BUT if the ripple on the raw supply is too high, it could cause the regulator to dropout.
What's the ripple on the raw supply, under load? You talked earlier about 1000uF, which is a tiny reservoir.
Andy.
Probably I missed something because I didn't expect I had to use smooth capacitors before the regulator, Alw manual didn't talk about it. Actually I have 1000mf in parallel with C1. Should I use some more complex crc filter ?
Giorgio
Giorgio
The manual only talks about the regulator and doesn't offer advice about building a basic DC supply to feed them.
I suggest a search around the net on DC PSU design might elicit some good background, unless anyone else can offer some good links.
In short though you need more than 1000u, for most supplies if you want to avoid ripple that can cause dropout.
What was happening on your supply is the voltage at the input was dropping below the minimum the regualtor needs, due to the high ripple voltage from the low capacitance you have.
PSU designer from Duncan's Amp Pages might help too.
http://www.duncanamps.com/software.html
Andy.
Are you using the tracking pre-reg?
If so, you need a bigger cap *before* the regulator input, *not* at the C1 location.
If you're not using the TPR, the C1 is as good a place as any to fit a cap (if practical), but >1000u is required.
Normally you'd design an off-board DC supply, with smoothing caps suitable to reduce ripple to acceptable levels given your load, then just connect the regulator to that supply.
Conceptually using the SR is the same as using a 3-terminal regulator, and the same requirements apply there too.
Andy.
Thanks Per and Alw, my problem was insufficient smoothing capacitors before the super-reg, now I applied 4400mf+0,47R+4400mf and now is all working the pre-reg and the reg. With 24Vac I have now a clean 24Vdc at the load. The problem was all here.
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