Since I have very nice screened, potted and sealed Avel Lindberg toroidal transformers with 50VA and 2x15V: Can I use them for the Folded or will the voltage be too low?
Normally it will be too low. But some transformers overshoot spec while mains overshoot too in some places. So do a test seeking 43VDC as minimum after rectification and filtering when the bleeder resistors are installed as load too.
Going well. You don't need the Silpads for the Mosfets unless you know there will be possibility for the sinks shorting to ground accidentally.
Thank you, Salas.
Right now I have 44.3V with a 6k8 bleeder resistor, which I had at hand. Very tight, I would say, but ...
I will measure all 4 transformer I have.
Right now I have 44.3V with a 6k8 bleeder resistor, which I had at hand. Very tight, I would say, but ...
I will measure all 4 transformer I have.
...well, that was a typo - wishful thinking, maybe.
All 4 transformers vary between 43.1V and 43.4V with 4700uF/6k8, with a momentary mains voltage of 229V.
That is pretty low, but maybe manageable. What do you think?
All 4 transformers vary between 43.1V and 43.4V with 4700uF/6k8, with a momentary mains voltage of 229V.
That is pretty low, but maybe manageable. What do you think?
They will be lightly loaded in this case. They did not show appreciable difference from bleeder test to full test in my proto (R-Core).
Not bad if this mains is your low side average. I get 233V on average here for instance and 229-231V when seldomly low.
Yes, I know, but put them for testing and until I receive the recommended sinks.
Just watch the temperature on the Q6x sinks, they look thin to me. It won't die though.
@ lohk
Keep in mind one rule. I don't want you to have Raw DC to Rail on PCB difference less than 6V worse case. If you will meet that rule, your transformers are keepers.
Keep in mind one rule. I don't want you to have Raw DC to Rail on PCB difference less than 6V worse case. If you will meet that rule, your transformers are keepers.
It seems to that this is also low here - it can get over 235V at times. So it is tight, but ok. Great!
The bleeder resistor, although higher specified, gets very warm, almost too hot to touch. Why do we need that resistor? It may has been discussed before, but I have missed the deeper meaning of an heavy load before the actual power supply, which is a heavy load itself. Does it make the psu less noisy?
That is why I specified 2x2W 10k in parallel. To share heat. Mount them with some little distance from the board also, if you are using a perf board at all. It both makes it bit less noisy over the umbilical cable and drains it out in acceptable time both for operation LEDS to extinguish and not to hold charge for when unplugging.
Just built one of my power supplies and getting 59vdc after rectifiers, smoothing and with load resistors. Trafo is 230vac, 0-18 0-18vac 30va. I am measuring my mains at 233vac and the output from the trafo is 42vac. I think I need some series resistors to reduce the output voltage to more acceptable levels, any suggestions?
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The transformer is too happy for its stated spec. Another user showed 48DCV for same labeled Tx couple of days ago. Use Duncan PSU free simulator for 100mA load per channel and try resistor values between the bridge and the filter capacitor until you will lose 10-12V. Use 3-5W for real resistors and whatever value you will end up with in the simulator.
36Vac on load changing to 42Vac off load, indicates a transformer regulation of 16.6%.
That is normal for a 30VA toroid. A 30VA EI would have an even higher regulation.
Very small transformers can even exceed 30% regulation.
It takes little current draw (load) to reduce the smoothed DC voltage.
Hi Salas, sorry if this question is being asked before. The 117gr stated in the build guide are 3-4mA ( regulator section) and 4-5mA in the phono part. I measured about 20 of my stash and got only one 3.68mA, the rest are from 4.5 up to 5.6mA. Which ones should i use?.
Quan
Quan