What gives here?
All measurement seem correct until I rectify. 35v secondaries showing what I might assume....but the DC is coming out way low....like 20volts low. Should be 51 or so (this is for a tpa3255).
I thought maybe it is an RMS thing with my DMM but even so the numbers dont add up.
Measured the BR in diode mode and got 0.9 between both 'sides'...whatever this tells us....assuming the voltage drop of 2 diodes so I will have lost 1.8v through the BR.?
But where did the other 18v go?
All measurement seem correct until I rectify. 35v secondaries showing what I might assume....but the DC is coming out way low....like 20volts low. Should be 51 or so (this is for a tpa3255).
I thought maybe it is an RMS thing with my DMM but even so the numbers dont add up.
Measured the BR in diode mode and got 0.9 between both 'sides'...whatever this tells us....assuming the voltage drop of 2 diodes so I will have lost 1.8v through the BR.?
But where did the other 18v go?
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You've got no capacitance across the bridge - so the meter will read an average/ rms of the rectified sine, less the two diode drops. (0.7 x 35)-1.5v, say - pretty much what you DMM shows.
Add even just 100uF and try again 🙂
Add even just 100uF and try again 🙂
Back home with access to the cap bank that I have made for this project....better result!
Came out lower than calculated which I am pleased about actually as if it was 52v then it may have started to over volt the amp.
Are bleeder resistors the done thing.?...this thing is holding charge for ages.
Came out lower than calculated which I am pleased about actually as if it was 52v then it may have started to over volt the amp.
Are bleeder resistors the done thing.?...this thing is holding charge for ages.
For a power amp, yes, not a bad idea.
10K ohm should work well enough; that's about 5mA draw per rail, so not a gross waste of power in use, and dissipate about (50 x 50) / 10000 = 0.25w in use; I'd suggest using resistors rated for 1w or more.
And questions like this are not a waste of anyone's time - might help someone else another time. That's why people posting follow-ups on how problems were resolved is always appreciated 🙂
10K ohm should work well enough; that's about 5mA draw per rail, so not a gross waste of power in use, and dissipate about (50 x 50) / 10000 = 0.25w in use; I'd suggest using resistors rated for 1w or more.
And questions like this are not a waste of anyone's time - might help someone else another time. That's why people posting follow-ups on how problems were resolved is always appreciated 🙂
