there is a bottom and top? but it is ac, i thought it wouldnt make any difference. do you mean the secondary or primary windings?
On the schematic, D2 should connect to the transformer where D1 does, not on the other end of that winding. Otherwise, the voltage will not be doubled.
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i have it wired exactly like the diagram. maybe i need to sleep on it and take fresh look to-morrow
Are you measuring for DC across C3?
If it's wired correctly and you get about 160 to 180 V DC (or average) across C3 instead of about 330 V DC, then one of D1, D2, C1, or C2 might be shorted.
Actually, if D1 or D2 were shorted, you'd get about 174 volts average (177 V RMS) across C3, but with about 95 volts of 60 Hz AC riding on it.
If C1 or C2 were shorted, you'd get about 165 V DC across C3, with probably about 306 mV of 60 Hz ripple riding on it.
And if everything is OK, you should get a nominal 329 V DC across C3, with about 320 mV of 60 Hz ripple. (Values may be different, depending on load. I assumed you would be pulling about 70 mA from it.)
Cheers,
Tom
If it's wired correctly and you get about 160 to 180 V DC (or average) across C3 instead of about 330 V DC, then one of D1, D2, C1, or C2 might be shorted.
Actually, if D1 or D2 were shorted, you'd get about 174 volts average (177 V RMS) across C3, but with about 95 volts of 60 Hz AC riding on it.
If C1 or C2 were shorted, you'd get about 165 V DC across C3, with probably about 306 mV of 60 Hz ripple riding on it.
And if everything is OK, you should get a nominal 329 V DC across C3, with about 320 mV of 60 Hz ripple. (Values may be different, depending on load. I assumed you would be pulling about 70 mA from it.)
Cheers,
Tom
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im getting 60volts across the capacitors. i have been over it a few times and im not seeing the problem.
look a little closer againD1 and D2 should each have AC sitting between 0v and 337 V across them, with an RMS voltage of about 206V RMS across each one (and an average voltage of about 167 V across each one).
C1 and C2 should each have about 167 V RMS (and average) across them, i.e. basically 167 V DC with about 2.9 V P-P of spiky reverse-sawtooth ripple.
What does your meter read if you connect it between ground and the point where D1 abd D2 connect to the transformer winding?
C1 and C2 should each have about 167 V RMS (and average) across them, i.e. basically 167 V DC with about 2.9 V P-P of spiky reverse-sawtooth ripple.
What does your meter read if you connect it between ground and the point where D1 abd D2 connect to the transformer winding?
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i get 74v between that point and ground and the same across the individual caps. im supposed to get a total of 215 from both caps.
thanks
i measured it in dc though, i think. yeah i did. when i plug it in the measurement is about 130 across one then drops down to about 70
thanks for your help
OK. That's interesting. Maybe disconnect the load and try it. But I don't think that's it. The only thing I can think of is D1 or D2 being partially shorted, i.e. if one of them was acting like it had about 10 Ohms in parallel with it.
I would replace the diodes. While I was at it, I would make sure they're good for somewhere between 10 and 30 Amps each, since they each get a big current spike (depending on secondary's resistance, etc), for a couple of ms, every time it's turned on.
I would also make sure that C1 and C2 are low-ESR types, with large maximum current ratings, since they will see initially-large spikes of current, too, and might have to handle up to 1 or even 2 Amp current spikes continuously.
By the way, have you double-checked the polarities of the electrolytics?
Going back to the basics, for a minute, your 120 VAC RMS will have peak voltages of about +/- 170 Volts (i.e. 120 x 1.414, where 1.414 is sqrt(2)). So the rectified DC voltage will be only slightly less than that, due to the diode drops. So each cap (C1 and C2) should have a little less than 170 V DC across it. And the total across both of them should be double that, or about 332 volts.
I would replace the diodes. While I was at it, I would make sure they're good for somewhere between 10 and 30 Amps each, since they each get a big current spike (depending on secondary's resistance, etc), for a couple of ms, every time it's turned on.
I would also make sure that C1 and C2 are low-ESR types, with large maximum current ratings, since they will see initially-large spikes of current, too, and might have to handle up to 1 or even 2 Amp current spikes continuously.
By the way, have you double-checked the polarities of the electrolytics?
Going back to the basics, for a minute, your 120 VAC RMS will have peak voltages of about +/- 170 Volts (i.e. 120 x 1.414, where 1.414 is sqrt(2)). So the rectified DC voltage will be only slightly less than that, due to the diode drops. So each cap (C1 and C2) should have a little less than 170 V DC across it. And the total across both of them should be double that, or about 332 volts.
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im using a new protoboard. is it important to prep it with some denatured alcohol or something. i think i read something to that affect, could this be causing a slight short?
im using 1n4007s. i dont think they are rated for that high a current. oh, they can handle 30 amps Ifsm 30 amps for one cycle
allright. thanks a lot im signing off for the night time to listen to a symphony on the st70
i disconnected the output transformer and now i get good voltages across a cap - 146v. so i must have a bad connection somewhere after the whole voltage doubler circuit i guess
i get a 197.5 ohm resistance on the primary winding of the output transformer. i this normal? one wire is blue and one is brown, does it make any difference if i interchange this two?
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