Does this transformer happen to have a multi-tap primary? I just pulled a stunt raising the voltage on the secondary by judiciously playing with the taps on the primary. Note that this is only good for about 10% or so at most, and that most transformers today have dual primaries, but not multi-tapped ones. Whether you'll be able to raise or lower the voltage on the secondary will depend on the line voltage in your area. Come to think of it, it's likely that you'll only be able to raise the voltage.
Geoff's solution is a good one if you don't mind doing surgery on the transformers.
Grey
Geoff's solution is a good one if you don't mind doing surgery on the transformers.
Grey
hum, i would rather not unwind the xformer. if its the last option, i can do it though.
here is my thought... i talked with some people at the electronics surplus shop i goto. they seem to think that taking two caps and wiring them in series will give you twice the voltage, and half the capacitance. so, a 1,000uf cap (50v) wired in series with the same cap will give you two 5,000uf 100v caps. is that right? someone on here said you woud need 4, they disagreed with that, and from what ive learned, i disagree too.
if that's the case, i could just go with double the caps in series, i would be fine with that.
i would rather keep the rails high, as i will have pretty good heatsinking, and the case will be nice and thick for sinking as well. i actually just got some renderings done and threw them up on my site. here is one:
http://www.cowanrg.mesanetworks.net/projects/images/aleph2/case3.jpg
this is just the basics, i dont have screw holes, etc... goto my site for more info if you wish. but the side plates that the heatsinks connect to are 1" thick, plus the huge heatsinks.
anyways, thats what im thinking. if i can do that, im willing to just buy double the caps. im (believe it or not) a good amount UNDER budget for this project, and i have little left to buy (just little odds and ends at this point).
thanks again guys.
here is my thought... i talked with some people at the electronics surplus shop i goto. they seem to think that taking two caps and wiring them in series will give you twice the voltage, and half the capacitance. so, a 1,000uf cap (50v) wired in series with the same cap will give you two 5,000uf 100v caps. is that right? someone on here said you woud need 4, they disagreed with that, and from what ive learned, i disagree too.
if that's the case, i could just go with double the caps in series, i would be fine with that.
i would rather keep the rails high, as i will have pretty good heatsinking, and the case will be nice and thick for sinking as well. i actually just got some renderings done and threw them up on my site. here is one:
http://www.cowanrg.mesanetworks.net/projects/images/aleph2/case3.jpg
this is just the basics, i dont have screw holes, etc... goto my site for more info if you wish. but the side plates that the heatsinks connect to are 1" thick, plus the huge heatsinks.
anyways, thats what im thinking. if i can do that, im willing to just buy double the caps. im (believe it or not) a good amount UNDER budget for this project, and i have little left to buy (just little odds and ends at this point).
thanks again guys.
Two 1000uF 50V caps in series equals one 500uF 100V cap so, yes, it will take four times as many caps to equal the original capacitance.
And as Geoff pointed out earlier, you should use resistors in parallel with the caps in order to ensure that the voltage stays put. Otherwise, the voltage midpoint between the caps will tend to drift, with potentially disasterous consequences. No need to lose a lot of current to these resistors--anywhere from 10k to 100k will do just fine. One resistor to each cap. Tube people do it all the time. In fact, I'm running 575V rails on two 350V caps in series (with, as I recall, 100k 2W resistors--you won't need 2W resistors, 1/2 to 1W will do, depending on what value you choose).
Grey
And as Geoff pointed out earlier, you should use resistors in parallel with the caps in order to ensure that the voltage stays put. Otherwise, the voltage midpoint between the caps will tend to drift, with potentially disasterous consequences. No need to lose a lot of current to these resistors--anywhere from 10k to 100k will do just fine. One resistor to each cap. Tube people do it all the time. In fact, I'm running 575V rails on two 350V caps in series (with, as I recall, 100k 2W resistors--you won't need 2W resistors, 1/2 to 1W will do, depending on what value you choose).
Grey
hum... 36 big can caps in one case. thats a whole lot. ill have to measure them and see if it can be done. i have a lot of extra room. most of the circuit boards will be embedded into the case, so the xformer and rectifiers will be inside the case in addition to the caps, and thats about it.
How about a "CQC"? Relatively small capacitor up front, with whatever voltage rating you need, then a capacitance multiplier (transistor) with a zener diode to drop the voltage, then a big capacitor at lower voltage on the output.
This is only practical if you don't need to drop that much voltage. You may want to consider getting or building a dummy load to do some experiments.
Stay away from those people in the capacitor store; that's pretty bad advice they're giving.
Or how about a light bulb in series with the primary?
This is only practical if you don't need to drop that much voltage. You may want to consider getting or building a dummy load to do some experiments.
Stay away from those people in the capacitor store; that's pretty bad advice they're giving.
Or how about a light bulb in series with the primary?
hum. you guys give me too much credit.
yeah, those guys were wierd... they kept suggesting a switching supply. he said he didnt know of any good amps that used linear supplies, they all used switching. i didnt even argue. i didnt even come in for advice, just for caps.
i think if i can fit enough caps in there, i will just go that route. at $2 each, its a good price. i just hope they have 72 of them
yeah, those guys were wierd... they kept suggesting a switching supply. he said he didnt know of any good amps that used linear supplies, they all used switching. i didnt even argue. i didnt even come in for advice, just for caps.
i think if i can fit enough caps in there, i will just go that route. at $2 each, its a good price. i just hope they have 72 of them
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