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Old 24th August 2005, 12:47 PM   #1
Phill is offline Phill  France
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Default high voltage on aleph 5

hello

my power supply for a aleph 5 : CRCRC

for a mono block
2 x 30 V, 500 VA
2 bridges
R = 0.5 ohm
6 x 68000F/50v

the nominal voltage is 34V
I obtain a tension of 42.5V, as in the books! (the amplifier board is not connected )
I connect or not
I don't like smoke
the tension should fall... but is this sufficient?


many aleph 5 were built with transformers of 2 X 30 v
how do they make?
thank you
Phill

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http://domainedupossible.free.fr/pag...H5/aleph51.htm
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Old 24th August 2005, 01:57 PM   #2
rchua77 is offline rchua77  Singapore
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Since your transformer is 500VA, it can supply up to 8.3A.

With 42V on the supply rail and 4A biasing, you could have up to 95W into 8ohms and 128W into 4ohms with 50% current gain.

With the Aleph5 you built using 6 output devices, each output device is dissipating 56W. Not good, you need at least 12 output devices to bring the power dissipation down to under 30W.

Just make sure you have sufficient output devices with enough heatsinking to keep the junction temperature of the devices low and the heatsink temperature less than 70C.

Alternatively, you should reduce the voltage rails to make a lower power version.

Nothing should smoke if you wired up the board and outputs correctly.
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Old 24th August 2005, 02:45 PM   #3
Phill is offline Phill  France
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hello

I can regulate the bias with R19, 2 A ==> 76W/9.5ohm end 28W dissipation/fet...or less if necessary


for the moment, I risk only one problem of dissipation...? it is that?

end the 3 capacitors 220F/35v????


Thanks
Phill
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Old 24th August 2005, 03:35 PM   #4
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With 4A bias and the 0.5 Ohm resistors in the CRCRC you should also loose another 4V per rail when connected.
You should not worry about the 220/35 C's, these will never see this voltage.

Please correct me if mistaken.
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Old 24th August 2005, 05:33 PM   #5
SvErD is offline SvErD  Norway
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Default Re: high voltage on aleph 5

[QUOTE]Originally posted by Phill
[B]hello

my power supply for a aleph 5 : CRCRC

for a mono block
2 x 30 V, 500 VA
2 bridges
R = 0.5 ohm
6 x 68000F/50v

the nominal voltage is 34V
I obtain a tension of 42.5V, as in the books! (the amplifier board is not connected )
I connect or not
I don't like smoke
the tension should fall... but is this sufficient?


many aleph 5 were built with transformers of 2 X 30 v
how do they make?
thank you
Phill



According to PSUD you should be just fine.
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Old 24th August 2005, 06:46 PM   #6
Phill is offline Phill  France
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that is reassuring!

thanks
Phill
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Old 26th August 2005, 12:36 PM   #7
Phill is offline Phill  France
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hello

I connected a board amplifier
tension aux rails : +/- 38.8 v
tension Z5 : 9.08V
R11 : 5.36 v
R14 : 4.42 v
VgsQ1 : 3.64v
VgsQ2 : 3.64v
VgsQ4 : 3.74 v
resistances fet + : 626,652,610mv
resistances fet - : 634,632,625mv
Is the matching good ???
offset 11mv

that heats!

the second board does not function!
I must find the breakdown

Phill

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Old 26th August 2005, 10:33 PM   #8
Jaac is offline Jaac  Netherlands
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hello there i have also 2 torroids of 2 X 30 Volt but i'am still working on the case

Click the image to open in full size.

for more pic's photo album

for now i will first use 2 x 47.000 uF 50V elco's maybe later i will put some nice CLC or CRC filter in it. But for all i know is that i can use 6 diveces (FET's) per channel i still did not build them in my case. is it better to put some extra ?? and must i make some changes to the origenal aleph 5 design ??

gr Jaac
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Old 26th August 2005, 10:49 PM   #9
Magura is offline Magura  Denmark
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Jaac, a word of advice.

Do not use the mounting bolt of the trafo to mount anything else but the trafo. I fail to remember whom did that a while ago, but he had a lot of problems from it. He grounded the sheilding plate as well, in itself not a bad idea, but when mounted on top of the trafo you get a shorted turn on the trafo.....and lots of heat (and with patience some smoke and a bit of fireworks as well).

Magura
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Old 26th August 2005, 10:57 PM   #10
Jaac is offline Jaac  Netherlands
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Quote:
Originally posted by Magura
Jaac, a word of advice.

Do not use the mounting bolt of the trafo to mount anything else but the trafo. I fail to remember whom did that a while ago, but he had a lot of problems from it. He grounded the sheilding plate as well, in itself not a bad idea, but when mounted on top of the trafo you get a shorted turn on the trafo.....and lots of heat (and with patience some smoke and a bit of fireworks as well).

Magura
but the bolt i use is made from stainles steel does that make any diverence ?? i hope so. at mi work we have a philips stabilisor it have some big trafo's in it the case its in is 3/4 steel and 1/4 ( the back panel) made of stainless steel to undone that shorted turn of the trafo. so i tought a stainless steel bolt will prefent that i hope.
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