Aleph 30 power supply

jmmartins · 28th September 2007, 11:09 AM

I built an Aleph 30 and it works ok. The power supply as a 300 watt torroid 2x18v (ac). I should have about 25V after the rectifier bridge, however, when measured with the multimeter I get 17 v (ac) and only 20,5 V (DC). The current is 5Amp and have 6 capacitors of 15000 uF

Is it normal to get nearly 3,5 volts across the rectifiers (datasheet says 1,2V)? What could be wrong?

traw · 28th September 2007, 02:41 PM

Putting a beating on the transformer 5 amps of 8 (300va /36) so will sag 10-15%. I bet that transformer will get mighty warm.

Any losses across CRC?

I used 500va, 20x2 on aleph30.

Rule of thumb is 1.2 rather than 1.41 in these heavy current loads.

jmmartins · 28th September 2007, 04:47 PM

Traw
Thanks for your reply
You must be right, i have to change the torroid. It gets fairly warm, nothing to worry about but +- rails are on the short side, only +-21V
Across CRC, only 0,5V ... i use a 0,1 ohm resistor.

Well, another transformer for a chipamp i’m working on

28th September 2007, 11:09 AM	#1
jmmartins diyAudio Member Join Date: May 2005	Aleph 30 power supply I built an Aleph 30 and it works ok. The power supply as a 300 watt torroid 2x18v (ac). I should have about 25V after the rectifier bridge, however, when measured with the multimeter I get 17 v (ac) and only 20,5 V (DC). The current is 5Amp and have 6 capacitors of 15000 uF Is it normal to get nearly 3,5 volts across the rectifiers (datasheet says 1,2V)? What could be wrong?

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28th September 2007, 02:41 PM	#2
traw diyAudio Member Join Date: Sep 2005	Putting a beating on the transformer 5 amps of 8 (300va /36) so will sag 10-15%. I bet that transformer will get mighty warm. Any losses across CRC? I used 500va, 20x2 on aleph30. Rule of thumb is 1.2 rather than 1.41 in these heavy current loads.

28th September 2007, 04:47 PM	#3
jmmartins diyAudio Member Join Date: May 2005	Traw Thanks for your reply You must be right, i have to change the torroid. It gets fairly warm, nothing to worry about but +- rails are on the short side, only +-21V Across CRC, only 0,5V ... i use a 0,1 ohm resistor. Well, another transformer for a chipamp i’m working on

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