Hello everyone,
I am on the way building Aleph5, but I face the problem on the PSU DC voltage. I have arrange the PSU as the picture.
The transformer secondary voltage is 2X25VAC 750VA, and the actual value I measure was 27 VAC.
After power up, it work OK, but I only get 32V maximum DC output with no load. I think it suppose to be at least 34V? what is possible to go wrong? any idea?
Thank you
I am on the way building Aleph5, but I face the problem on the PSU DC voltage. I have arrange the PSU as the picture.
The transformer secondary voltage is 2X25VAC 750VA, and the actual value I measure was 27 VAC.
After power up, it work OK, but I only get 32V maximum DC output with no load. I think it suppose to be at least 34V? what is possible to go wrong? any idea?
Thank you
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I am not really sure, but I use 27VAC that I actually measured from the secondary side.
Mutiply by 1.414 will get 38VDC. I take out 1.5V for full wave rectifier then I should get more than 35VDC with out load?
I have noticed that a transformer may read a little high without any load so I might be tempted to at least put some small load on the secondary even a 25 to 100 watt light bulb. Another thing it's easy to overlook that you lose about 2v across the bridge rectifier so DC out is AC X 1.41 - voltage lost across the rectifier .
It's the opposite. Not enough capacitance will give lower voltage. Perhaps your capacitors are not functioning properly or their connections are not working properly.
I have loaded it with 2 channel of over bias aleph5. Total current draw was 6 A
The voltage before R was not change and same as the voltage measureed when no load, Just only the output dc voltage which droped by 1 V from CRC filter.
It seem to be work normally except the DC voltage after rectifier which was quite low.
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What AC voltage across the secondaries do you measure when the DC outputs are loaded?
If that is normal, maybe the wrong value of resistors for the CRC filters.
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Only if your mains voltage is sinusoidal. The 27VAC is an RMS measurement/approximation depending on how your multimeter works.
I have not measured the AC voltage because all connector was covered by heat shrink tube.
But I have measured the DC voltage before resistors and it was around 32VDC both load and no load. And voltage drop across the resisters was as I expected.
In my understanding, voltage was same for no load and load mean the transformer regulation is not bad. But I don't know why I get lower voltage after rectify.
Interesting point. Is that possible for too distorted wave form in the power line to effect quite a lot.
It's possible. If you measure 32Vdc then the peak AC is about 33.4V and the RMS of a perfect sinewave would be about 24V. You are measuring 27V or about 10% too high. It could be multimeter accuracy and/or a distorted mains waveform.
Large appliances can distort the mains and sometimes you can hear their effect when your transformer makes buzzing sounds.
Is this low voltage effect to the power amp, aleph 5 need dual 35 v supply? Should I measure the power line wave form?
Yes, I just only worry about the voltage. It seem to be too low for aleph5? At around 32v.
Thank you, I keep on going
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