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Old 9th January 2013, 03:39 AM   #1
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Default power supply problem

Hi And thanks for reading this post.

The ac output on my quad 405-2 amplifier's transformer is 71 volts but keeps going up and down by approximately 0.1- 0.3 volts everytime i measure it. Is this normal and is this the correct voltage. It is quite and old transformer from the 70's and i want to connect some new quad amp boards to it but am not sure if the output voltage is correct, or if anything can be gained by exchanging for a new toroid/audio transformer.

Many thanks in advance. John.
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Old 9th January 2013, 04:10 AM   #2
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Nothing wrong with the variations and r normal.

Gajanan Phadte
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Old 9th January 2013, 07:35 AM   #3
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Default Power supply

Hi. The variations are ok, but what do you think of the output voltage.

Thank you.John.
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Old 9th January 2013, 08:03 AM   #4
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by goodsguys View Post
Hi. The variations are ok, but what do you think of the output voltage.

Thank you.John.
Sounds OK to me. The Quad ran on a pseudo -/+50 volt supply. So 100 volts divided by root 2 gives 70.7 volts AC. Spot on.
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Old 9th January 2013, 09:42 AM   #5
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Hi,

If power supply is not suffient or other problems take a look at

Antek - Your reliable source of transformers, power supplies, and more.

i bought all different types over there: example As4224 (400 watt, 24 volt).
It produces 24 ampere if needed. super silent and purple ground wire really makes it "silent".
It took my L20 amps (350 watt ,4 ohm)to a new level.

also the lead wires and insultation are the best i have seen on many different type of toroidals.
i use them on 230 volt (they are suited for 115 volts and 230 volts).

Also for a DAC i use from them a separate 9 volt (an209)and a 12 volt (an0212)toroidal. great sound.
i used before a combi toroidal 9volt+12 volt.


The sound improvement is dramatic/to a higher next level .

For speaker protect kit : i use in the power amp a AS0512 which is 50 VA.
It sounds high but i works faster and more stable than a 25 VA model.
And this one has a purple ground wire to make pre-amp perfect.

Best regards,

Marco
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Old 10th January 2013, 02:47 AM   #6
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Thanks so much for the reply.

For the smoothing capacitors I am thinking of replacing with panasonic fc caps 1000uf x 10. I have tried the panasonic fm's before in a dac and loved the results but unfortunately they are only available up to 50 volts so may give the fc's a try.

Do you think this is a good idea or should i use one large capacitor. I am a little worried about so many soldering joints but it may pay off with lower esr.


Many thanks in advance. John.
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Old 10th January 2013, 06:01 AM   #7
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Location: Los Angeles
Quote:
Originally Posted by goodsguys View Post
Hi And thanks for reading this post.

The ac output on my quad 405-2 amplifier's transformer is 71 volts but keeps going up and down by approximately 0.1- 0.3 volts everytime i measure it. Is this normal and is this the correct voltage. It is quite and old transformer from the 70's and i want to connect some new quad amp boards to it but am not sure if the output voltage is correct, or if anything can be gained by exchanging for a new toroid/audio transformer.

Many thanks in advance. John.
Since you posted exactly the same thing on HydrogenAudio, here is the same answer.


Do you think the line Voltage is a constant? It wobbles all over the place. If you try your test with a brand new first time plugged in unit you'll find the same thing. If the line Voltage WAS constant, why would we need regulators? - And nearly every solid state gadget you own has regulators - LOTS of them. Power supply regulators are an art and science of their own.

G
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Old 10th January 2013, 06:36 AM   #8
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Hi. Sorry, I didn't know that. I'm not an electrician just a hobbyist.

I have posted the same question elsewhere because sometimes i do not get a reply and also i like to get a few different points of view I hope you do not take it offensively as this is not my intent.

Many thanks for the info.
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Old 10th January 2013, 09:25 AM   #9
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Location: Los Angeles
Quote:
Originally Posted by goodsguys View Post
Hi. Sorry, I didn't know that. I'm not an electrician just a hobbyist.

I have posted the same question elsewhere because sometimes i do not get a reply and also i like to get a few different points of view I hope you do not take it offensively as this is not my intent.

Many thanks for the info.
You'll find both forums to be pretty helpful. Your Voltage shifting is lower than at my house. On hot days with lots of A/C running our line has dropped as low as 99 Volts and as high 125. Some of the old gear gets downright cranky on low Voltage in particular the Technics SH-9010 equalizer. Switching supplies in the PCs and monitors I've seen run as low as 67 when one of the 3 phases failed nearby. BTW it's a good idea to NOT run on the lower Voltages.

I saw the post on Hydrogen and replied and then saw what looked to be an identical post here - it is.

Bottom line - your stuff is fine - at least the transformers.

G
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Old 10th January 2013, 09:34 AM   #10
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Im sure this is in the wrong section .... "Chipamps"??
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