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12.6V from ATX instead of 12V?  Any ideas?
12.6V from ATX instead of 12V?  Any ideas?
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Old 29th October 2017, 05:08 PM   #11
wwenze is offline wwenze  Singapore
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The feedback can be tinkered on the secondary side... and then you can close the chassis back up.

There is no way for the secondary side to see 300+V unless you seriously screw it up and somehow connect the primary to the secondary. Which if you choose to use as your argument, is a fair one. But at this point of reasoning, all power supplies discussions including those using a 50Hz transformer should be taboo due to gross incompetence of the builder.

P.S. group-regulated PSUs still exist today. Not that I think cross-loading is a good way to increase the +12V.

Last edited by wwenze; 29th October 2017 at 05:15 PM.
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Old 29th October 2017, 05:49 PM   #12
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by kodabmx View Post
It's powering a TUBE AMP! The B+ is 380V. Not worried about it at all.
Well, you *should*
Voltage is never absolute but relative to another point.

* If you touch (accidentally or on purpose) the "+380V" node with a fingertip (or elbow or wrist or any other body part) but nothing else in that supply, specially its chassis or supply ground, nothing happens.

* if you touch *any* point in the *hot/live* side of that supply, you die , for the very good reason that already, always, you are touching "another point" : ground/earth/the floor.

You think both situations are the same?

Quote:
The feedback can be tinkered on the secondary side... and then you can close the chassis back up.

There is no way for the secondary side to see 300+V unless you seriously screw it up and somehow connect the primary to the secondary. Which if you choose to use as your argument, is a fair one.
If you are "tinkering" with the secondary side, you are handling/touching/holding one way or another a single board, palm sized, where you will be soldering/desoldering/modding on the admittelly safe secondary, 1 inch away from half the board which is live/hot.

The potential for error is there.

No need to connect secondary to primary, fully exposed hot parts are there at your fingertips.

Quote:
But at this point of reasoning, all power supplies discussions including those using a 50Hz transformer should be taboo due to gross incompetence of the builder.
You are comparing apples to oranges.

Standard power supplies are:

1) very simple, you only have to pay attention to power switch contacts, fuse ones, and little else, and they are "all together" on a separate, easy to avoid place, wires carrying mains voltage into the transformer are insulated, while *all* components and tracks on an SMPS primary side are hot and exposed.

2) when building an amplifier, mains wiring is made with everything unplugged and never touched again, while when tinkering with the board as needed here, you are handling and touching it and to adjust it must be on.

Again:
You think both situations are the same?
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Old 29th October 2017, 06:16 PM   #13
wwenze is offline wwenze  Singapore
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Quote:
you are handling and touching it and to adjust it must be on.
Nobody mentioned that.
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Old 29th October 2017, 06:41 PM   #14
leadbelly is offline leadbelly  Canada
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Quote:
Originally Posted by wwenze View Post
Nobody mentioned that.
Exactly. Thanks for that great example of the straw man logical fallacy JMFahey.
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Old 29th October 2017, 07:31 PM   #15
Chris888 is offline Chris888  United Kingdom
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Take care with the hot side of a switching PSU.
There can be a lot of energy stored in the caps. The residual current breaker on your bench isn't going to stop that hurting.

If the OP wants more than his PC supply will give, step up switchers are available on ebay for the price of a beer. But I'm sure many attics still contain PC supplies where loading the 5V will boost the 12V a little. Or you can buy a 15V smps for the price of two beers.
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Old 29th October 2017, 07:43 PM   #16
infinia is offline infinia  United States
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I hate to see the final product incorporating hacked DC/DC boost boards and a lone ATX supply. Time to re-think the whole purpose of audio tube / glowing glass circuits. IMO half the sound is all the big iron and copper. Besides the sounds, the sight of a HV Rectifier tube is pretty awesome..
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Old 29th October 2017, 10:05 PM   #17
TonyTecson is offline TonyTecson  Philippines
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12.6V from ATX instead of 12V?  Any ideas?
i worked om ATX psu's from 2000 to 2004 before i got deployed to Russia as an overseas worker.....seen a lot of those during those times...

if you want to work on them, an isolation transformer is a life saver...
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Old 30th October 2017, 05:26 AM   #18
TonyTecson is offline TonyTecson  Philippines
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12.6V from ATX instead of 12V?  Any ideas?
Quote:
Originally Posted by wwenze View Post
The feedback can be tinkered on the secondary side... and then you can close the chassis back up.

There is no way for the secondary side to see 300+V unless you seriously screw it up and somehow connect the primary to the secondary. Which if you choose to use as your argument, is a fair one. But at this point of reasoning, all power supplies discussions including those using a 50Hz transformer should be taboo due to gross incompetence of the builder.

P.S. group-regulated PSUs still exist today. Not that I think cross-loading is a good way to increase the +12V.
the feedback the controller is on the secondary side....
but the primary side of the chopper traffo feeds off the mains rectified
psu rectifier and caps and has no isolation from the mains...
and herein lies the issue....fraught with danger....

the new forum rules did not make the danger go away....it still is a safety concern...
the difference is, now we can talk about it...
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Old 30th October 2017, 08:20 AM   #19
TonyTecson is offline TonyTecson  Philippines
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12.6V from ATX instead of 12V?  Any ideas?
12 volt initiative by Intel.......https://www.intel.com/content/dam/ww...sign-guide.pdf

old Intel ATX psu design guide.....https://paginas.fe.up.pt/~asousa/pc-...pow_supply.pdf
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Old 30th October 2017, 01:28 PM   #20
Xoc1 is offline Xoc1  United Kingdom
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Switch Mode Supplies are everywhere.
There are many threads on modifying the Behringer DCX2496 crossover but not much mention of the Switch Mode power supply - It has exposed rectified mains voltages on the capacitor top - (A bit of tape helps here.)
Working on any device with high voltages is dangerous.
With the right information I don't see why the insides of an ATX PSU are different from almost any other consumer product.
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