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Old 7th February 2008, 10:52 AM   #41
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Ok i have built my psu. Its a 500 va 0-25 x2 unit running into a seperate bridge rectifier per channel. the + on one tied to the negative of the other.I have 22,000 uf between each rail and 0v. My issue is that i get about 26 v rail to neg without caps and 36v (what i was expecting) with caps. Is this right, i am guessing it is cos obviously i should get 25v x 1.41.

Almost ready to fire em up!!
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Old 7th February 2008, 09:52 PM   #42
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Current stage, progressed slowed a great deal my deadly man flu
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Old 8th February 2008, 09:58 AM   #43
Dave S is offline Dave S  United Kingdom
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NAP140C Pic

Please excuse the scruffy wiring etc, this is just a lash up to see how it sounds. The PS was from my AKSA55N and the case is certainly no virgin!
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Old 8th February 2008, 10:05 AM   #44
Dave S is offline Dave S  United Kingdom
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Close up....
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Old 8th February 2008, 03:13 PM   #45
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Right i have attached my boards to the psu and am trying to measure the bias. But the meter gives a zero reading. Even stranger the voltage across the two meter leads read by another meter is 50ish volts. What am i doing wrong?

Any ideas very gratefully recieved
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Old 8th February 2008, 05:32 PM   #46
brianuk is offline brianuk  United Kingdom
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Fill,

First things first, stop, turn all off and take a step back. Then without us influencing you draw us a diagram of exactly what you are doing, or link if you have one. Dont want to break anything, especially you, though it will cure your cold

Both yourself and Dave, nice looking work there

Brian
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Old 8th February 2008, 05:41 PM   #47
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Did just that, i was getting stressed which is always when things go wrong. So i sat and watched two ebisodes of 'The Long way down' which sort of chilled me out.

Well i am 99% sure my psu is cool, i have got twin secondary windings going into 2 bridge rectifers. The plus of one is tied to the minus of the other as per :-

http://www.tnt-audio.com/clinica/ssps2_e.html


I have got a 22,000 uf between each rail. This gives me a +37v and a -37v in comparison to the tied togther zero rail.

All this is working fine.

My issue is i have never measure current apart from using a clamp meter at work. From what i have read i have to put the meter effectively like a fuse in the +37v rail. It appears i blew the fuse in the metre on doing this i dont know why.

Any steps i should do or avoid whislt trying to measure the bias current?

Many thanks,

Fil
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Old 8th February 2008, 06:12 PM   #48
brianuk is offline brianuk  United Kingdom
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OK, it sounds like what you are doing is right, connecting all the amp up, remove the positive supply to the amp boards and then connect the meter in series.

A few gotchas here though!

1) have the meter on Amps
2) make sure the leads are plugged into the amp sockets on the meter and not voltage
3) nothing should be connected, no input or output form the amp

I have blown a fuse on one of those little yellow meters (200mA MAX) before (goes off nice and bright). If you are sure what you are doing is right there might be something wrong on the boards, ie a short of some sort, but if you are set to current on the meter and plugged in right it should be ok.

Get it plugged in and post up a photo or two of the meter and where the wires go before you turn on and we can look at it. Im being totally selfish I want a review.
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Old 8th February 2008, 06:17 PM   #49
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Ok fuse switched i have one channel working at 38 mA which seem fine, however dc offset is 0.09 vwhich seem too high, will this be an issue and if so how can i reduce it?
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Old 8th February 2008, 06:19 PM   #50
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If I get these bugger working there will be a review tomorrow for sure. My Psu could be a bit more sophisitacted but i think its good enough to get a decent idea what they are gonna be like.
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