Codegen 350XA supply

[milesy]

Re: Codegen 350XA supply

thanks Rievax yep i have an isolation TXFR for that........based on your comments are you suggesting that the caps are bad so excess ripple is coming through the main tfxr and mucking up the regulation?

[rievax_60]

Re: Codegen 350XA supply

A faulty 470uf-200v capacitor might explain the messy 12v cathode waveform. There could be a 100Hz amplitude ripple on the waveform that the CRO might not show us while set to a fast timebase.

[b700029]

Re: Codegen 350XA supply

ok thanks rievax ....well now im scratching my head....for sure on my unit the cathode is definatley double the anode so yes its passing both cycles however i thought that the flat section between each peak looks wrong......

The flats will vary in width to maintain a constant 12V average on the output filter caps, as the load varies.

If you're going to try measuring the primary, remember to float the DUT with the isolation transformer, NOT the scope.

[Escort Eagle]

Re: Codegen 350XA supply

I have not used 450V capacitors ratings before . I have always used 200V ratings . So, I am not sure Double Capacitors of 450V ratings are safe here or not !! Do it at your own risk !!

[milesy]

Re: Codegen 350XA supply

hi escort - why would you think that using 450v caps would be an issue?? i cant see a problem using a higher rated cap?

[milesy]

Re: Codegen 350XA supply

The flats will vary in width to maintain a constant 12V average on the output filter caps, as the load varies.

If you're going to try measuring the primary, remember to float the DUT with the isolation transformer, NOT the scope.

should have said got the flats detail thanks

why the importance of having the DUT floated instead of the scope?

[tom66]

Re: Codegen 350XA supply

If you touch the isolated scope you will get a live-earth short which will hurt a lot.

[milesy]

Re: Codegen 350XA supply

If you touch the isolated scope you will get a live-earth short which will hurt a lot.

ahhhhhhhhhhhhhhhhhhhh

[c_hegge]

Re: Codegen 350XA supply

I have not used 450V capacitors ratings before . I have always used 200V ratings . So, I am not sure Double Capacitors of 450V ratings are safe here or not !! Do it at your own risk !!

hi escort - why would you think that using 450v caps would be an issue?? i cant see a problem using a higher rated cap?

It won't be a problem, other than that 450V rated caps may not fit, as they will be physically larger.

[Escort Eagle]

Re: Codegen 350XA supply

Hi, c_hegge how are you ? I know you . We talked many times . May be not this place, May be somewhere .

And milesy What is the result dude ? We are expecting for your result .

Thanks

[milesy]

Re: Codegen 350XA supply

ok a strange state of play ..........lol (cant beleive this)

it seems that perhaps afterall there may be something wrong with the motherboard i was using for testing - to explain.

As of now......i plug the 20 pin ATX connector in to the MB and turn the PS on by shorting the green wire to ground. So at this point the PS turns on and the 12V is reading 11.75v - so great you say all is good.....but when i plug in the 4 pin connector the MB voltage drops to 10v and eventually the wire i have soldered to the regulator diodes melts of........woops so presumably there is a short on the MB.

so i took a 50W 2 ohm resistor and connect it to the 12v line of the PS (leaving the 4 pin connector off the MB) - again turn on the supply and this time the voltage drops to about 11V.....connect the CRO (which now also seems to be playing up a bit GRR) and looking at the trace without the resistor connected its all over the place.....connect the resistor and i get a nice clean rectified waveform expect for a large spike on the leading edge of the trace (see below) - oh and i should add this is without any addition caps connected on the front end - add the caps on the primrary and there is little if any change...


so im back to square one here and completely confused.



IMGP9588.jpg by Adrian Miles Photography, on Flickr

[c_hegge]

Re: Codegen 350XA supply

Hi, c_hegge how are you ? I know you . We talked many times . May be not this place, May be somewhere .

Huh? Are you sure? The only members I have anything to do with outside here are Ratdude747 and Shovenose.

[milesy]

Re: Codegen 350XA supply

back to more important issues

what are your thoughts on my supply hegge

[c_hegge]

Re: Codegen 350XA supply

I'm still thinking try another rectifier if you haven't already done so. those two diodes on the bracket can only deliver about 6A combined. Any PC with a 4 pin CPU connector should have at least double that available, or more of it's a power hungry CPU.

[milesy]

Re: Codegen 350XA supply

the specs on the PSU say 12v 15 A....trying to find the data sheet for the diode to check the current capability

[milesy]

Re: Codegen 350XA supply

so the diodes are FR502 which according to the data sheet have a current capability of 5 Amps each - so realisticly i should be able to drag 10 A out of this supply

having a closer look at the wave form above and the picture shown above is with the CRO set at 2v/div and DC coupled.......doesnt that trace look a little small from what it should be if you refer back to rievax post on page 2 the trace he put up is with his CRO set on 20v/div........

if we assume the diodes are ok (as they test ok and seem to pass the voltage ok) then can i presume that the signal coming from the actuall transformer is too low???

[c_hegge]

Re: Codegen 350XA supply

Ah, I didn't realise you had 5A diodes. they are usually only 3A. But still, 10A is insufficient.

Anyhow, if you're sure the diodes are OK, then you could have a bad winding somewhere on the transformer.

[milesy]

Re: Codegen 350XA supply

ok looks like this one has me beat......ill move on to the next one - hope you guys can lend me some advice with this one

[b700029]

Re: Codegen 350XA supply

but when i plug in the 4 pin connector the MB voltage drops to 10v

Has this supply ever powered the mobo successfully? The 4-pin connector is +12V for the CPU buck converter and draws a lot of power.

[rievax_60]

Re: Codegen 350XA supply

My 350XA is a bit different. It has a F16C20 for the 12v rectifier. Its a TO-220 case 16A total dual fast silicon diode.
Silicon diodes take a small amount of time to turn on and off but this doesn't fully explain the large size of the spike.
It might be useful to see anode and cathode waveforms loaded and unloaded to see how much the amplitude changes. But its seems that the 12v rail is just being overloaded.