Codegen 350XA supply

[Escort Eagle]

Re: Codegen 350XA supply

Escort Eagle, he's not going to get anything to work with the 12V rail at half its nominal voltage.

12V is dropping to 6V at loaded condition . At normal state it is showing 11V . Now First I need to know - Is the Display is showing or not . This Display's presence or absence will separate the problem of voltage dropping . This Display's presence or absence will tell you - why the voltage is dropping - Is it for Primary side or Secondary side . Display's presence or absence will identify that . This is why - I need to know Display's presence or absence First .

Thanks

[kaboom]

Re: Codegen 350XA supply

While you're at it, replace the small ceramics in the RC snubbers on the secondary side.

Had one of these junkers where on of the 10 ohm resistors in a snubber was totally incinerated.

It was under some unburned dust, so I think the ceramic cap shorted shortly after the supply was first used, with the dust building up over the (short?) life of the system.

[c_hegge]

Re: Codegen 350XA supply

^
The single diode is for the 5vsb. I was referring to the 12V rail before. Admittedly, putting the 5vsb diode on the heatsink is a much more sensible option than Bestec and Delta putting it next to the 5vsb input cap. Who would have thought that Codegen could do better than Bestec and Delta?

[b700029]

Re: Codegen 350XA supply

Escort Eagle, he's not going to get anything to work with the 12V rail at half its nominal voltage.

Diodes on a bracket!!

Replace the two diode-bracket with a proper rectifier. one of them could be toast

You mean diode on a bracket

...The possibly only advantage of building it this way is so you only need to replace one diode instead of a 2-diode pack...

[Escort Eagle]

Re: Codegen 350XA supply

OK. It generally happens when the Output caps are gone Bad or when Caps Pins soldering with PCB gone bad . I hope you have no output Badcaps and Bad soldering because you have tried those method already .

Now you connect the Power supply with Motherboad and tell me is there any Display in Monitor ?? If I am not wrong, then the power supply has no display . Please ensure me this power supply has display or not .

Thanks

[rievax_60]

Re: Codegen 350XA supply

Ok so if the assumption is correct i should be able to hook the Cro up to the anode of the regulating diodes and see a trace basically the same but alternate polarity on each anode??

With the power supply lightly loaded, on the diode anodes there should be a stepped square wave. It alternately pulses negative and positive with zero volt dead times in between.
It should look exactly the same on each anode, but 180 degrees out of phase.
If both diodes are working, there should be a square wave of double the frequency at the common cathodes(middle pin). The bottom of this square wave should not go more than about a volt negative.

[milesy]

Re: Codegen 350XA supply

Ok so if the assumption is correct i should be able to hook the Cro up to the anode of the regulating diodes and see a trace basically the same but alternate polarity on each anode??

[c_hegge]

Re: Codegen 350XA supply

Thanks I will recheck..am I right in saying the symptoms definitely seem to be only getting half of the cycle through to the 12v line?

Sounds about right to me too.

[rievax_60]

Re: Codegen 350XA supply

Thanks I will recheck..am I right in saying the symptoms definitely seem to be only getting half of the cycle through to the 12v line?

Yes, I can't think of any other possible reason.

[milesy]

Re: Codegen 350XA supply

Thanks I will recheck..am I right in saying the symptoms definitely seem to be only getting half of the cycle through to the 12v line?

[rievax_60]

Re: Codegen 350XA supply

I have seen axial diodes go intermittent open, very rare though. You might pick it by a fluctuating meter reading while the diode is being gently flexed.
Cracked solder joints can be difficult to spot. Maybe you should check some more like at the transformer pins and the bracket the diodes are soldered to and just try the power supply again.
There should be continuity between the pads that the diode anodes solder to. The path is through the secondary winding.

[milesy]

Re: Codegen 350XA supply

You think the diodes could be faulty under load even though they test ok with a DMM??

[c_hegge]

Re: Codegen 350XA supply

Diodes on a bracket!!

Replace the two diode-bracket with a proper rectifier. one of them could be toast

[milesy]

Re: Codegen 350XA supply

thanks guys..........well as i didnt have any replacement caps i thought i would investigate the open diode caper.......it made sense given that the 12v under load was only reading 6v - and if one of the diodes was open the 12v output cap would only get half the amount of power rather than both +ve and -ve pules.....

so i removed the heatsink that contains two diode packs (S20C40C) and 3 discreet diodes (photo below) unfortunatley all seems to be ok with this lot of components...removing this does allow me to see a little better though and there is still no obviously bad caps.

if there are bad caps - am i likely to be able to test them somehow???


IMGP9564.jpg by Adrian Miles Photography, on Flickr

[rievax_60]

Re: Codegen 350XA supply

HI Guys

hoping to get a bit of guidence here...i have the above PSU which stopped working a while back.

Purple Wire has 5v
Green Wire sits at 4.3 volts before startup

With only the 24way ATX plug connected i can press the start button and the PS starts giving 5.38v on the red and 3.3V on the orange, however on the yellow wire i only get 11.0V

If i plug in the 4 way (yellow + black) to the MB the yellow wire drops to 5.27v and the red wire INCREASES to 6.72V......its not the MB as another supply works fine.....any ideas where i start ??

Adrian

There might be one phase missing at the 12v rectifier.
Check for any bad solder connections from the transformer secondary to the 12v diodes, like solder cracks at the diode pins.
Also check for any open diodes

[c_hegge]

Re: Codegen 350XA supply

As I suspected, it has HEC Caps. Try replacing them

[milesy]

Re: Codegen 350XA supply

anyone?

[milesy]

Re: Codegen 350XA supply

yep photos i can do..........


IMGP9561.jpg by Adrian Miles Photography, on Flickr


IMGP9562.jpg by Adrian Miles Photography, on Flickr


IMGP9563.jpg by Adrian Miles Photography, on Flickr

plus i think i found the schematic of the supply........


codegen_atx_300w_m by Adrian Miles Photography, on Flickr

[selldoor]

Re: Codegen 350XA supply

i realise its a bit hit and miss without being able to see the supply

How about some clear well focussed no flash pictures then?

[c_hegge]

Re: Codegen 350XA supply

Knowing Explodegen (Codegen), the caps are probably HEC brand (which stands for Horrible Electrolytic Capacitor). Like any junk cap, they can go bad without visibly showing it, but yes, it is also possible that the problem is elsewhere.