ATX 300 12E dead

[rayxoxo]

Found C36 reading 4.3ohms and slightly bulging. No schematic and just guessing at this time. Replaced c36, but still nothing. Any hints? This PSU came out of an older Gateway.
Schematic might be helpful.

TIA

[CapLeaker]

Re: ATX 300 12E dead

probably there are more caps bad. Any pictures? Caps still can be bad and look good from the outside.

[everell]

Re: ATX 300 12E dead

Measure 5vsb on the purple wire. Should be 5 volts +/- 5%. If not, your power supply will be dead.

[everell]

Re: ATX 300 12E dead

Here is schematic of Bestec 5vsb circuit which should be very similar to yours.

[rayxoxo]

Re: ATX 300 12E dead

Firstly thank for the schematics - I now have 5v on the purple output lead - No fan or other voltages, no 12s, 3.3, etc.

Will slowly check out the other caps, etc. Any short cut suggestion appreciated.

[everell]

Re: ATX 300 12E dead

Check for shorts on switching transistor and output diodes. Does fan show slight movement when you first turn on the power supply? The other capacitor forming the pi output filter on the 5vsb should also be changed. Bestecs are notorious for having lots of glue which goes conductive and causes resistive paths. Remove as much glue as you can, especially any that has turned brown or black.

[rayxoxo]

Re: ATX 300 12E dead

Fixed - replaced C36/2200uf 10v. Also fan was stuck - Had an item laying loose preventing the fan blades from turning. How it happened is still a mystery but it must have been the heat originally. Though these are noted for the C36 going south, from the post on this forum.

Thanks all for the help.

Ray

[RJARRRPCGP]

Re: ATX 300 12E dead

Bestecs are notorious for having lots of glue which goes conductive and causes resistive paths.

Looks like the same thing with CWT.
My 2003 True 430 has the dreaded brown glue.