Re: Further Adventures with the 9595 Power Supply...


"William R. Walsh" wrote

As you might know, I've been frustrated by the mysterious failure of the Delta 335 watt power supply that is used in the Server 95 and some Model 85s. More than anything else, I've wanted to know "why". To date I still do not know anything more than the TL494 controller IC is being "told" to shut the power supply down.

Well, I threatened a long time ago to try one 220/240 volts AC to see if would come to life. My hope was that maybe I could narrow the fault down to something specific in the 110/120 volt circuitry. What I didn't know was how I would arrange a circuit suitable for the 220 volt test.

Today I found a moderately sized step-up transformer in a junk box. Plugged it in and found it worked well enough to try a known working PC power supply on its 220/240 volt setting. So I grabbed one of the dead supplies and hooked it up. The filter capacitors charged up when I plugged the transformer in, but that was it. I hooked up a dummy load (a dead hard drive that would still spin up) and shorted pins 1 and 2 on the planar connector. Nothing at all happened.

So the fault is seemingly operating voltage independent...and on the supplies I've tried, the operating voltage is selected manually using a switch.

William

William

Try to look for bad capacitors ...

I have repaired alot of switchmodes - Not the PS/2 one.
90% of the faliures with the switchmodes were because of bad capacitors... You can't visualy see they are bad..

And the switchmode simply noy start.. Last time it was a PSU in my TFT monitor and it were a 10 uF/25 V capasitor there were dead..

/Niels







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