Anoma ASPR0515

[CapLeaker]

This is another Nortel 3x8 power supply made by Anoma exclusively for Northern Telecom. Dual voltage, first rail 5V, the other rail is 15V.

This thing has a weird problem. It powers up, but only supplies half the voltage on both rails. 5V only has 2.6V. The 15V rail has 8.1V
U3 = 10358 (dual ground sense amplifier?)
U2 (next to the opto) = TL431

Now as soon as I kill the AC, the voltage on the 2 output rails jump up to what they supposed to be, then fall off to zero V (bleeder resistor).

Nothing sticks out, no shorts on the output if I take the bleeder resistor R9 out.
So far I am guessing there is something wrong with the feedback circuit. Any help is appreciated.

[stj]

Re: Anoma ASPR0515

something is not bolted to the sink.

what controller does it use?

[CapLeaker]

Re: Anoma ASPR0515

That thing not bolted on the sink is a double diode. I thought it was bad, but it wasn't. That's how I found the bleeder resistor R9.
U1 (TO220 package) is on that heat sink sandwiched between it and the transformer. I have no idea what it is. I can't read it, so I have to take it out. Whatever U1 is. center pin is GND right to the main filter cap.


O.k. I found the problem and I fixed it. Bad 22uF 50V capacitor on C21. On picture #1, top left corner. There is a bigger capacitor and between it and the heat sink is then a smaller capacitor (C21). On the picture you can see like half of the capacitor. It has something to do with the feedback circuit, as the TL431 is there.

So all is good and voltage rails are up and healthy.