Antec PSU TP3-550 Question

[TXCritter]

I am trying to fix a computer from my son-in-law. When I tried to turn it on I got nothing, no PSU, CPU or case fan. I am told that it did work before I took it home. I checked the case power switch and it seems to be okay (continuity check) and also tried jumpering power switch leads. I have looked at the PSU and I am not sure whether it is bad or not. With the 24 pin connector jumpered on the green and black here is what it does:

1. The 12V PSU fan does not turn on and only shows 4.83V on its PSU connector. (Fan does work on Molex 12/5V connector using the 12V side).
2. The case fans will not run on Fan Only Molex connectors. Note: The Fan Only Molex has 1.66V with the PSU fan plugged into the PSU; it is 4.4V to 4.8V with the PSU fan unplugged from the PSU. Shouldn’t it be 12V all the time?
3. The other Molex connectors have 12/5V as normal whether the PSU fan is unplugged or not.

The PSU is an Antec TP3-550 and is out of warranty. At least it is now with the seal broken.

What is the thought about the power supply? Is it bad or do I have some other problem.

[Support@ANTEC]

Dear TXCritter,

I am not quite sure, where you are measuring the Voltage you are stating. The molex connectors should always have +12V on the yellow cable while +5V on the red. If these values are not correct, then something is probably wrong with the PSU.

If you opened the PSU, you have unfortunately voided your warranty that is correct.

If you give me a few more details, I might be able to help you out better. Especially on when and how you are measuring those values you stated.

Thanks and best regards,

ANTECsupport

[TXCritter]

I put a jumper (paper clip) between the green and ground on the 24 pin connector. With the PSU disconnected from the computer I recorded:

Molex Connectors (MC) – Measurement between the hot and the ground for both the 12V and 5V sides are 12V and 5V. At this point the case fans run when plugged into the MC.

Fan Only Molex Connectors (FOMC) – This model has FOMC’s (I found a FAQ that mentioned they were for speed/temperature control). No case fans would run when plugged into them. I measured across the FOMC (it only has 2 contacts) and recorded the following:

With PSU fan plugged into the PSU the FOMC measured 1.66V.
With PSU fan unplugged from the PSU the FOMC measured 4.4 to 4.8V

The PSU fan connection is the connection that in internal to the power supply.

My problem is that I do not know if the FOMC should exhibit this behavior and if it indicates anything about the condition of the PSU.

When I plug in the 24 pin connector and the CPU connector to the motherboard I do not get a light or anything. The MC and the FOMC show no voltage.

I obviously do not want to buy another PSU if the motherboard is damaged so I am looking for some guidance or best guess based on what I found. If I didn’t do enough testing please let me know what else to test and how.

Thanks

[Support@ANTEC]

Thank you for explaining in detail.

From what it looks like, the PSU is defective. The PSU fan should start of at just above 4V to get it at least spinning. It is hard to tell though, if your Mainboard is still OK as well. If you have the chance, please try to run it with a known good PSU to eliminate any other defective components of your computer.

The behavior of the Antec TruePower Trio PSU is not normal though, and it should be replaced.

Best regards,

ANTECsupport