Pegasus2 R4 Mounting Issues on MacOS 15.2

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Ben Broad posted this 08 January 2025

I have a Pegasus2 R4 unit.

It works on my 2018 Macbook Pro, but not on my 2024 Macbook Air (M3, MacOS 15.2). 

I am connecting it via a Thunderbolt 2 to Thunderbolt (USB type C) connector. 

I followed the instructions published at https://kb.promise.com/thread/installing-the-macos-pegasus-dext-driver/ 

I ran systemextensionsctl list | grep pegasus which returned [activated enabled]

The drive mounts briefly and I can see the files. It unmounts after about 20 seconds.

While troubleshooting I noticed the Thunderbolt cable was very hot at the drive unit end. The drives remained lit up (blue) after the cable was disconnected and remained so until I removed power.

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R P posted this 08 January 2025

Hi Ben,

The usual suspects in cases like this are...

  • A bad or intermittant Thunderbolt cable.
  • The power supply is going bad.

The cable is easy to test, try another cable.

The power supply is a bit more difficult. One test is to power down the Pegasus, remove the power cable, then unseat all the drives, pull them out maybe 1/2 inch leaving them in the same slot, then plug the power cable back in and see if the Pegasus will power up and stay powered up without the drives. If it does then the power supply is getting weak. Shut the Pegasus down and remove the power cable and re-insert the drives. Then plug the power cable in and boot it again. Sometimes after this test things work OK, so it's worth a try.

Note: Be sure that the Pegasus is powered down and the power cable removed before unseating or reseating the drives.

Ben Broad posted this 22 January 2025

Thanks RP.

I followed your suggestions and found, with drives removed, the Thunderbolt light would flash intermittently, and on occasion the blue light would change to red. This would also happen when the cable was plugged into the other port on the Pegasus. I am seeking a new Thunderbolt 2 cable to test.

Ben Broad posted this 2 weeks ago

The unit no longer turns on. I had a look at the power supply (FSP250-50LC) and did a search for a replacement. There seems to be a number of them with different wiring/connectors. Is there an exact part number for a replacement unit?

Thanks.

R P posted this 2 weeks ago

Hi Ben,

Sorry, we have no information on the power supply.

Over the years other forum posters have found replacement power supplies and posted of their success, but I don't recall that anyone posted where they found it and what the part number was.

Another solution is to find a used Pegasus chassis. You can try EBay, Amazon, google shopping and even a local computer store.

Currently the Promise Shop has some refurbished Pegasus R4's for sale. This would work.

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