Posted by RvdH under Computer & Peripherals on Jan 03 2020

I recently purchased a Seagate Expansion Portable drive, actually i only purchased it to extract the 2,5 inch hdd drive inside for use with an Intel Nuc as prices for external enclosures with drives are much cheaper compared to internal drives sold separately.
With the drive being fitted in my NUC system I only kept the PCB and usb cable that came with the original package.

Printed on the PCB: NEXPANSION_JMS577_2.5_REV0.1 
Product number: E157925

The PCB has a LED on it as you can see right above, but without the original box this seems non-functional using the original Seagate firmware (v00.07.01.00)
On this page i found alternative firmware that could be used with this PCB. The Jmicron JMS577 chipset seems to be a special, vendor specific chipset that is interchangeable with the standard Jmicron JMS578 chipset. The JMS578 is a USB 3.1 Gen1 to SATA 6Gb/s bridge controller that supports UASP and has TRIM command support if a SSD is used.

If you like to experiment with the optional parameters explained on that page I suggest you update the firmware using Linux, as i not actually have a use for this PCB i decided to simply try to use the windows updater i found and flashed the JMicron standard firmware to the device.

After flashing and power-off/on the device using the firmware found here the device no longer shows-up as being a [<<UASP>> Seagate Expansion] but now shows as [<<UASP>> JMicron Generic] USB to ATA/ATAPI Bridge. Even the LED light started blinking instantly with the extra benefit the overall performance off the chip is (a little) better using the JMicron standard firmware.

Old firmware
Benchmark done with Samsung 850 EVO 250GB on the PCB using the Seagate original firmware 

Benchmark done with Samsung 850 EVO 250GB on the PCB using the JMicron JMS578 standard firmware 
Last edited Jan 03 2020


I found new firmware on a recent unit

Posted by RvdH on Sep 19 2021 02:13
Hi thx. Ruud.

Yes well the comment of SEAGATE NL was: "We dont have spareparts" (as they are assembled in China).
Try a vendor....not the expected answer i hoped for :-(.
Ok will search for EBAY.



Posted by Peter SPanhaak on Sep 10 2020 15:48

You mean the PCB only?
A vendor other then Seagate themselves I do not know, but I have seen many eBay sellers that offer the Seagate JMS577 PCB

Posted by RvdH on Sep 10 2020 12:57
Does anybody know a vendor who sells this SATA6-USB3 ( NEXPANSION_JMS577_2.5_REV0.1 interface card ? Mine is broken, with "on and of" connection when connecting it to the -mini B jack to USB external cable.
Please assist.

Kind regards.

Peter Spanhaak

Posted by Peter SPanhaak on Sep 10 2020 12:49
This post is result #3 when I search for "jms577". A few years ago I bought some very cheap Seagate Expansion enclosures w/o HDDs from OWC, with F/W They reported the disk size as one sector smaller than the actual size, which upsets partitioning tools for already-formatted disks (it seems to be a recurring problem with USB/FireWire/etc. bridge chips for as long as they've existed). F/W reports the correct size, plus the activity LED now works (I'd wondered if it could be enabled).

Posted by chrstphrchvz on Aug 11 2020 23:50

post your comment

 (*) - required