No, there is no such USB header.

ejn63,

I uploaded the picture of the Optiplex 390 DT/MT motherboard. It shows #9 as the Internal USB Connector (USBF1) ?

Thanks so much!!  

I honestly do not know how I missed it.  I was looking at this manual too before and completely did not see that page.  Not sure how that happened, but now I know.  

Thank you very much for a pointer!  Now its time for me to open the desktop up again to see if those ports are availalble or not.  

Thanks again!! 

Thanks so much, @DELL-Alasdair R!!  

I honestly do not know how I missed it.  I was looking at this manual too before and completely did not see that page.  Not sure how that happened, but now I know.  

Thank you very much for a pointer!  Now its time for me to open the desktop up again to see if those ports are availalble or not.  

Thanks again!! 

The 390 uses the same 10 pin FLEX BAY connector as Many others in the Series. 

0GH483 Compatible with Dell Computers:
Dimension 9200, Dimension 9200 XPS 410, Dimension E520, Dimension E521, OptiPlex 740, Optiplex 740 Desktop, Optiplex 740 Mini-Tower, OptiPlex 740 MLK, OptiPlex 740e, OptiPlex 745, OptiPlex 745 Desktop, OptiPlex 745e, OptiPlex 755, OptiPlex 760, Optiplex 960, Precision T3400, Precision WorkStation 390, Precision WS390, XPS 410, XPS 420, XPS 430, XPS 730
Dell Digital Media Card Reader Drive With Rails for
Dell Computers 5150C 620SFF 740 SFF 745SFF 531C 530C
13 in 1 Card unit
Fits selected Dell Dimension Dell Inspiron and Dell Optiplex
with 10 pin Mother Board Plug Interface

 Dell P/N:JJ162 & FD746 & TW036
 Dell Digital Media Card Reader BlueTooth Drive With Rails Or Pins for Dell Computers
 13 in 1 Card unit With BlueTooth
 Fits selected Dell Dimension Dell Inspiron and Dell Optiplex with
 Mother Board Plug Interface Inc XPS Systems & Precision Systems
 Dell P/N:XR947 DU172

 Dell Digital Media Card Reader for Dell Optiplex
 19-in-1 Media Card Reader
 Fits selected Dell Optiplex 740,760,780 960 Series
 Dell P/N: 2VP58
 Dell ca-400 Media Card Reader. No Cable.
 Dell Digital Media Card Reader Drive 13 in 1 Card unit
 Fits selected Dell Studio M/T card reader and includes flex bay cable T748G
 Dell P/N:M810G
 Dell Digital Media Card Reader Drive 13 in 1 Card unit Inspiron
 13-1 Media Card reader and cable for inspiron 545 546 Studio and Dell MT & LMT Machines
 Dell P/N:CDM2D W812M
 Dell Digital Media Card Reader Drive With Rails Or Pins for Dell Computers
 13 in 1 Card unit
 Fits selected Dell Dimension Dell Inspiron and Dell Optiplex with Mother Board Plug Interface Inc XPS Systems & Precision Systems
 Dell P/N:1930930b01
 TH661 HD273 M7502 KD104 XN068 GT399 WY345 C9152
 Dell Digital Media Card Reader Drive With Rails Or Pins for Dell Computers
 13 in 1 Card unit
 Dell Media Card Reader for Studio XPS 7100
 Dell P/N:KK9PN
 Dell Digital Media Card Reader Drive With Rails Or Pins for Dell Computers
 10 in 1 Media Reader Card Unit
 Internal card reader for Inspiron 545/560/580 MT
 Dell P/N W812M
 Dell P/N PTXF7

 Vostro 230 MT Card Reader Including Cable.
 Model: I/O Interconnect R-680-070-215A-2
 Dell P/N X776R
 Dell Media Smart Card Reader Assembly including cable for Studio XPS 8000/8100
 Also fits other Studio Models Check Part N0.

 Dell P/N: H323J
 Media Card Reader Board (inc. cable) for Studio XPS 435T/9000
 (Note ths model fits into the existing carrier in your chassis )
 Also fits other XPS Non Bezel Models Check Part N0.
 Dell P/NSmiley Very HappyM691-FS YR887
 Card Reader with bezel for XPS 420 CAB-200 With Bluetooth
 Also fits other Studio Models Check Part N0.

 

Thanks very much!! 

I found that connector with your and everyone's help!

390 motherboard

390

Does anyone know the pinout for the 16 pin Front I/O header?  Like the Power SW +/- , the HDD activity light, etc.? Thank you in advance for any help.

None of these things are documented.

Its not wires to LEDs its wires to boards.

DELL DOES NOT DOCUMENT THIS like others do

https://www.intel.com/content/www/us/en/support/articles/000005643/boards-and-kits/desktop-boards.html

front audio and USB and diag led