On examination with my Carson Magnivisor ... different light angles revealed
Q4 might be
4405
BD351C

 

1 Open (No Beep)
0 Closed (Beep)
-----------SW--JP3
From__1 2 3 4 1 2
U8-1__1 1 1 0 1 1
U8-2__1 1 1 1 1 1
U8-3__1 1 1 1 1 1
U8-4__1 1 1 1 1 1
U8-5__1 1 1 1 1 1
SW1__0 1 1 1 1 1
SW2__1 0 1 1 1 1
SW3__1 1 0 1 1 1
SW4__1 1 1 0 1 1
JP2-1_1 1 1 1 1 1
JP2-2_1 1 1 1 1 1
Q4-1__1 1 1 1 0 1
Q4-2__1 1 1 1 0 1
Q4-3__1 1 1 1 0 1
Q4-4__1 1 1 1 1 1
Q4-5__0 1 1 1 1 1
Q4-6__0 1 1 1 1 1
Q4-7__0 1 1 1 1 1
Q4-8__0 1 1 1 1 1

I believe this is correct.
Will have to return later to check again.

 

Thanks. That is ok so far.
Please include HD-1, HD-2, HD-3 in the above list.

 

1 Open (No Beep)
0 Closed (Beep)
-----------SW---JP3---HD--
From__1 2 3 4 - 1 2 - 1 2 3
U8-1__1 1 1 0 - 1 1 - 1 1 1
U8-2__1 1 1 1 - 1 1 - 1 1 0
U8-3__1 1 1 1 - 1 1 - 1 0 1
U8-4__1 1 1 1 - 1 1 - 1 1 0
U8-5__1 1 1 1 - 1 1 - 1 1 1
SW1__0 1 1 1 - 1 1 - 1 1 1
SW2__1 0 1 1 - 1 1 - 0 1 1
SW3__1 1 0 1 - 1 1 - 1 1 1
SW4__1 1 1 0 - 1 1 - 1 1 1
JP2-1_1 1 1 1 - 1 1 - 1 0 1
JP2-2_1 1 1 1 - 1 1 - 1 1 1
Q4-1__1 1 1 1 - 0 1 - 1 1 1
Q4-2__1 1 1 1 - 0 1 - 1 1 1
Q4-3__1 1 1 1 - 0 1 - 1 1 1
Q4-4__1 1 1 1 - 1 1 - 1 1 1
Q4-5__0 1 1 1 - 1 1 - 1 1 1
Q4-6__0 1 1 1 - 1 1 - 1 1 1
Q4-7__0 1 1 1 - 1 1 - 1 1 1
Q4-8__0 1 1 1 - 1 1 - 1 1 1

 

Ok. I think we are finally getting somewhere.

We are going to focus on the ON/OFF switch.
Make certain that the connector into SW can only be inserted one way.
Remove the connector from SW socket.
Using the same pin identification as shown for SW, determine which pins are connected when the switch is in the ON position.

 

Also, see if you can find out what is connected to SW-3.

 

Ok. I think we are finally getting somewhere.

We are going to focus on the ON/OFF switch.
Make certain that the connector into SW can only be inserted one way.
Remove the connector from SW socket.
Using the same pin identification as shown for SW, determine which pins are connected when the switch is in the ON position.

Probes Inserted in Small Openings above SW Numbers
— Red SW1 and SW2, Yellow SW3 and SW4 continuity
O No continuity between SW1 and SW2, SW3 and SW4

 

Also, see if you can find out what is connected to SW-3.

FB5 is connected to SW3
If Switch is closed, SW3 (via SW4) would connect to U8-1
Continuity is also across FB5
Fuse suspect?

Power In (end of Receptacle) has continuity to JP3-2

With power connected ... Power shows up to right of Receptacle In Half White/Half Red Circle on Red side solder through hole.
Ground Black Probe on Left/Red Probe on Right shows 12V.

 

Is there any possibly that the HD connector and the SW connect can be plugged in backwards?
I would expect that the connectors are keyed to prevent improper connection.

(Apologies ... I just saw this question)
Each plug has a specific shape that only snaps in one way.

Also realize I'm not answering all connectivity questions in an orderly fashion ... This is my first circuit board reverse engineering in such detail.

There is also a curious red marker mark on the HD plug, and a rubbed off one on the LED plug. Maybe just Inspection marks?

 

Post #24 seems to suggest that there is continuity between the +12V input on the power connector and pins 1,2 & 3 (I think) of Q4 via JP3
Post #26 seems to show continuity between Q4 pins 5,6,7.8 (I think) and sw1 connector pin. (This agrees with the tables in posts #42 and #44)
I think Q4 is a power mosfet in a package similar to an FDS8896 but I think it will be a P channerl device. I think this is being used to switch the 12 volt input. So maybe my comment in post #19 is correct. The argument against this theory is that connector pin SW1 is shown with a red wire connected to it which you would normally expect +5 volts. I think these continuity readings need to be rechecked. (Preferably using a much lower value of resistance than 30 ohms that billy is using to define continuity. I suggest 1 ohm if billy is correcting for test lead resistance or 2 ohms if he is not.)

Les.

 

Jumper JP3 was removed during the measurements in #(42)44.
Earlier measurements, JP3-1,2 was connected.
Continuing to use 30 ohms as cutoff, rechecking:
JP3-1 is on Q4 side, and has continuity with Q4-1,2,3
JP3-2 is on Receptacle side, with continuity with the 12V Receptacle pole
Continuity between Q4 pins 5,6,7.8 and SW1 connector pin

Aa far as I know, my Extech minitec24 meter doesn't have the option to reduce resistance below "about 30 ohms"
See bottom of page 4
https://www.allaboutcircuits.com/test-measurement/multimeters/extech-mn24/manual/
Resistance measurement (same page) goes down to "200 ohm range".
I would need to find a meter if we need to measure continuity indicated below 1 or 2 ohms, and/or to consider correcting for test lead resistance. Suggestions welcomed.

 

We are getting to the bottom of this. I have been fooled by the colors of the cables going to SW.
I have to read over all the previous posts to see if this makes sense.

12VDC power goes from J1 to JP3 to Q4 (which is a P-channel MOSFET switch) to SW-1 to SW-2 to HD-1 (yellow).

SW-3 goes to SW-4 to U8 (5V buck supply) to HD-3 (red).

What we don't know is what is connected to FB5 going to SW-3.
Somewhere FB5 must be fed from a 12VDC connection.

(We could jumper across the 12VDC feeds but I would prefer to find out first what is feeding FB5.)

 

Currently investigating Continuity with 12V Receptacle pole ...

Rechecking these:
With JP3-1,2 Jumpered, there's no "30 ohm" continuity with the 12V Receptacle pole and SW or HD ... but the Display "flashes a value" for SW-4 and HD-2,3
No flash for SW-3,2,1 or HD-1.

 

Where does this connection from FB5 go?

 

Looks like FB5 communicates with USB2?
Top View with faded path from Bottom View showing path match FB5 and USB2 area

 

Are they feeding U8 (SI-8050JD) from the USB?
That would make some sense. However the SI-8050JD needs 7VDC minimum to output 5VDC.
Something has to feed FB5 in order to generate the 5VDC required by HD-3.
Maybe U8 is a buck-boost converter getting power from USB 5V.

 

I don't think this enclosure is "USB2 Powered".

It has HD data transfer by either FW or USB2 but the manual says one or the other can be connected, not both.
So ... that eliminates "USB2 powered"?

The 1 LED light will flicker when data is being read or written. Steady when idle.

It has to decide which path is being used for data transfer: FW or USB2.

I could reassemble the enclosure with a hard drive installed, and see if it powers on with a USB2 connection to my computer.
But ... I remember it did not before ... but I am willing to test again.

RED is 5V ... YELLOW is 12V?

 

Have you attempted to use the drive with a USB connection to the computer?

Here is a simple test.
Install JP3.
Install SW connector.
Omit HD connector.
Install 12VDC power adapter.
Connect USB cable to computer.

Measure voltages from GND to HD-1
and GND to HD-3.
(Use the mounting holes as GND.)

We don't know as yet if the USB driver must be properly initialized, recognized, and activated for the HD power to be enabled.

Edit: You typed while I was typing.

Normally, RED is +5VDC and YELLOW is +12VDC.
But the colors at SW are not normal. That is what led me astray. I had assumed, incorrectly, that they were switching the +5V and +12V lines.

 

I will set up the enclosure and test as you suggest here.

Just in from macsales.com (OWC: Other World Computing) folks where I got the drive:

Unfortunately we arent able to help with repairs for the boards of our products, however, I can tell you that our Elite Pros were never bus-powerable and require an AC power adapter to operate. I hope that helps.

 

Have you attempted to use the drive with a USB connection to the computer?

Here is a simple test.
Install JP3. No
Install SW connector.
Omit HD connector.
Install 12VDC power adapter.
Connect USB cable to computer.

Measure voltages from GND to HD-1
and GND to HD-3.
(Use the mounting holes as GND.)

We don't know as yet if the USB driver must be properly initialized, recognized, and activated for the HD power to be enabled.

No voltage measured.
Also our USB bridgeboard doesn't appear in my Apple Profiler.
I tested the cable with another fully functional enclosure and it is good.

12V tests fine to the end pole of the receptacle and JP3-1,2 (Jump-ed) and Q4-1,2,3. Q4-4 measured 10.4 Volts?