I need an small external storage (4-6 3.5″ disks) for home server and initially was thinking about buying external disk enclosure with SAS interface. However despite the fact that they do exist, I was unable to find one for reasonable price. Just a case for 5.25″ costs around €80, so I decided to try make DIY external enclosure.
First thing needed is a drive cage, I’ve found that cages for ML310e/ML350e looks suitable and was able to buy one for around €50.
I got 674790-002 hot-plug version (686745-002 is not-hon plug version, I would pretty happy to get non-hot plug version but they were more expensive that one I got).
Looks like HP put something similar in HP Micro server gen 8 (at least caddy from microservers fits into cage):
The disadvantage of hot-plug cage is unknown pinout. It’s simple board, from my understanding it provides power for disks (without conversion) and data connection (without expander):
Here is power connector:
I used multimeter to just poke around the board and find traces from power to SAS power connectors, also I used photos of HP 822606-001 10 pin to 8 Pin connector, just to get a clue about 2 unknown pins.
Here is my findings:
Pin 1 – Unknown
Pin 2 – GND
Pin 3 – Unknown
Pin 4 – 5V
Pin 5 – GND
Pin 6 – 5V
Pin 7 – 12V
Pin 8 – GND
An interesting observation, pin 1 is not used by HP’s 10 pin to 8 pin adapter. Trace leads to small 2 pin connector and to component D2 (probably protection diode pair), which is close to Q1 ( transistor pair?) and U1 (most likely LDO).
Pin 3 – connected to an op-amp’s (TSV912AIDT) non-inverting input. That pin is used in 10 pin to 8 pin adapter (gray wire). That op-amp close to i2c EEPROM ATMLH602 and un-populated U5:
EEPROM’s i2c bus connected to un-populated U5, from which two traces go to SAS connector (sideband ?). I wonder why they left unconnected EEPROM on board? In that way HP will not be able to do their vendor lock or blackmail you into buying a subscription so that the equipment you bought will continue to work.
So I have no idea what is pin 1 for. It doesn’t look like power-on pin, because here is no power transistors. I have no idea what pin 3 is doing and why they need op-amp. It may be amplifier for thermistor for temperature monitoring, but again it makes little sense because pin connected to input of amplifier and it looks quite strange to use analog signal for that.
PS
One more curious observation, 3.3V on SAS power port are unconnected
PPS
EEPROM