Help determining smd diode polarity in circuit

[Salvador12]

So I have the following problem, there is a ventilator using BLDC motor 3 phase which is drive by electronics on a single board, IC's and fets etc.
There is a speed control circuit not directly connected to the main board but instead "talking" to the board via optoisolators.
This board as a +10volt output pin, and then it has ground pin and A+ and B- pins for what I understand to be a variable speed control input via low voltage.
The problem is in this low voltage input circuit someone added a too high voltage and the input protection diodes are blown out.
I have attached a schematic of how those diodes are connected but they are SMD type and some "noname" brand so there are no real readable markings or any other signs just a small black package.
Can you please help me figure out the polarity based on how they are arranged in the circuit, overall there are 3 diode.
Please see attached picture.

 

[KlausST]

Hi,

why don´t you show a photo?

Klaus

 

[Salvador12]

Hi,

why don´t you show a photo?

Klaus

A photo of what? The actual board? My cam is not that good and the traces are so small i'm afraid it won't be of any help

 

[BradtheRad]

It's feasible to have your cam look through a magnifying glass at the board. There should be a position where you obtain a sharp image.

To focus, the cam might do so automatically, or else you turn a ring around the lens by hand.

 

[D.A.(Tony)Stewart]

The diodes would be used to prevent the input exceeding either voltage rail but show no current limiting R.
Thus they are normally reverse biased so the top has cathode (bar) to A+ and lower has anode to B-

 

[Salvador12]

The diodes would be used to prevent the input exceeding either voltage rail but show no current limiting R.
Thus they are normally reverse biased so the top has cathode (bar) to A+ and lower has anode to B-

That was also my initial guess since given it's a low voltage input for motor control I would se no reason why they would put those diodes in that order in a way that would conduct current under normal operation as it would short circuit the input above 0.7 or thereabout volts.