What is this black item

[ALERTLINKS]

Essential protection is provided by including a diode in the output stage.
Flyback diode - Wikipedia, the free encyclopedia
From web pages,

Back emf Protection

The protection diode connected across the inductor is normally reverse biased, as the voltage on its cathode, connected to the +V supply rail, will be more positive than its anode on the collector of the transistor. At switch off however, a large voltage spike of opposite polarity appears across the inductor, due to the collapsing magnetic field. For the duration of this voltage spike, the collector of the transistor could be at a higher potential than the supply, except that if this happens, the diode will become forward biased and prevent the collector voltage rising any higher than the supply rail.

MOSFET as a Switch
Inductance
**broken link removed**
Transistor Help - All About Circuits Forum

If there is no paralell diode to motor, then this is 'this' diode.

 

[City fan]

After checking and giving board good clean, there is what looks like a zener symbol where our problem unit should go (sorry didn't give board good clean earlier).
Also on back of board there is the name "Alcon" followed by ECU 101 and ISS1, is this any help.
The circuit is my own work

 

[Raza]

Alcon is a famous Ophthalmic Pharmaceutical company. Their well known product is Contact Lenses (Alcon Ciba Vision). They also manufacture surgery equipment for Ophthalmology. The number you showed is the reference for the company product.

 

[City fan]

Thank you guys for your help, i'll take all info you've given and decide what item to try.

 

[tpetar]

Thank you guys for your help, i'll take all info you've given and decide what item to try.

Dont wory its zener diode 1,4W I think 8,5V try it give about 15V and see zener voltage. ;-)

 

[City fan]

Thanks:lol:

Did find site for Alcon electrics, now just capacitor manu.

 

[tpetar]

No I didnt, I told this based on expirience.