Hello I have the card MC-66 with a diode D11 broken and I can not find the code and value. how can I? does anyone know the value / code?

thanks

MC-66 controller motor speed

D11 what value is it?? please!!! :'(

 

On the MC-60 the D11 is a LED?
Not sure what the differences are for the 66?
Max.

 

D11 is Diode Zener but I do not know what value/code is it?

thanks

leo

 

The MC-60 has a 1N742 for the 12vdc supply, most likely the same on the MC-66 as this is a typical way to produce the low voltage supply on these non-isolated drives.
Max.

 

thanks, but d11 is diode zener code ?... see photo

 

That should be 1n4742 for 12v zener, the reverse-engineered schematic showed 1n742 which is 150v.
Max.

 

It's unusual for a zener to have absolutely no markings or stripes.

Visually it looks to me like a DIAC, although I don't want to argue with Max as this is his area of expertise and he has schematics!

I am curious how the O.P. diagnosed the diode as "broken".

If it is a DIAC it will measure as bad on a typical multimeter diode test.

 

I don't have the schematic for the MC-66, just the MC-60, but it appears close, but the silk screen symbol on the board indicates a diode of some kind, I do have a stock however of the 1n4742 and they have the typical black stripe at the cathode end?.
Max.

 

How do you know the diode is broken? looking at the middle photo it says SCR trig, and an opto Moc3052 which makes me think its driving mains voltage to a Triac/SCR like this so i think it may be a diac or suppression diode.

 

Here is an old thread on a MC-66 and they mention replacing the D11 zener.
http://forum.allaboutcircuits.com/showthread.php?t=39697
Max.

 

I have drawers full of of 400mW glass zeners of hundreds of sizes/types, and every one has at least one paint stripe (or text markings and an anode stripe).

My guess is still a DIAC, which will test as open-circuit on a multimeter diode test but will conduct either direction once voltage is > 32v or so if the O.P. wants to test it further.

 

(or text markings and an anode stripe).

.

I think you meant Cathode?
Max.

 

Doh!

Yes, a stripe on the "stripey" end.

See how confusing it gets when a diode don't have no stripes?