[HomeBrew] Need some help!

[Ian Wilson]

Looking at the NTE equivalents page (www.nteinc.com):

The SK550 (NTE5260) is an 18v, 5%, 50W part.

It is also available in a "reverse polarity" configuration (NTE5260AK).

The standard part has Anode to case; the reverse part has Cathode to
case.

Hope this helps,

de ian, k3imw/6


> 
> I have a SK550 (918) zener diode that I believe to be  rated at  12VDC
@
> 50W.  There appears to be ( barely visible) an arrow pointing away
from
> the metal threaded housing towards the cathode end.  When tested with
the
> VOM on the diode scale, it conducts (value of 770)  with the  negative
> (black)  lead on the metal base and the positive lead on the insulated
> end.  No meter  indication when the leads are reversed. So far so
good!
> What concerns me is that I checked it with another Western Electric
> zener diode clearly identified with numbers and symbols  and the
> positions of the two VOM leads must be reversed in order to get it to
> show a value. In this test, the red lead (+)  is on the base and the
> negative  lead  is on the output end ( direction of arrow ) . This
> particular 50w zener was working fine on a two hole 8877 I built some
> time ago;however, I pulled the zener to do some extensive bias
rewiring
> and cannot recall how it was originally wired. The question is
basically
> which orientation should I use. Follow the arrow or reverse the diode
and
> follow the wiring scheme dictated by the VOM . Is there anyone
familiar
> with the SK550 in order to:
> 	A. verify its identification?
> 
> 	b.  help get the orientation correct?
> 
> 	For obvious reasons,  I'd rather not use the cut and try
approach. Any
> help would be appreciated. Dealing with lots of power so I want to
ensure
> I get it right the first time. Ron W2CQM/3
>