transistor pinout question,..

 

For the SK3007A series and for transistors in general, what does the
tab or colored dot indicate in terms of pinout? The collector?
Sometimes the pinout is diagramed but I don't know if they are showing
the top perspective or the bottom perspective, which would be the
opposite.
Thank you.

 




With rare exceptions devices are shown from the bottom and numbering is
clockwise.









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On 1/6/07 7:52 PM, in article %7_nh.127516$hn.52740@edtnps82, "Homer J


This is a carryover from the days of vacuum tubes. Most early tubes had
larger pins for the heater or filament. That made sure that it took a
determined idiot to plug the tubes into their sockets incorrectly. When
octal and loctal base tubes were put on the market, they had keys that
guided them into their socket in the correct orientation.

The tab on the transistor corresponds to the key on the tube. Numbering was
always as seen from the bottom because that was the direction you looked in
when soldering onto the socket.

Bill
-- Fermez le Bush

 




Yes. IIRC, only some antique Philips tubes were numbered in reverse.












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Going back to the 1960's, Mullard, for one, used a Red dot to signify the
Collector. There was also a lead spacing difference but it was very small and
not easily seen. This dot was used on all round can (both glass and aluminium)
transistors of the OCXXX series. The OCP71 phototransistor used a white line
instead of the dot to signify the sensitive area and most also had the dot as
well.

Once the transistor bodies were moulded it became easy to have a moulded face or
edge to do the same thing.

My stepfather worked at Mullard for 40+ years and I remember going to the New
Road factory in Mitcham for his 25 years dinner in the early 1960's, and being
shown round the valve production lines and then the transistor lines. They made
the OC4X and OC7X series at Mitcham.

All the transistors were tested by hand and sorted by characteristics, piles of
these 'new' things on the benches all being hand sorted by women with
appropriate test equipment.

Peter
--
Peter & Rita Forbes
Email: diesel@easynet.co.uk
Web: http://www.oldengine.org/members/diesel