On 5/15/2012 12:03 PM, klem kedidelhopper wrote:
I'm working on an old Bogen CHS60 60 watt PA amplifier. This is a
direct coupled amplifier and almost every transistor is blown. A real
mess. Except for one small signal transistor,, a 2SA539Y all the
other TO92 types are 2SC945L. In addition there are two TO220 drivers
and two TO3 outputs. I have been replacing the 945 TO92's with 2SC1815
types which is what I have in stock. Both types seem to cross to an
NTE 85 so I figured this would be a safe bet. However I just noticed a
problem. The problem is the two remaining good 2SC945L's on the board
seem to test OK out of circuit however the base is definitely in the
center on both off them. The board is marked EBC for all of these
types as well but the spec sheets for both the 945 and the 1815 types
shows that they are ECB.. The interesting thing here is that the spec
sheet for the 539Y shows EBC as it is marked on the board. I have
never seen where two transistors bearing the same number were
configured differently but is this possible? It certainly seems that I
have installed all these 1815's incorrectly. Does anyone have any
further insight on this? Really confused. Thanks, Lenny
Yes, I have seen that, but was a long time ago. I have owned an
electronic assembly service for over 12 years. Once upon a time we built
something with a discrete commonly available transistor. Suddenly the
product would not work. The problem was traced to a certain transistor
and after a lot of head scratching, we discovered the newly delivered
transistor had a letter suffix after the regular id number.

The suffix meant the ecb configuration was actually a ebc for the same
transistor. Never seen it since and suspect it was a manufacturing error
that was being covered up and being sold to unsuspecting distributors.

Paul