Since the pinout of the device seems to be in question, I will offer the
following tip:
Identification of the Base pin is not a problem as it will show ordinary
diode conductivity to both the Collector and Emitter. Forward conductivity
for NPN devices, reverse for PNP.
Now to distinguish the Collector from the Emitter, I have found in _all_
cases that the Base to Collector junction will show higher conductivity
(lower drop) than the Base to Emitter junction.
This can be checked with a simple ohmmeter with a decent low ohms scale -
The BC junction will register lower ohms that the BE junction.
However, and even better - Most modern digital VOMs have a "Diode Test"
function which emitts a constant current of 1 to 2 ma and displays the
voltage drop across the junction. Using the "Diode Test" function the BC
junction will show a lower voltage drop that the BE junction.
This effect is more pronounced for power devices, but is clearly
demonstratable on even all small signal devices that I have tested.
btw, the device under discussion here sounds very much like an ordinary
2N3904.
These "commodity grade" bipolar devices had very wide specification limits
for beta and finding them with "beta grading" by color dots was common
practice in my experience.
Best wishes, Bob Smith
--- Avoid computer viruses, Practice safe hex ---
-- Specializing in small, cost effective
embedded control systems --
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Robert L. (Bob) Smith
Smith Machine Works, Inc.
9900 Lumlay Road
Richmond, VA 23236 804/745-2608
[EMAIL PROTECTED]
----- Original Message -----
To: "Multiple recipients of list CHIPDIR-L" <[EMAIL PROTECTED]>
Sent: Thursday, July 01, 2004 7:28 PM
> > Hi Jens,
> >
> > I know this is not a chip-related question, but it's semiconductors, so
> > it's at least half on-topic.
> >
> > I'm repairing my Hameg HM604 oscilloscope, it's not switching off the
beam
> > on backtrace and during wait-for-trigger. I checked transistors in the
> > intensity control area (I have no schematics), and found one transistor
> > with funny behaviour - I can measure three diodes, so I'm pretty sure
this
> > one is in silicon Nirwana.
>
> I have the HM605 with schematic. Perhaps there is some similarity.
>
> As for the BF311, now your received 2 different pinouts: Declan's and
> Pieter's. Pieter's pinout is the same as in my databook. But in my
> databook the oblique edge is on top instead of on side as at your
> image.
>
> In the schematic of the 605 the fly back suppresionpuls is coupled to
> the cathode circuit of the CRT, which is at high negative voltage, by
> an opto coupler. The output of the opto coupler is amplified by a
> complementary pair (BF440 (PNP) and BF199 (NPN)) and given to the
> cathode.
>
> I will not be difficult to find a replacement to this transistor. The
> typical transition frequency is 750 MHz. The max voltages are rather
> low.
>
> Gr�sze, Harry
> >
> > The question I have is about the pinuot of this type, and how they
marked
> > the parts back then:
> >
> > http://think42.com/bf311.jpg
> >
> > Both these transistors come out of the oscilloscope. The right one
behaves
> > correctly, assuming that the base is the right pin (I can measure two
> > diodes to that pin, and the other two have no connection in either
> > direction, which is correct for TO92Z package). The left one has diodes
> > between all pins (not shorts!), so I assume it's dead. The question is:
Why
> > has the TFK one (left on the picture) blue paint on top? Why did Hameg
use
> > different manufacturers for same-type transistors? There is no other
> > transistor with blue marking on top, and it did not look like this one
has
> > been exchanged before (except someone did a *very* clean repair job). Is
it
> > some marking to distinguish between TO92 (CBE pinout) and TO92Z (ECB
pinout)??
> >
> > I did not find any reliable data using Google, only some places that say
> > this type is obsolete. Any help in finding the right replacement is
> > appreciated.
> >
> > ciao,
> > --
> > Jens Sch�nfeld
> >
> > --
> > Author: Jens =?iso-8859-1?Q?Sch=F6nfeld?=
> > INET: [EMAIL PROTECTED]
> >
> > Fat City Hosting, San Diego, California -- http://www.fatcity.com
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>
>
> --
> Author: H.C. Croon
> INET: [EMAIL PROTECTED]
>
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Author: Bob Smith
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