Jens Sch�nfeld wrote:
Hi list,
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.
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)??
Jens, you are asking me to recall some pretty old brain cells. Color marking was used for a number of functions. As I recall these transistors were sold with a very wide beta range (~100-~500). The colors defined various beta sub-ranges. In the factory we used to select for breakdown voltage, beta match, and noise figure.
As far as why they would use two manufactures. It was always nice to have at least two manufactures for every part (I think this is a requirement for jedec registry). It you wanted to control which manufacture was used you had to assign two part numbers. Since most MRP systems couldn't handle two part numbers for one stuffing location it was seldom down.
As for testing it is usually easier to test in circuit rather than using an Ohm meter. Vbe should be a pretty constant 0.6v when turned on (saturated). Vce should be a few tens of a volt when turned on. Open 'be' and shorted 'ce' junctions where the most common failure modes.
Fred Townsend
I did not find any reliable data using Google, only some places that say this type is obsolete.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,
-- Author: Fred Townsend INET: [EMAIL PROTECTED]
Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
