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agardiner · 29th Mar 2023, 9:37 am

Has anyone noticed transistor failure becoming more common? It may be coincidence of course, but I have had quite a lot of repairs lately, dating mainly from the late 70's through to the late 80's, where multiple transistors had failed in the unit. Of note is the failure mode; they appear to all have gone low gain.

Testing such transistors with a multimeter is useless, as they test perfectly fine. However, a proper tester shows low Hfe and in circuit they just don't work. This is primarily in RF and IF positions on course, so junction capacitance may be playing a part as well, but I have also found problems in audio sections where they are still functioning, but the amp is low gain until the offending component is replaced.

Has anyone else noticed this? I do think it is the age that some of these are now, and suspect it may become more common. Oh, and I am referring to TO92 silicon transistors, not the dreaded lockfit types!

29th Mar 2023, 9:37 am	#1
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,741	Silicon transistor failure Has anyone noticed transistor failure becoming more common? It may be coincidence of course, but I have had quite a lot of repairs lately, dating mainly from the late 70's through to the late 80's, where multiple transistors had failed in the unit. Of note is the failure mode; they appear to all have gone low gain. Testing such transistors with a multimeter is useless, as they test perfectly fine. However, a proper tester shows low Hfe and in circuit they just don't work. This is primarily in RF and IF positions on course, so junction capacitance may be playing a part as well, but I have also found problems in audio sections where they are still functioning, but the amp is low gain until the offending component is replaced. Has anyone else noticed this? I do think it is the age that some of these are now, and suspect it may become more common. Oh, and I am referring to TO92 silicon transistors, not the dreaded lockfit types!