Re: Silicon transistor failure
Hello,
Interesting thread.
As I don’t commercially repair/restore equipment and the only ‘old’ silicon solid state equipment I see is from Swap meets and the Audio Jumble etc., for my own use, so I can only see it from that perspective.
I suppose we’re possibly facing the terminal aging and the eventual demise of a lot of the 30–50-year-old solid state ‘silicon’ audio gear, as these are littered with TO92 parts. 30–50-years ago the TO92 was the go-to transistor in the first and driver stages of the ‘RCA’ type power amplifier circuit.
Transistor faults in front ends, IF stages and preamplifiers will cause ‘localized’ problems, but in DC coupled amplifiers of 30-100Watts (or more) it’s a different proposition as these higher power DC coupled amplifiers are often to be found in 70’s and 80’s audio equipment, and if multiple small signal transistors in the early and driver stages, go way, way, way off specification, the circuit could catastrophically fall over and fail, and with a domino effect take out the output transistors made from unobtanium and not to mention the speakers if they are DC coupled!
In strange way this thread runs alongside the tread about old radios and “AM closures, less impetus to restore sets?” I suppose if this 70-80’s audio gear starts to fail wholesale on a regular basis, because of multiple transistor failure, it will become uneconomic to fix them, [in a commercial environment], when each fault occurs due to a transistor failure, only to have another transistor fail a week, month or year later.
Maybe the time is approaching where a restoration/recommission will have to include the full careful testing and inspection of ALL the transistors to see if they meet the original basic specification?
The availability of the scarcer power devices is also influencing longevity of these [higher] power amplifiers.
Terry
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