On 29/06/2020 12:24 pm, Phil Allison wrote:
Trevor Wilson wrote:

================


**If I have a weird fault, I always suspect high value (100k) or low
value (100 Ohms) resistors.

** That is why I went on a bad resistor hunt - after everything else proved OK.

**The most painful ones I've seen were popular in Sansui products a few
decades back. They were typically in the range of 100 ohms ~ 47k and
would go high. Frequently to around double the value printed on them.
Fault finding was very difficult, since Voltages were almost what they
were supposed to be. Almost, but not quite.



That said, mostly I find such faults confined to cracked carbon resistors.


** Small carbon film resistors regularly fail (open) due to high voltage "tracking" between turns on the spiral cut. Plate resistors in triode stages for one.

IME - metal film and cermet types ( ie chip resistors) are less prone to do the same.

**I've seen plenty of 100k resistors go high, despite being subject o
Voltages of less than 40 Volts.


--
Trevor Wilson
www.rageaudio.com.au

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