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Post mortem on the body of a resistor

Was it 82K or 100K ? Assuming no other info available other than from the general circuit posistion and other marks of the model , could be either 82K or 100K.

1/2 watt metal oxide resistor, overheated to totally discolour the bands and then open circuit. Scraping an axial line of the laquering off, failure at one end, and the rest measures 100.9K to the point where the MO is blackened and rapidly increases in resistance. Taking readings per turn of the spiral along this axial line, ie sampling, readings are 1.3K,16.8K,40.5K,63.5K, 94.5k. Point to consider , as the R failed at an end rather than at the middle, whether fusible type or manufacturing flaw, it was probably not heated as much as a resistor that failed in the centre, ie normally the hottest point as not heatsinked by the tails and solder etc. I know ,sort of balance of probability-wise , from this data what value I would select as a replacement. But not wishing to bias anyone else's opinion, what would others reading this, opt for 82K or 100K ?
Reply to
N_Cook
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Nigel,

If you'd post the make, model and component location you might find someone here with a schematic and could then know what the original value is.

Regards, Tim Schwartz Bristol Electronics

Reply to
Tim Schwartz

On Mon, 28 Apr 2014 10:27:14 -0400 Tim Schwartz wrote in Message id: :

I think he's referring to Why on earth he started another thread...

Reply to
JW

I've since found the schematic forthat Mark and the original value was probably 91K. I just thought it would be an educative process. I had previously thought , given the choice of 82K and 100K that it would more likely to have been 82K from that set of measurements and no other knowledge. But for the record Fender Concert PR244 of 1994

Reply to
N_Cook

R61 of that not so common schematic of the "Concert" family.

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Agrees with a number of compared component numbers and values Next time I have to do that , reminder to myself, keep one DVM-R probe on the spiral and move the other probe, so alternately down the line, to get a better set of readings. And also repeat a few times , for an average. It looks as though, if 4 loops and same end-failure, then take the reading to use, across the central 2 and double it. The reading nearest the break obviously had increased the most. The intact end reading must have been affected by part of the first loop running along the metal of the end. I would have thought it was the most reliable, least affected. Also to remember as minimum of scraping with razor blade, as any thinning of the MO will increase the readings

Reply to
N_Cook

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