Grinding away a resistor?

Thread Starter

retched

Joined Dec 5, 2009
5,207
What would be the reason for this:
[ed]
updated photo for clairity

[/ed]

It is the best shot I could get, sorry about the blur..why would you grind away a resistor? is it because the manufacture bought the wrong resistors and edited these to make them work?

It looks bad in the photo, but it is "perfectly" ground. Not "blown". no traces of heat or damage other than intentional.
 

Attachments

Last edited:

beenthere

Joined Apr 20, 2004
15,819
That looks like a way to make a high resistance out of a low value resistor. And you actually can cut a notch into a 2 watt carbon resistor to produce a higher resistance. As the notch gets deeper, the resistance goes up while the conductive path gets smaller.

That says that employee time is worth less than carbon resistors, though.
 

Thread Starter

retched

Joined Dec 5, 2009
5,207
That was my thought. We have 100 ohm resistors, we need 500 ohm... here Jimmy, grab a file and a meter and make these into 500 ohm resistors. I'll give you a glass of water and a dollar a week.
 

Thread Starter

retched

Joined Dec 5, 2009
5,207
I think i could understand it more for high accuracy test equiptment. But, without any protection from burning a house down? This is straight from the mains. about a half millimeter from the wiper on the POT.
 

hgmjr

Joined Jan 28, 2005
9,027
If this has to be done then there is one precaution I believe should be exercised. Once you open up these gapping wounds in the resistor, I would expect that some provision would need to be made to reinstate the breached protection against the absorbsion of moisture with its inevitable impact on the components resistance. Perhaps something like clear enamel paint would need to be applied to the resistor to re-seal it.

hgmjr
 

davebee

Joined Oct 22, 2008
540
A friend's car once had a piston pin retainer break, and the piston pin worked its way sideways until it started to rub on the cylinder wall, and proceeded to mill a beautifully neat, clean slot into the cylinder wall. It was so neatly done that my friend thought at first that it was meant to be there for some reason, porting gasses or something.

My point is that maybe a mechanical accident could have cause this? Could a rotating shaft have rubbed on the resister? It sounds not very likely but you never know...

Speaking of slotted capacitors, I've seen ceramic caps with neatly cut slots where the slots contain built-in spark gaps for overvoltage protection (this was from an old television set high-voltage circuit). Maybe that was the purpose of the Fluke caps?
 

spinnaker

Joined Oct 29, 2009
7,830
That was my thought. We have 100 ohm resistors, we need 500 ohm... here Jimmy, grab a file and a meter and make these into 500 ohm resistors. I'll give you a glass of water and a dollar a week.
And I will give you a $100 if you can find someone working in a Chinese factory with the name of "Jimmy". :)


BTW Does your camera have a macro setting? Also helps if you but more light on the subject.
 

Thread Starter

retched

Joined Dec 5, 2009
5,207
BTW Does your camera have a macro setting? Also helps if you but more light on the subject.
I am actually a pretty proficient photographer.. Worked for a few years selling cameras and teaching photography. But this was a cell phone camera. No such options.

I will use my camera and repost for interest.
[ed]

[/ed]
 

Attachments

Last edited:

spinnaker

Joined Oct 29, 2009
7,830
Now that is a photo!


Yeah those cell phone cameras stink. :)

Loots like they ground the PCB too. Probably had a bunch of boards built up then they realized there was a design problem or a board stiffing problem. Must have been easier for "Jimmy" to grind them away then replace them.
 

Thread Starter

retched

Joined Dec 5, 2009
5,207
Poor, poor Jimmy. I can see the guy (or girl) sitting at a scope with a huge box of these things on the left, a dremel in their hand and a box for the "fixed" ones on the right. On the wall there is a sign that says: "You live for the good of the Company"
 

KMoffett

Joined Dec 19, 2007
2,918
"here Jimmy, grab a file and a meter and make these into 500 ohm resistors."
Definitely cheaper and takes up less space than a trim pot. ;)

ken
 

bertus

Joined Apr 5, 2008
22,270
Hello,

By grinding the resistor its value must be gone up as the carbon bar (the black part) is getting thinner.
A bit stange method.

Greetings,
Bertus
 

Wendy

Joined Mar 24, 2008
23,415
But effective, if only for the short term. Notice the type of resistor? Those old suckers drifted badly before they were modified, though modified doesn't seem strong enough. With the seal broken and the material exposed to air I suspect they walk all over the place, mostly increasing in value over time.

I'm not sure of this, but it would seem the wattage would also decrease.
 

Thread Starter

retched

Joined Dec 5, 2009
5,207
mostly increasing in value over time.
Dang, then this sucker should be worth fifty bucks!:eek:

;) -- kidding --

there seems to be a good amount of interest in this resistor.

Shall I pull it so I can read the value stripes then meter it to see what they got?

I suppose I could O'scope it over a range and see how she holds.

If no one cares, ill skip it.
 

Wendy

Joined Mar 24, 2008
23,415
I think the amount of interest is proportional to the amount of disbelief someone would do this. Kind of a techie nerds version of
"Believe it or Not!".
 
Top