Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Apexelectric on August 20, 2022, 11:56:30 am
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Was wondering if anyone knew anything about these resistors?
I got a bag full in three sizes and various values of each. They are about the size of typical 1/2W, 1W, and 3W metal oxide resistors. They also have what appears to be vent holes on both ends that lead me to believe that they are metal encapsulated power resistors?
Just curious to know a little more about them before I decide where to use them.
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It looks like a metal oxide type to me. Probably a ceramic body...usually solid in modern construction. The brass-looking end caps with radial hole pattern are probably crimped on before the paint/marking is applied.
The holes suggest an airflow function, but I'm guessing...there is not likely a path thru the resistor like tubular wirewounds from the old days. So the holes may not serve any purpose for cooler air from the outside but might serve some function to relieve physical stress in the resistor over the range of temperature it may experience between cold, unpowered and hot at full power.
Or to control how the component fails under worst case...something the resistorologists realized makes a less explosive failure.
Weakly analogous to various pressure-relief physical features we see in electrolytic capacitors. The end (top, bottom, or both depending on design) can get forced off less violently than a loud explosion that sprays particles throughout the device it's installed end.
Not everyone appreciates fireworks indoors ;@).
Or I have a very creative imagination and can shovel verbal manure faster than the average bull can deliver it.
OK, I just deleted a paragraph about breaking ceramic components for curiosity's sake. Not always a good idea, more risk than information to gain
Murray
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It looks like a metal oxide type to me. Probably a ceramic body...usually solid in modern construction. The brass-looking end caps with radial hole pattern are probably crimped on before the paint/marking is applied.
The holes suggest an airflow function, but I'm guessing...there is not likely a path thru the resistor like tubular wirewounds from the old days. So the holes may not serve any purpose for cooler air from the outside but might serve some function to relieve physical stress in the resistor over the range of temperature it may experience between cold, unpowered and hot at full power.
Or to control how the component fails under worst case...something the resistorologists realized makes a less explosive failure.
Weakly analogous to various pressure-relief physical features we see in electrolytic capacitors. The end (top, bottom, or both depending on design) can get forced off less violently than a loud explosion that sprays particles throughout the device it's installed end.
Not everyone appreciates fireworks indoors ;@).
Or I have a very creative imagination and can shovel verbal manure faster than the average bull can deliver it.
OK, I just deleted a paragraph about breaking ceramic components for curiosity's sake. Not always a good idea, more risk than information to gain
Murray
I’d be happy to sacrifice one or two for the sake of identifying exactly what these are. For what it’s worth, the vents pass through the entire length of the resistor. Mostly curious about who the manufacturer was and if they are more modern or vintage or if they are fairly common or more rare and sought after.
Thanks for the input
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Measure the resistance of the one in the pic. orn-orn-red-red.
I'm asking because I don't think it is a resistor. I think it's a 3300µH inductor.
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Measure the resistance of the one in the pic. orn-orn-red-red.
I'm asking because I don't think it is a resistor. I think it's a 3300µH inductor.
I checked a few. They’re definitely resistors
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i'm in for metal oxide, flame-proof Resistor.
very common, guessing around year 2000. that's about the time the distinct paint "colors" became not so distinct.
red, orange n brown is not the same in USA as CCP :icon_biggrin:
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I have some FP resistors that look kinda like that. (Or maybe slightly different? I‘ll dig them out to confirm)
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I sacrificed one to see what was going on inside and what I found was the body looks like clear glass. There are two metal end caps and the whole thing is coated in a metal oxide. The holes in the end caps can’t be vents since the internal structure is solid. I thought it was a vent since I could see daylight through it from one end to the other but it was because the body was clear, like glass.
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After searching for “glass resistor” it appears these were made by Corning and date from a while ago. Don’t seem like they’re anything too special but will have to investigate more as to what they might be good for.
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what they might be good for.
anything a "normal" resistor is good for :laugh:
if i recall, those holes are for gas to escape when things go catastrophic
I remember having a SS amp on the bench when a 1/2W failed, the center turned glo-red, smoke could be seen exiting the sides, a small "crack sound" took ~~ 1second. The transistor it was protecting was shorted.
i swapped everything connected to the transistor and moved on to the next thing wrong
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what they might be good for.
anything a "normal" resistor is good for :laugh:
if i recall, those holes are for gas to escape when things go catastrophic
I remember having a SS amp on the bench when a 1/2W failed, the center turned glo-red, smoke could be seen exiting the sides, a small "crack sound" took ~~ 1second. The transistor it was protecting was shorted.
i swapped everything connected to the transistor and moved on to the next thing wrong
Ha, yeah, I guess I had that coming.
Just wasn’t sure if these had any special qualities to them that would lend itself to being better in a specific application or if they’re just a plain old resistor with a glass former. Seems like the latter.