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Old 30th August 2012, 03:23 AM   #1
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Default Ceramic resistor question.

Are ceramic resistors supposed to get extremely hot? I mean to the point of burning you the immediate instant your skin brushes it? I've had two different tube units, both of which had at least one ceramic for voltage dropping, and they both run piping hot. Is this normal, or indicative of other problems?
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Old 30th August 2012, 07:22 AM   #2
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They can run very hot, yes. Measure the voltage across it and calculate the current; compare that with the nominal designed voltage & current.
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Old 30th August 2012, 07:37 AM   #3
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by Rod Beauvex View Post
Are ceramic resistors supposed to get extremely hot? I mean to the point of burning you the immediate instant your skin brushes it? I've had two different tube units, both of which had at least one ceramic for voltage dropping, and they both run piping hot. Is this normal, or indicative of other problems?
Yes it can be normal. Normal to the point that you need high melting point solder to stop them unsoldering themselves.
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Old 30th August 2012, 11:53 AM   #4
AndrewT is offline AndrewT  Scotland
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Ceramic resistors?
Do you mean wire wound inside a protective case?
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Old 30th August 2012, 01:34 PM   #5
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Possibly andrew, yes. Point is, they get hot.

Ultimately, I threw away a tube receiver, albiet a low end one, due to my ignorance on what is normal for how hot these get.
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Old 31st August 2012, 05:17 AM   #6
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Rod, do you mean those white "bathtub" resistors..... the ones that look like a bit of a tile off the side of the space shuttle?..theyre usually rectangle shape.


...if so , yes, in a television company i once worked for....we used to have one in series with a flaback smps...the reason....just in case there was a short across the primary and otherwise the current sense resistors might blow off the board....(health and safety)
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Old 31st August 2012, 10:36 AM   #7
DF96 is offline DF96  England
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Those white ceramic resistors are not very good under severe overload conditions, as they tend to explode. Fine for regular hot use, but if a severe overload is possible then 'health and safety' suggests vitreous enamel encapsulation (often dark green in colour). A TV company ought to know this.
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