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-   -   Ceramic resistor question. (http://www.diyaudio.com/forums/power-supplies/218771-ceramic-resistor-question.html)

Rod Beauvex 30th August 2012 03:23 AM

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?

sofaspud 30th August 2012 07:22 AM

They can run very hot, yes. Measure the voltage across it and calculate the current; compare that with the nominal designed voltage & current.

Mooly 30th August 2012 07:37 AM

Quote:

Originally Posted by Rod Beauvex (Post 3145114)
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.

AndrewT 30th August 2012 11:53 AM

Ceramic resistors?
Do you mean wire wound inside a protective case?

Rod Beauvex 30th August 2012 01:34 PM

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.

eem2am 31st August 2012 05:17 AM

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)

DF96 31st August 2012 10:36 AM

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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