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Vishay Dale mil spec metal film resistors

 
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Bruciep07



Joined: 07 Feb 2009
Posts: 248
Location: Central NJ

PostPosted: Sat Feb 06, 2010 9:49 pm    Post subject: Vishay Dale mil spec metal film resistors Reply with quote

I need some info on Dale RN60 resistors... I ordered 1/2 resistors and the supplier I got them from sent me RN60 resistors, which as far as I can tell from the data sheet, are rated at 1/4W. I contacted the supplier and was told that they are mil spec 1/4W which in commercial applications are considered 1/2W. I replied to this supplier that nowhere on the data sheet does it state that they are rated to 1/2W and they assured me that they tested them themselves to 1/2W and they barely got warm. I don't like the idea of using 1/4W resistors in a 1/2W application just because the guy that sold them to me said they were ok... Can anyone confirm any of the info above?
Bruce
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rfgordon



Joined: 02 May 2006
Posts: 658
Location: Virginia

PostPosted: Sat Feb 06, 2010 10:05 pm    Post subject: Reply with quote

The Vishay Dales used in Dumble builds (and are fine in other designs as plate resistors) are the RN65, not RN60.

I've used lots of RN65s, but couldn't comment on the RN60. Compare the data sheets for the two types, and that should tell you what you need to know.

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Jana



Joined: 07 Sep 2008
Posts: 1197
Location: Minnesota

PostPosted: Sat Feb 06, 2010 10:20 pm    Post subject: Reply with quote

I have used lots of RN60's in amps in places that take a 1/2 watt and they are fine. They are physically the size of a regular 1/2 watt. I know, size isn't the whole story, just saying.

Recently I have been using RN65's as my RN60 stock is depleted. No other reason than the 65's were easier to get at the time and the leads were a little longer.

So, bottom line, use the 60's and feel safe.
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C Moore



Joined: 22 Oct 2007
Posts: 1189
Location: USA, California, 94585

PostPosted: Sat Feb 06, 2010 10:44 pm    Post subject: Reply with quote

Is this factual? I mean what Bruciep07 was told by the supplier. Is a "military" watt worth more than a "commercial" watt???
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FYL



Joined: 17 Feb 2006
Posts: 654

PostPosted: Sun Feb 07, 2010 12:07 am    Post subject: Re: Vishay Dale mil spec metal film resistors Reply with quote

Quote:
I contacted the supplier and was told that they are mil spec 1/4W which in commercial applications are considered 1/2W.


The commercial equivalent of the RN60 is the RMF60, rated at .5 watts.

From the RFM datasheet : "(Except for marking, the Industrial and Military versions are exactly the same. Depending upon stock, military marked parts may be supplied as industrial rated parts)".

http://www.vishay.com/docs/31018/cmfind.pdf
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ToneMerc



Joined: 26 Apr 2009
Posts: 2877
Location: East Coast

PostPosted: Sun Feb 07, 2010 12:17 am    Post subject: Reply with quote

hired hand wrote:
Is this factual? I mean what Bruciep07 was told by the supplier. Is a "military" watt worth more than a "commercial" watt???


The supplier is correct.

An "RN" is a military resistor built to a combat specification. It is fit for vibration, humidity, temperature extremes, and operation at maximum rating for long periods of time. For this reason the military power rating is less than the commercial rating. The military specifiction (milspec) for the RN resistor is MIL-R-10509 (M10509 for short).

The RN60 military power rating at 70 degress C is 1/4 watt and 1/8 watt at 125 degrees C. The equivalent commercial power rating at 70 degrees C is 1/2 watt (except .4 watt for Electra).

TM
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Bruciep07



Joined: 07 Feb 2009
Posts: 248
Location: Central NJ

PostPosted: Sun Feb 07, 2010 4:17 am    Post subject: Reply with quote

Thanks for all the replies guys, the data sheet is confusing to me because it shows the equivalent as being the cmf60 and it shows 4 different power ratings in the same column, but being that the watage rating drops down to 1/4W at a specific temp, I just didn't understand how that could still be rated at 1/2W... I think mouser and Newark had them listed as 1/4W... Guess I'll just use them...
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FYL



Joined: 17 Feb 2006
Posts: 654

PostPosted: Sun Feb 07, 2010 12:44 pm    Post subject: Reply with quote

Take a very conservative 40C value for heat rise: 1/2w rating.
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Structo



Joined: 17 Oct 2007
Posts: 14323
Location: Oregon

PostPosted: Sun Feb 07, 2010 5:15 pm    Post subject: Reply with quote

Yeah I remember when I was researching the RN65D resistors.
The way Mouser has them listed I wasn't sure of their rating.

I was looking at the 150K RN65D, the description said it was a 1/2 watt but when I brought the resistor up, it called it a 1/4 watt resistor.

The RN series has a max voltage of 350v, but that is mil spec so more likely you could double that spec.

The power rating is spec'd at .5 watt on the datasheet.

As the voltage rating, you can safely say that this resistor is capable of handling power much above that rating.

The main thing about these resistors is there low noise floor and close tolerances, heat does not affect them like other resistors.

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