why do old amps has sleeve on the resistors pins... - diyAudio
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Old 31st October 2012, 02:01 PM   #1
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Default why do old amps has sleeve on the resistors pins...

http://i51.tinypic.com/154vldz.jpg
there is a sleeve on the resistors pins what is the reason behind it?
why its not bein used now?
does it makes any difference?
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Old 31st October 2012, 02:25 PM   #2
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Hi rhythmsandy,

Those are ceramic stand-off pillars and are used to help prevent heat being conducted along the resistor leads and into the PCB. They work by maintaining a distance between a hot component and the board while retaining a degree of rigidity and support.
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Last edited by currentflow; 31st October 2012 at 02:29 PM.
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Old 31st October 2012, 02:39 PM   #3
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actually a great idea in any case where there are hot resistors above a PCB...

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Old 31st October 2012, 02:39 PM   #4
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Quote:
Originally Posted by currentflow View Post
Hi rhythmsandy,

Those are ceramic stand-off pillars and are used to help prevent heat being conducted along the resistor leads and into the PCB. They work by maintaining a distance between a hot component and the board while retaining a degree of rigidity and support.
... and give more air to evacuate the heat into the atmosphere.
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Old 31st October 2012, 02:50 PM   #5
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... and give more air to evacuate the heat into the atmosphere.
... and to increase the manufacturing costs!
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Old 31st October 2012, 02:58 PM   #6
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Originally Posted by currentflow View Post
... and to increase the manufacturing costs!
Yeah, but it is other problem.
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Old 31st October 2012, 03:18 PM   #7
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The heat issue is less of a problem with modern PCB materials. The old paxolin type scorch really easily. The downside of standoff is both mechanical (just look at those ceramic coffins on the OP image) and a slight increase in the loop area for inductive pickup.

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Old 31st October 2012, 04:06 PM   #8
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true thanks for the replies guys...
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Old 31st October 2012, 06:48 PM   #9
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I'll take the slight increase in loop area over excess temp in my resistors. If you've got a circuit where that makes any difference, the layout and parts are going to be way different, I would think.

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Old 1st November 2012, 07:13 AM   #10
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Quote:
Originally Posted by currentflow View Post
... and to increase the manufacturing costs!
I believe it is standard practice in (industrial) electronics manufacturing to mount leaded power resistors somewhat above the pcb. One way to do that is to use those ceramic standoff pillars, but that's indeed a more time consuming method.
Another way of doing it is to bend and indent the leads in a specific place such that the leads do not drop through the holes in the pcb all the way. This bending and indenting is done automatically using gear like this, and after setting it up doesn't require much labour.
You end up with components that don't need more time to mount that those without a standoff. The only drawback is that without the ceramic standoff pillars the resistors bend more easily if the pcb is handled carelessly.

Last edited by jitter; 1st November 2012 at 07:16 AM.
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