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Old 15th September 2006, 02:18 AM   #1
jarthel is offline jarthel  Australia
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Default layout help

I have 3 ASC polypro in metal cans. 1 is a cap filter. and the other 2 are coupling cap.

Since space is limited on the top of the chassis, I am thinking on mounting them 1cm apart. the fitler cap would be around 1.5cm to 2cm away from the PSU choke.

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I also have 4 tubes which would be part of the power supply (tube regulation as found in rdh 14 chap 33).
  • The 5u4g would be around 2cm away from the power transformer chassis.
  • The 6AS7G would be 2cm away from the 5u4G.
  • The 6sl7 and 5651 would form a triangle together with the 6AS7G and would be around 2cm away from the 6AS7G.

The measurements are not for the base but for the glass enveloped since the 5U4G and 6AS7G are ST shaped.
==================

The ASC caps would be around 5 to 6cm away from the glass envelop of the 5U4G and 6AS7G.

Thank you for the help.
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Old 15th September 2006, 05:37 AM   #2
poobah is offline poobah  United States
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You know... I have seen tube data sheets that listed values for spacing. I looked around a bit... of course, I couldn't find diddly.

2 cm gap seems a wee bit small especially for those monster STs. Could you open it up a bit? Say like 3 cm? Tubes lose their heat in all three ways; some conduction, mostly convection and radiation. A little more distance would help on the last 2.

I did find this link though...

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Old 15th September 2006, 05:57 AM   #3
jarthel is offline jarthel  Australia
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from you're reply I'm getting the impression that I do not have to worry about the caps even if they are 1mm away from each other?

thank you.
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Old 15th September 2006, 06:58 AM   #4
CLS is offline CLS  Taiwan
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In Morgan Jones book, it's mentioned dealing such issue with adjusting the orientation of plates to proper directions. Turning the biggest area facing empty space (or which can sustain the heat).

So the heat radiations from big tubes can minimize their interferences & effects on other component (like caps).
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Old 15th September 2006, 08:37 AM   #5
jarthel is offline jarthel  Australia
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Quote:
Originally posted by CLS
In Morgan Jones book, it's mentioned dealing such issue with adjusting the orientation of plates to proper directions. Turning the biggest area facing empty space (or which can sustain the heat).

could you explain "turning the biggest area"?

My impression is that you meant:

the plates must be perpendicular to the caps so that only a small portion of the plate is facing the caps. is this correct?

thank you
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Old 15th September 2006, 08:44 AM   #6
CLS is offline CLS  Taiwan
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Yes. Correct.

This also applies to those side by side big power tubes. When 2 power tubes are close to each other, it'd better turning the smallest plate area to face each other. Or they will "bake" each other face to face.
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Old 15th September 2006, 08:47 AM   #7
jarthel is offline jarthel  Australia
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Quote:
Originally posted by CLS
Yes. Correct.

This also applies to those side by side big power tubes. When 2 power tubes are close to each other, it'd better turning the smallest plate area to face each other. Or they will "bake" each other face to face.

thanks for the tip.

anyone else?
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Old 15th September 2006, 12:23 PM   #8
Sherman is offline Sherman  United States
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I have built power supplies with ACS run caps as filters. I have put them very physically close to each other and to the choke (but they were well away from the PTX). The amps were dead quiet, no hum even with my ear inches from the speaker.

I would guess I had 2 cm between the first cap and the choke, and about 1 cm between caps.

I didn't use the ASC caps as coupling caps so I can't comment on that part of your layout.
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Old 15th September 2006, 02:36 PM   #9
poobah is offline poobah  United States
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Jarthel,

As far as the caps are concerned... yes, they can be mounted very close as they won't be producing much heat.

You did mention some coupling caps... these should be placed as near as possible, between that is, the circuits they are coupling.

Start with a schematic last has a clean layout, then your physical layout should mirror in some way your schematic... This will lead to each conductor being as short as possible. Don't fall into a "big things on this side" mentality.

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Old 15th September 2006, 05:26 PM   #10
Sherman is offline Sherman  United States
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Quote:
Originally posted by poobah
... Don't fall into a "big things on this side" mentality.

Great advice Poobah. Though I have to admit it took me a while to be able to "see" the physical layout from a schematic. Sometimes with more complex things I still struggle to optimize but a nice clean schematic is the best place to start.

A related note- One mentality worth falling into (most of the time) is "noisy things on this side". Though often that "rule" can be bent quite a bit before bad things happen.
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