A guide to building the Pass F4 amplifier

This link may also be a help as a reference, be aware that it doesn't look to be to scale...

I'm wondering what the lead spacings for the 220uF caps on the F4 board are...

Appears to have two solder pad choices for either roughly 5 or 7 mm

Those are the files I was trying to get to scale. I may just take the heatsinks with the file to a machine shop and let them do the math. Would save a chunk of change to have one.

As far as the pads go, I'm going to make an assumption the ones from the store are adequate...
http://www.diyaudio.com/store/parts/keratherm-red.html

but being that I need 24 of them it is going to add up... $60 for insulating pads...
 
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Hi all

A question about the Keratherm / kerafol heat conductive foils for T0247 which exist in several versions :

* the 86/82 Rot as sold by DA Store (2$/pce), difficult to find in Europe
- thermal resistance 0.09 K/W
- thermal conductivity 6.5 W/mK
- http://www.kerafol.com/fileadmin/us...gement/produkte/86_82/Datenblatt_86_82_EN.pdf

* the 70/50 Braun as sold by Conrad is much cheaper (0.4$/pce) Feuille thermoconductrice 70/50 TO 247 0,25mm Kerafol KERATHERM BRAUN 70/50 sur le site Internet Conrad | 180346
- thermal resistance 0.44 K/W
- thermal conductivity 1.4 W/mK
- http://www.kerafol.com/fileadmin/us...gement/produkte/70_50/Datenblatt_70_50_EN.pdf

So, is the 70/50 good enough for F4 application (I have 3 to build so would be glad to save 60$ on that parts) ? Is there alternatives ?

Kind regards
Jean-Louis

Hi Jean-Louis,

I bought sheets from Conrad and just cut the size I need. They are available from Conrad in sizes 100x100mm and 190x190mm:

Feuille thermoconductrice 86/82 rouge 100X100X0,25 mm Kerafol KERATHERM ROT 86/82 sur le site Internet Conrad | 189056

Feuille thermoconductrice 86/82 rouge 190X190X0,25 mm Kerafol KERATHERM ROT 86/82 sur le site Internet Conrad | 189058

Works out a lot cheaper :)

Good luck,

Albert
 
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I used Laird A15038003, Mouser carries them for .28 each.
They worked great for my F4, i only have a 5C difference from middle pin to the heatsink next to the TO-247 package.
They are silicone coated polyamide film.

My F4 is at double the specified bias.
 
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I'm going to try those Laird pieces as well.

Is 7.5mm lead spacing OK for the F4 boards 220uF caps?

In my notes I was landing on the Antek AS-4218 but it seems unavailable at this time. (AS-4218 - 400VA 18V Transformer - AnTek Products Corp) Even eBay came up dry.

I guess I can go with the AS-5218 (AN-5218 - 500VA 18V Transformer - AnTek Products Corp) but maybe that's overkill... What are some other good options? Thanks

I'd also like to share a heat sink option which looks like it will fit for the diodes of the V3 PSU boards, the item listed in the BOM is currently unavailable at Mouser. (http://ca.mouser.com/Search/ProductDetail.aspx?R=EA-T220-51E)
 
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I'm going to try those Laird pieces as well.

Is 7.5mm lead spacing OK for the F4 boards 220uF caps?

In my notes I was landing on the Antek AS-4218 but it seems unavailable at this time. (AS-4218 - 400VA 18V Transformer - AnTek Products Corp) Even eBay came up dry.

I think 7.5mm lead spacing will work. I ordered caps with 5mm leads. Just took them out of the bag and held up against the board. It appears the board was designed for the option of the smaller size like I have or a larger size which is about 2mm larger lead spacing, and roughly twice the diameter in cap size. There is a second set of pads for what is probably 7.5mm. I tried to measure, but couldn't find my glasses and calipers at the same time

I was advised to purchase the Antek 400VA 20V option... I don't know if it ever gets stepped down or just operates at a slightly higher voltage.
 
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I used the AS4218 from antek.
There are other options from Hammond and Triad but nowhere near the price.
I was originally going to use the AS3218 from Antek, if you aren't planning on cranking the bias like I did then it will be more than enough.

You could probably use the AS4220 and burn a volt or 2 in the CRC.
 
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The 5U chassis from the store...
Does it have enough heatsink to dissipate FOUR F4 boards? I could see how heat may rise so the boards on top would be warmer than those on the bottom.

It doesn't have mounting holes for the third and fourth boards but drilling and tapping 8 holes is much easier than the other option which would be tapping at least ... 60 - 80, a minimum of 40 of them would be blind holes which are much more difficult.

I could build a PSU chassis for $40, if a pretty faceplate isn't required. Not sure how much heat dissipation is needed. So far plan is to use the monolithic bridge rectifiers.

The cost of heatsink for my project is $400 minimum, and some options which would work are very close to the size of the 5U heatsinks.
For each board, 300mm x 110mm x 50mm is the smallest I was considering but 300mm x 145mm x 50mm is what I would prefer. 10mm base on the heatsinks, with 40mm fins.
 
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No, I would notice the fans failing.
They are open frame so you see them spinning right in front of you.
Usually when PC Fans fail they won't initially spin up.
With modern Fluid Dynamic bearings they will run for many years without issue.
 

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I'm going to try those Laird pieces as well.

Is 7.5mm lead spacing OK for the F4 boards 220uF caps?

In my notes I was landing on the Antek AS-4218 but it seems unavailable at this time. (AS-4218 - 400VA 18V Transformer - AnTek Products Corp) Even eBay came up dry.

I guess I can go with the AS-5218 (AN-5218 - 500VA 18V Transformer - AnTek Products Corp) but maybe that's overkill... What are some other good options? Thanks

I'd also like to share a heat sink option which looks like it will fit for the diodes of the V3 PSU boards, the item listed in the BOM is currently unavailable at Mouser. (EA-T220-51E Ohmite | Mouser)

7.5mm spacing should be fine, though the recommended Elna caps are in stock.

I used the AS-5218 in my build as the 400va was out of stock. Only issue i ran into was lack of physical space for the toroid and psu board with rectifiers inside the 4U case, hence i had to stack them.

Heatsinks i used, also cheaper :p 531202B02500G Aavid Thermalloy | Mouser
 
The cost of heatsink for my project is $400 minimum, and some options which would work are very close to the size of the 5U heatsinks.
For each board, 300mm x 110mm x 50mm is the smallest I was considering but 300mm x 145mm x 50mm is what I would prefer. 10mm base on the heatsinks, with 40mm fins.

Do not scrimp on heatsinking. I did on an F5T build and dearly paid for it by blowing up all the output devices.