F5X -- the EUVL Approach - The Build Thread - Page 43 - diyAudio
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Old 11th February 2013, 07:28 AM   #421
EUVL is offline EUVL  Europe
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> Are the 24pcs of 1k ohm Fukushima resistors for the CRC boards?

24 pcs 1R MPC74, not 1k I hope.
They are for the CRC board.

> We'll be using CRC until the regulator boards are confirmed to be working, correct?

Yes, because the mechanical parts will cost a bit.
Nic will get a set in a couple of weeks, so he will test and then report.
You can then all make up your mind whether to zse CRegC at extra cost, or stay with CRC.

> I have done up my control board and waiting for ashaw to provide instruction on testing.

It appears that there is still a minor bug in the PCB.
We are sorting this out on Nic's 3x protection boards.
Once that is done and proven the solution will be published.
To make life simpler for all of you, please put your protection boards on hold, including soldering.
Bug fixing is easier with an unsoldered board, but Alexis'll also provide a solution for soldered ones.

In the meantime, thank you for your patience.


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Old 11th February 2013, 08:22 AM   #422
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Default Fukushima resistors

This is the one.
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File Type: jpg Fukushima 1R resistors.jpg (521.3 KB, 469 views)
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Old 11th February 2013, 09:01 AM   #423
EUVL is offline EUVL  Europe
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It says MPC74 1R K.
The K stands for +/-10% tolerance (see datasheet).
But we already matched for you.


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Old 12th February 2013, 05:16 PM   #424
Horio is offline Horio  United States
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Question regarding thermal compound. I read through the Linear Audio article on the F5X case/Class A chassis design, and there was a discussion about isolation pads. It sounds like the Keratherm pads do not require thermal compound if the clamping force is high enough (and it may provide better performance this way as well). I'm guessing in our situation, we are not going to be able to achieve a high enough clamping force to justify omitting the compound.

What have you guys done on your builds, and what would you recommend?
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Old 12th February 2013, 05:26 PM   #425
EUVL is offline EUVL  Europe
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No thermal compound required for Keratherm.
It is the whole idea behind such a elastic pad.

If you want to experiment, use a 9V battery and a 10k trimpot to provide a Vgs at any MOSFET.
You may use e.g. a IRFP240. Mount it as if in your normal F5X.
Apply Vgs of say 16V and set the trimpot such that bias is 2A.
Measure both MOSFET case temperature and heatsink temperature immediately next to the FET.
You should find that the difference is between 2~4C.
Then you are doing just fine.

One or two degrees difference is not going to kill your FET.
The thermal resistance between substrate and case varies a lot more.


Patrick
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Old 13th February 2013, 09:35 AM   #426
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Patrick

I can use IRFP240 9240 as output devices Instead of Toshiba with F5X without problems ?
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Old 19th February 2013, 07:49 PM   #427
NicMac is offline NicMac  Italy
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I'm ready to stop testing and start listening, so before I close it up for a few weeks here are a few pictures of my build.
Everything is perfectly functional with the exception of the output protection circuit where there still are a few bugs to fix (at least in my builds). Power and relay control works so it is functional enough to be used.
Attached Images
File Type: jpg IMG_0869.jpg (114.4 KB, 322 views)
File Type: jpg IMG_0870.jpg (47.2 KB, 318 views)
File Type: jpg IMG_0871.jpg (36.3 KB, 271 views)
File Type: jpg IMG_0872.jpg (90.0 KB, 285 views)
File Type: jpg IMG_0873.jpg (77.6 KB, 225 views)
File Type: jpg IMG_0874.jpg (94.6 KB, 216 views)
File Type: jpg IMG_0875.jpg (71.6 KB, 216 views)
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Old 19th February 2013, 09:56 PM   #428
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Looks fantastic. Kudos to all involved.
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Old 19th February 2013, 10:01 PM   #429
JBdV is offline JBdV  Netherlands
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Great job Nic!!!

Did I notice my stickers on some of your FETS (not sure..)
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Old 19th February 2013, 10:28 PM   #430
NicMac is offline NicMac  Italy
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I am about to "dock" the transformer cradle, but there is one thing that does not convince me.......

The cradle is fixed to the chassis by screws from the top side. However there is no way of tightening (or even insert) these screws when the back-panel has been wired up - and absolutely no way when the cradle is in.
A tiny construction flaw

Unless Patrick stops me with a better idea, I will glue in bolts on the chassis (in)side, drill out the cradle, and fix with washer and nuts from the button.....
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