F5X -- the EUVL Approach - The Build Thread

[EUVL]

> 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.


Patrick

[pmchoong]

This is the one.

[EUVL]

It says MPC74 1R K.
The K stands for +/-10% tolerance (see datasheet).
But we already matched for you.


Patrick

[Horio]

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?

[EUVL]

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 2~4°C.
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

[samoloko]

Patrick

I can use IRFP240 9240 as output devices Instead of Toshiba with F5X without problems ?

[NicMac]

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.

[buzzforb]

Looks fantastic. Kudos to all involved.

[JBdV]

Great job Nic!!!

Did I notice my stickers on some of your FETS (not sure..)

[NicMac]

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.....