F5X -- the EUVL Approach - The Build Thread - Page 55 - diyAudio
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Old 15th April 2013, 02:22 PM   #541
EUVL is offline EUVL  Europe
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The load that sees 16.9V 4.1A are not MPC74s, but 4ohm power resistors on heatsink as shown in his photo (gold anodised ones on the RHS).

The MPC74 1R resistors that he mentioned were those for the CRC power supply (white ones on the LHS).
And they are hot to 150 degC at the case, as on our own example of the CRC.
Ambient air next to them are in our own example about 80 degC.
The rest I already explained (why it is OK to have 150degC at the case).

Or anything else that you want to know that I have not answered ?



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Old 16th April 2013, 07:30 AM   #542
AndrewT is offline AndrewT  Scotland
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Euvl,
you are still on a different tack.
I am referring specifically to the test set up,
He tested the PSUs and got odd results.
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Old 16th April 2013, 09:20 AM   #543
EUVL is offline EUVL  Europe
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Design value was +/-16V 4A bias per channel.
Please kindly explain why +/-16.9V (5% deviation) and 4.1A (2.5%) would be an odd result ?


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Last edited by EUVL; 16th April 2013 at 09:28 AM.
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Old 16th April 2013, 10:15 AM   #544
AndrewT is offline AndrewT  Scotland
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Quote:
When testing the +/- voltage of the PS under load, ............... The PS with an 8 ohm load is hovering right at 4A, but I'm not getting very useful +/- voltage readings.
..............
I was confusing myself last night, and was measuring across the wrong points. After giving the PS about 10 min to stabilize, I get +/-16.9V and 4.1A through my 8ohm load resistor. You are right, those Fukushima 1ohm resistor do get hot. I am measuring around 140-145 degrees C in my setup.
I quoted the relevant extracts from Horio's posts.
There is nothing wrong with 16.9V & 4.1A.
But I am questioning his test procedure, in particular the actual resistance used.

This has nothing to do with the quality of your design.

It is about Horio's test results.
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Old 16th April 2013, 10:24 AM   #545
EUVL is offline EUVL  Europe
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> This has nothing to do with the quality of your design.

Good to know.


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Old 16th April 2013, 02:47 PM   #546
Horio is offline Horio  United States
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Andrew, my initial odd results were simply due to my improper measurements. I was simply measuring across the wrong points, and I did not need to change anything with the wiring shown in that photo to obtain useful +/- voltages.

On another note, what sort of ripple voltage (correct term?) should I be seeing when I scope the PS under load? If I have it setup correctly, I'm getting around 150mV peak to peak.

Last edited by Horio; 16th April 2013 at 02:49 PM.
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Old 16th April 2013, 03:16 PM   #547
AndrewT is offline AndrewT  Scotland
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4A draw will create a massive ripple at the first smoothimg.
That's why the CRC or Multiplier or regulator are so important.
Their job is to attenuate that massive ripple to something that when it is applied to the amplifier it becomes inaudible.
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Old 16th April 2013, 04:18 PM   #548
EUVL is offline EUVL  Europe
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> I'm getting around 150mV peak to peak.

About correct, dependent on transformer internal impedance.
Regulator would be much better in that respect.


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Old 16th April 2013, 05:12 PM   #549
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by NicMac View Post
MS22 75004 thermistor and 3.15A slow-blow fuse. All OK.
5 mV ripple P2P (the scope say 100Hz! Why I thought I was living in a 50Hz country).
Rectification and caps does not generate much heat. The R's in the CRC get very warm, but nothing to worry about.
I found much lower ripple, but I will re-check next time I open up the amp.
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Old 17th April 2013, 03:23 PM   #550
lhquam is offline lhquam  United States
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I have not been following all of the details of this thread and the F5X design. What protection circuits (over-current, speaker, ...) if any, are being used or proposed for the F5X? I seem to recall one idea with worked in conjunction with a voltage regulated power supply, but I do not know whether that progressed to fruition.
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