F5X -- the EUVL Approach - The Build Thread - Page 60 - diyAudio
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Old 20th May 2013, 04:52 AM   #591
EUVL is offline EUVL  Europe
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> Before CRC = 21,4V

That is OK.

> After CRC = 19,8V

Difference before and after CRC is 1.6V.
R in the CRC is 0.67R.
So your total bias per balanced F5X is at this moment 2.4A.
Dissipation per FET is 24W per FET, so nothing detrimental will happen.

For optimum output at 6 ohm load, total bias current per channel should be 4A when fully warmed up.
Suggest you check voltage across the 0R22 resistors on the F5X PCB.
To be on the safe side you can start with cold bias (room temperature) of 1.5A.
That means voltage across the 0R22's should be all 0.33V at start up.

And please read Dave's excellent instructions at the start of the thread.


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Old 20th May 2013, 04:41 PM   #592
ramallo is offline ramallo  Europe
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Can I get the rectifier pcbs?, my pcb without plated-through holes is very problematic
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Old 20th May 2013, 04:55 PM   #593
EUVL is offline EUVL  Europe
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They were already offered in January ?
F5X -- the EUVL Approach - The Build Thread

If you still want some now, you can contact WK.
But we need to add service charge for the extra time and cost to go to the Post Office just for you.
Unless you can wait till the regulator GB is finalised.


Sorry for that,
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Old 1st June 2013, 02:15 PM   #594
Horio is offline Horio  United States
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I'm getting the hang of soldering tiny SMD parts. Not so bad when you have good liquid flux and some good braid!

For the red LED's on the protection board (D5_L, D5_R, D6_L, D6_R), how do I know which way the polarity is on the soldermask? Is the tapered end the negative (cathode) end? So the green marking on the underside of the diode should point toward the end with the taper (or right side when reading the soldermask label)?

Click the image to open in full size.
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Old 1st June 2013, 02:49 PM   #595
NicMac is offline NicMac  Italy
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I had the same doubt. Fact is that it does not matter as the two LEDs are antiparralel in the circuit. So just place them in opposite relative orientation
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Old 1st June 2013, 03:56 PM   #596
Horio is offline Horio  United States
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Thanks Nic!

I also noticed a couple of discrepancies in the BOM of the Protection Board F5X Chapter 1 article.

1. R33L/R and R34L/R call for a 120ohm resistor under the "description" column but indicate a 300ohm resistor under the "comment" column which is what Alexis provided with his GB. What is the correct value to use here?

2. R32L/R call for a 2.0 kohm resistor under the "description" column but indicate a 2.7 kohm resistor under the "comment" column which is what Alexis provided with his GB. What is the correct value to use here?

Thanks!
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Old 1st June 2013, 05:19 PM   #597
EUVL is offline EUVL  Europe
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Those values were revised and the reason of revision is already explained in the document.
Please read it through. The new values are valid.

For the polarity of the SMD LEDs, just go to Digikey and dig out the data sheet.
This is what I do every time before I solder those things, unless I already have it on my laptop.


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Old 1st June 2013, 07:03 PM   #598
NicMac is offline NicMac  Italy
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The markings on the LEDs are easily located/understood (even if they can only be seen before the LED is mounted). To me it was the non standard (to me at least) markings on the PCB that were not easily understood.
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Old 1st June 2013, 07:43 PM   #599
ashaw is offline ashaw  Australia
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Cathode is allways pin 1, pin one is always the end with an identifying mark, I.E. the curved end.

This was just pulled out of a standard footprint library, if I were to redesign this today I would have designed my own that is more unambiguous.
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Old 1st June 2013, 09:08 PM   #600
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by ashaw View Post
Cathode is allways pin 1, pin one is always the end with an identifying mark, I.E. the curved end.
ashaw,
Don't worry. You did the PCB the way you have been trained to do. Not all of us are EE so that is why we sometimes get into trouble when we cannot just google a question (like a silkscreen).
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