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My_Ref Fremen Edition GB (14th GB)
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Old 4th July 2020, 04:13 AM   #111
madisonears is offline madisonears  United States
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Joseph detected the change, which I requested years ago.

Dario, you found a way to do it, and I thank you for this and all your efforts.
Please invoice me for one pair of fancy R3's. I'll be happy to use them in this new build. I agree that the Caddocks have outstayed their welcome.

Peace,
Tom E
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Old 4th July 2020, 12:18 PM   #112
lehmanhill is offline lehmanhill  United States
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I've been looking and looking and apparently not terribly observant. Are we talking about the extra mounting hold in the middle?
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Old 4th July 2020, 02:59 PM   #113
madisonears is offline madisonears  United States
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Dario,

Please be aware of the new R3/heatsink position in relation to chip mounting hole. It was always problematic. I can't tell for sure, but the new orientation looks like it might be even worse. If the resistor could be moved slightly off-center, mounting 3886 to heatsink would be much easier.

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Tom E
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Old 4th July 2020, 05:31 PM   #114
ClaveFremen is offline ClaveFremen  Italy
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My_Ref Fremen Edition GB (14th GB)
Quote:
Originally Posted by lehmanhill View Post
Great work, Dario.

It looks like it might be tight, but is it possible to include a hole for the old TO-220 R3 spacing? For example, I know that Pete is using the Ohmite TO-220. It's not a big thing if its not possible.
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Originally Posted by MassBoost View Post
Good idea, that would give people more options if possible.
Hi Jac,


I will look at it but anyway a TO220 resistor can still be mounted bending its leads...

Quote:
Originally Posted by MassBoost View Post
Speaking of C1 and C2, when did you make the change to the 470uF decoupling caps as the schematics I've been looking at has 220uF caps, and how much of an effect did they have on mid frequencies?

If I remember correctly when BOM has been revised for 1.6.


Too much time passed I don't remember which difference made but it was introduced following other LM3886 designs and it did improve perceived performance.

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Originally Posted by Joseph K View Post
Had a close look. I find it very nice. Don't see problems so far.. Maybe still overlooking something but really looks good..
And.
Hi George,
nice to read

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Originally Posted by Joseph K View Post
COMPLIMENTI per i 500..!
Thanks
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Originally Posted by Joseph K View Post
Maybe one thing..
When one is not using C9, because of the FET input opamps, normally it should be shorted out.
But.. At this moment R10 could be just directly connected to the top (red) ground plane.. If You would just create a clearence in the ground plane solder mask, somewhere beside the R10 pin.. Then a zero ohm resistance could be plced there or simply a solder blob / bridge, directly connecting R10 to that sensitive ground..
Something like this?:


My_Ref Fremen Edition GB (14th GB)-c9_byp-jpg
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Originally Posted by Joseph K View Post
I see an extra hole..?
Quote:
Originally Posted by lehmanhill View Post
Are we talking about the extra mounting hold in the middle?
Yes
Quote:
Originally Posted by madisonears View Post
Joseph detected the change, which I requested years ago.

Dario, you found a way to do it, and I thank you for this and all your efforts.
You're welcome

Quote:
Originally Posted by madisonears View Post
Please invoice me for one pair of fancy R3's. I'll be happy to use them in this new build. I agree that the Caddocks have outstayed their welcome.
Done
Quote:
Originally Posted by madisonears View Post
Please be aware of the new R3/heatsink position in relation to chip mounting hole. It was always problematic. I can't tell for sure, but the new orientation looks like it might be even worse. If the resistor could be moved slightly off-center, mounting 3886 to heatsink would be much easier.
Following build guide suggested mounting method it's not problematic at all, even with the new bigger resistor and heatsink.


My_Ref Fremen Edition GB (14th GB)-buildguide-jpg

In any way this arrangement permits shorter return path for the feedback network and to not impair, as much as possible, current return from the LM3886.
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File Type: jpg buildguide.jpg (157.0 KB, 302 views)
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Old 4th July 2020, 11:29 PM   #115
Panelhead is offline Panelhead
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[QUOTE=MassBoost;6263252
Speaking of C1 and C2, when did you make the change to the 470uF decoupling caps as the schematics I've been looking at has 220uF caps, and how much of an effect did they have on mid frequencies?[/QUOTE]

Years ago, maybe 2003 or so, Mauro childed me for this change. Said the value was for proper overload recovery. Said from testing this was the largest value that clipped properly. He saw these caps as bypass caps for the the 10,000 ufd reservoir caps.
Those versions used SIP package general purpose rectifiers. With dual bridge fast rectifiers this may be addressed.
I never told him about the 22 ufd FM caps I soldered directly to the LM3886 power pins. They were under the board out of sight.
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Old 5th July 2020, 12:48 AM   #116
ClaveFremen is offline ClaveFremen  Italy
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My_Ref Fremen Edition GB (14th GB)
Default Reminder: last day(s) for partipating the GB

This sunday or at worst next monday I will order boards so who's interested should hurry up!


Same thing for the last 4 participants that still have to pay.
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Old 5th July 2020, 03:36 PM   #117
MassBoost is offline MassBoost  United States
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Quote:
Originally Posted by Panelhead View Post
Years ago, maybe 2003 or so, Mauro childed me for this change. Said the value was for proper overload recovery. Said from testing this was the largest value that clipped properly. He saw these caps as bypass caps for the the 10,000 ufd reservoir caps.
Those versions used SIP package general purpose rectifiers. With dual bridge fast rectifiers this may be addressed.
I never told him about the 22 ufd FM caps I soldered directly to the LM3886 power pins. They were under the board out of sight.
Heh nice, out of sight out of mind...
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Old 6th July 2020, 05:35 PM   #118
lumlum is offline lumlum  Germany
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You can also clamp the LM3886.
With a piece of 6mm brass flat bar.
But there are also extra clamps for this attachment.

In my Solton SPA 150 it is also solved this way, only then is the brass rod used for quicker heat dissipation.

Jeff Rowland attached the LM3886 to the Model112 with a brass flat bar.Click the image to open in full size.
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Old 6th July 2020, 05:40 PM   #119
lumlum is offline lumlum  Germany
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When using the mounting bracket, the force distribution is uneven.
This is such a small problem what the LM3886 brings with it because it has a bad warm hotspot.
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Old 7th July 2020, 12:08 AM   #120
ClaveFremen is offline ClaveFremen  Italy
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My_Ref Fremen Edition GB (14th GB)
Default Slight delay, worth it, though.

Since design have been modified significantly I'm double checking everything, fixing text orientation, optimizing small details and also introduced support for both lead spacing variants for z-foils (3.81 and 5.08 mm lead spacing).


Boards should be ordered by next wednesday.



My_Ref Fremen Edition GB (14th GB)-immagine-jpg
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