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Old 14th February 2012, 01:12 PM   #461
swalter is offline swalter  Switzerland
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checked with the guys in the general O2 thread, agdr was so kind to answer promptly. The values in the BOM (1.0uF) are the correct ones for C6 and C7.

Stefan
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Old 14th February 2012, 04:22 PM   #462
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Hi Jokener,

could you please update the current delivery status? I've paid on January 1st, and now that all components seem to be available, the rest of the guys without the components are getting more and more nervous ;-)
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Old 14th February 2012, 07:42 PM   #463
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Quote:
Originally Posted by swalter View Post
checked with the guys in the general O2 thread, agdr was so kind to answer promptly. The values in the BOM (1.0uF) are the correct ones for C6 and C7.

Stefan
Oh well, as they are only there to filter the regulator from the AC supply it might only be an issue if you run it the amp off AC while using it. Any HQ cap should do,you mentioned getting some tants, they should be okay.

I am not going to change mine as I have no intention to use the AC input, but I will test the noise when I get a chance, doubt there would be enough hear though.

Tony
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Old 14th February 2012, 07:47 PM   #464
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I just rechecked the latest documentation pack on NWAVGUY's blog and he changed the BOM 0n 30 Nov to have the 6 caps all 0.22uf including C6 & C7 but as I said, I doubt it will matter much.
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Old 14th February 2012, 11:02 PM   #465
agdr is offline agdr  United States
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Quote:
Originally Posted by Roulston View Post
I just rechecked the latest documentation pack on NWAVGUY's blog and he changed the BOM 0n 30 Nov to have the 6 caps all 0.22uf including C6 & C7 but as I said, I doubt it will matter much.
The O2 spreadsheet BOM link under that documentation package link on RocketScientist's "O2 details" page is more recent, Dec 2011

https://docs.google.com/leaf?id=0B52...3Y2Iy&hl=en_US (download button in upper right corner)

but the capacitor thing isn't very important. That was a mod I cooked up due to the U6 datasheet, that RocketScientist adopted. Might only help in a few odd cases if U6 is overheating due to oscillation. The 0.22uF should be just fine for probably 99% of the builds. If someone is buying the caps for the first time go with 1uF if you want, since the price is about the same, but if you already have the 0.22uF no need to change unless you are having odd U6 heating issues.

Last edited by agdr; 14th February 2012 at 11:05 PM.
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Old 15th February 2012, 12:29 AM   #466
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Thanks AGDR, I had assumed the doc set in the blog was the most current.

You describe the change to prevent U6 going into oscillation, not U5? of do they both have the potential to oscillate and what the threshold condition that might make them do so?
Anyway, might be a problem if and only if you use the AC supply.

Glad for your clarification though, version control is a beach.
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Old 15th February 2012, 01:19 AM   #467
pby is offline pby  United Kingdom
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Jokener, you said you'd ship my order 2 weeks ago along with Roulston's. Could I get an update or something? I don't mean to nag you but it's not the first time I bugged you about it.

Regards
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Old 15th February 2012, 03:30 PM   #468
ecpc is offline ecpc  Hong Kong
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Jokener, package (1 pcb + 1 kits) well received in Hong Kong. thanks for putting this GB together.
btw, postage charged, :P
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Old 16th February 2012, 01:17 AM   #469
agdr is offline agdr  United States
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Quote:
Originally Posted by Roulston View Post
You describe the change to prevent U6 going into oscillation, not U5? of do they both have the potential to oscillate and what the threshold condition that might make them do so?
The issue is actually just with the negative regulator, U6. Turns out the positive regulator MC7812 and the negative MC7912 are asymmetric in that respect. Check out the value of "Co" in the application circuit in the lower right corner of the first page of the datasheets for the two:

http://www.onsemi.com/pub/Collateral/MC7800-D.PDF

http://www.onsemi.com/pub/Collateral/MC7900-D.PDF

Note on that first and second pages the two chips have very different circuit layouts, probably to avoid having to use a PNP pass transistor in the negative regulator, and hence the different values of "Co" to stabilize the chip. So since the negative regulator recommends the 1.0uF RocketScientist just upped both of them. If a regulator did start oscillating the net result would likely be abnormally large amounts of heating of just that regulator.

Last edited by agdr; 16th February 2012 at 01:27 AM.
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Old 16th February 2012, 01:34 AM   #470
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I had a look at the datasheet for the -ve version, and noted the advice, but they gave no narrative. Must The cap be that value? Just curious that they don't describe the condition and why that value, or for that matter why not add the cap to the internal of the reg as every example they gave required it. It might have one of those, " oh bugger" moments post production.

Tony
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