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Dead short between pins 1 and 2 of IC3. Can this be correct?
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Joined: 7/29/2008(UTC)
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Hi, I've just started populating an IVY. Added 9 resistors and the diode.
I realised that I hadn't checked the value of R13-R16 before installing
and so checked them in situ. When I did, I found R16 was reading as zero
ohms. Disconnecting/desoldering R16 only, I seem to have a dead short between
pins 1 and 2 of IC3. Can this be correct? I've looked for a solder bridge
and can see none.
I've installed:
R9-R12
R14-R16
R21,R22,R23
D1
R14 reads 2k in situ, R16 reads 2k unsoldered.
Regards, Mike.
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Rank: Administration
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No, it should not be a short.
Time to ferret it out.
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Rank: Member
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Joined: 7/29/2008(UTC)
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Location: UK
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Thankyou Russ.
Removed and replaced the chip, seems to measure fine now.
Regards Mike.
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Rank: Member
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Joined: 7/29/2008(UTC)
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Location: UK
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When I say 'removed and replaced the chip' I did mean replaced the same chip having checked for shorts. The IVY is up and running, fed by a Zhaolu AD1852. Too early to make any real judgements, but I'm listening SE and it's sounding good. I want to allow myself and the IVY more time and try balanced etc. A fun build, as a built unit it looks really professional too. All three op-amps run very warm, IC2 might be a bit hotter than the others, I can hold my fingers on them, but not for too long. Is this OK? Power supply is +/-14.8V. The IVY is in Opus configuration but with the on-board filter of C1-C4 and R17-R20 omitted. I am running an external low pass (3.3k,220pF) pre the IVY. I make current draw 86mA (measured across a 2.2R placed in the supply line) Regards, Mike. Edited by user Sunday, November 16, 2008 10:44:08 AM(UTC)
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Rank: Member
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Joined: 7/29/2008(UTC)
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Location: UK
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Hey guys,
I'm probably wrong about this, I don't recall anyone
mentioning it before, I am a complete amatuer, and I
make frequent mistakes.
I've been reading my OPA1632 datasheet and if I've
figured it out correctly, the maximum power dissipation
for the SO-8 package is 0.74W @ a reasonable 25C ambient.
With a typical quiescent current of 14mA per channel and
a +/-15V supply this would easily be exceeded.
I've reduced my supply to +/-10.5V!
Listening single-ended from the OPA1632s' outputs and it's
sounding pretty good.
You'll probably tell me it's not an S0-8 package now.....
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Hello, it is perfectly fine to run the IVY at 15V rails. I have always done so. :) This is well within spec. It runs pretty warm, but nothing close to the max temp. All is well, no need to reduce the suppply. :) I would not omit the filter section around the OPA1632!!! Reducing the value of the cap is ok, say 240pf(or around that) and then you can also just use a jumper at R17-R20. Cheers! Russ Edited by user Tuesday, November 18, 2008 7:13:16 AM(UTC)
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Rank: Member
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Joined: 7/29/2008(UTC)
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Location: UK
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OK, thanks Russ Quote:I would not omit the filter section around the OPA1632!!!
Reducing the value of the cap is ok, say 240pf(or around that) and then you can also just use a jumper at R17-R20. Sorry, I must have misunderstood this in the IVY Manual?: Quote:NOTE: Some users may wish to try different filter schemes. The filter can actually be omitted on the Opus. Presumably the caps presence is also for 'compensation' as with the LM4562? I'm afraid I don't understand and haven't researched the concept but it does seem quite stable as is. Regards, Mike. Edited by user Tuesday, November 18, 2008 1:34:09 PM(UTC)
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Rank: Administration
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Joined: 10/24/2006(UTC)
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Don't get me wrong mate, omitting the filter caps will work just fine. I am just saying I would personally not do it. :) This is just from experience. It does make the job of filtering at the next stage a bit easier. :) Cheers! Russ Edited by user Tuesday, November 18, 2008 1:40:51 PM(UTC)
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
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The caps around the BAL/SE opamp should absolutely not be omitted BTW. :) They are needed to compensate the opamp.
Cheers!
Russ
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Rank: Member
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Thanks again, and thank you for a great product.
I've still got a couple of filter combinations I want to try
amongst other things, so obviously I will try it your way!!
I do actually have a lot of faith in your design decisions,
they make sense to me. It all sounds plenty good as is!!
Regards, Mike.
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Dead short between pins 1 and 2 of IC3. Can this be correct?
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