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LektroiD
Joined: Aug 23, 2008 Posts: 1018 Location: Scottish Borders
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Posted: Fri Feb 10, 2012 8:38 am Post subject:
CA3080 on ebay Subject description: ..are these fakes? |
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I ordered some CA3080E ICs from ebay in anticipation of a new project.
However, in the photo was a Harris IC, but what arrived wasn't. I don't know how to test these without building the next project, but the PCBs haven't even been manufactured yet.
Below are photos of the IC advertised and the ones that arrived.
the seller "vila_restor" has 100% feedback, but in the comments only people are saying how the delivery times were good, nothing about the actual product functionality.
I know he's a UK seller, but I'm wondering if he bought a stock batch from china and selling them on. These are certainly not the Harris ones advertised.
Quote: | The current stock is Harris branded. |
...unless Harris logo changed to a letter 'i'
Has anyone else had experience with this seller?
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Seller's photo of Harris CA3080E |
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My photo of what actually arrived |
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This image has been reduced to fit the page. Click on it to enlarge. |
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LektroiD
Joined: Aug 23, 2008 Posts: 1018 Location: Scottish Borders
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Posted: Fri Feb 10, 2012 8:52 am Post subject:
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I found a photo of an intersil (which is what the logo appears to be on the chips that arrived). However, it looks quite different...
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J3RK
Joined: Jun 05, 2006 Posts: 123 Location: Seattle
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Posted: Fri Feb 10, 2012 11:11 am Post subject:
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That's the Intersil logo, which is who owned this design after Harris. I believe there is one more rev (visually) out there as well, but can't remember off the top of my head. That doesn't guarantee that they're good, but this is a proper part/logo. I have both of these types (Intersil/Harris) DIP package versions. There is also a metal can type, but I'm not sure what the markings on those are.
Edit: I see what you mean on the difference between the Intersil logos in those photos. I can take a look at what I have when I get home from work tonight, and tell you what mine look like. |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
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Posted: Fri Feb 10, 2012 11:20 am Post subject:
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I believe the logo is an "H". Looks exactly like some I have.
Ian |
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forshee
Joined: Dec 16, 2010 Posts: 46 Location: Hopkins, MN
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Posted: Fri Feb 10, 2012 12:13 pm Post subject:
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I got a few off ebay a few months ago. They were marked Harris and were DOA or fake. But to their credit they sent a new batch of chips with the Intersil marking and they seemed to work great.
I wouldn't be overly concerned about the graphics not looking exactly the same. My guess is that the silk screening is pretty easy to fake anyway. Breadboard something and see if it works. Smallbear sells them too by the way I think I'll go that route next time just to avoid the hassle. Good luck. |
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
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Posted: Sat Feb 11, 2012 7:33 am Post subject:
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I have a handful of archaic chips and there are vast differences between logos for the same company and the text.
As advised by forshee, test them to see. _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Green Dungeon Alchemist Laboratories |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Sun Feb 12, 2012 1:38 am Post subject:
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is there a simple circuit to test these? or just whip up a vca and test them "in situ"? |
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roman_f
Joined: Jul 03, 2007 Posts: 63 Location: Moscow
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forshee
Joined: Dec 16, 2010 Posts: 46 Location: Hopkins, MN
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Posted: Thu Feb 16, 2012 1:01 pm Post subject:
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There are a bunch app notes in the data sheet if I recall. Otherwise just drop in anything you have socketed. |
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magman
Joined: Feb 04, 2009 Posts: 363 Location: Liverpool, UK
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Posted: Sun Feb 19, 2012 6:01 am Post subject:
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I had a suspicion that I have also been recently supplied with some fake Harris CA3080E's so today I built a test circuit on my breadboard that I found from one of the Elektor Formant articles (Actually the 24dB VCF, as this works best with 4 matched 3080's).
The circuit works great, but I appear to have been supplied with 30 fakes from what I had hoped was a reputable supplier (I've dropped them a note to see how they will respond to this issue, so I won't name them at present).
I'm going to knock up a Veroboard version of this test circuit, as I expect it will be very useful in the future. I'll post it on here once I've worked it out, but check out the Elektor article if you want to test your own IC's more quickly (It was in the Elektor Formant book that is available from a few sources on the web)
Regards
Magman |
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magman
Joined: Feb 04, 2009 Posts: 363 Location: Liverpool, UK
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Posted: Sun Feb 19, 2012 1:28 pm Post subject:
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OK, here goes with a first draft of the OTA Tester on Veroboard.
I've only just drawn this, I will be building it and testing it later.
The Original text from the Elektor Article is as follows:
Quote: | A test circuit for OTA's is attached. This should be fed with a sinewave of about 2V peak-to-peak (or 0.7V measured on an AC Voltmeter) from a signal generator or from one of the VCO's. The output should be monitored on a 'scope or AC Voltmeter. With a control current of 100uA, measured on the multimeter in series with R5, the output voltage should be between 0.7V and 1.3V peak-to-peak.
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The circuit can also be used to check the linearity of the transconductance v.control current characteristics of the OTA's, e.g. doubling the control current should double the output of the test circuit and halving the test current should halve the output.
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A few issues I found when testing this on my breadboard is that most of my multimeters don't actually measure down to 10's of uA, so you may have to be a little less precise in this measurement depending on your meters. Also, I was able to test this with a multimeter and a scope, but if you haven't got a scope you are likely to need 2 meters, as the uA meter needs to stay in-circuit for the tests. This uA meter connection is also quite critical, if you don't have a good connection here, the circuit won't work.
Last but no means least, you can mount VR1 off board if you want. I actually used a 15-turn preset here, for a degree of precision when setting the test current, though this was a little slow to change when testing the linearity.
Hope you find this useful.
Magman
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Veroboard layout for Elektor OTA Tester |
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hexadec
Joined: May 08, 2015 Posts: 11 Location: Lands End UK
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Posted: Sat May 16, 2015 9:02 am Post subject:
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Hellooooo
I know this is an old thread but I came here and fell for it so I thought I'd make sure no one else does...
The ICs shown above are reversed (IC1 should be the OTA under test and IC2 the 741/071).
Other than that the circuit layout works fine.
Been lurking here for a while now so hi everyone |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Tue May 19, 2015 7:10 am Post subject:
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Welcome and thanks for the good tip!
I bought a bunch of them on eBay in Germany, and one of them didn't work in a circuit I built (can't remember which circuit), plugged in another one (I got a bunch of old stock items from a colleague of mine ), and it worked.
Been sitting on those 20 odd 3080's ever since meaning to either chuck them or test them. Maybe one of these days. |
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hexadec
Joined: May 08, 2015 Posts: 11 Location: Lands End UK
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Posted: Tue May 19, 2015 7:21 am Post subject:
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Thanks for the welcome mate.
I think I've been quite lucky...I've bought quite a few from China and so far they all work and are not fakes. |
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magman
Joined: Feb 04, 2009 Posts: 363 Location: Liverpool, UK
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Posted: Sun Jun 14, 2015 11:47 pm Post subject:
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hexadec wrote: | Hellooooo
I know this is an old thread but I came here and fell for it so I thought I'd make sure no one else does...
The ICs shown above are reversed (IC1 should be the OTA under test and IC2 the 741/071).
Other than that the circuit layout works fine.
Been lurking here for a while now so hi everyone |
Thanks for spotting this
To be honest, I never got round to building this, I just left the circuit on one of my breadboards.
I have managed to accumulate a stock of good 3080's though. In fact I might give some of them as a raffle prize for the next Synth DIY meeting in Cambridge next month.
All the best
Magman |
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hexadec
Joined: May 08, 2015 Posts: 11 Location: Lands End UK
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Posted: Mon Jun 15, 2015 12:20 am Post subject:
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Quote: | I never got round to building this |
I did...it works great
You can buy CA3080s in an SOP8 package from China cheap as errrr chips... (about 0.13p each)
...or you can buy DIP8 versions for about 0.65p each.
Just the usual problem of waiting for a month before you get them. |
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jurekprzezdziecki
Joined: Mar 22, 2016 Posts: 68 Location: warsaw
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Posted: Thu Dec 12, 2019 6:45 am Post subject:
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I had some issues with 3080s bought on eBay. 2 faulted and few hours of the testing circuit to find it. Will do the test circuit for sure before I will plug the IC next time. |
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hexadec
Joined: May 08, 2015 Posts: 11 Location: Lands End UK
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Posted: Thu Dec 12, 2019 8:39 am Post subject:
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jurekprzezdziecki wrote: | I had some issues with 3080s bought on eBay. 2 faulted and few hours of the testing circuit to find it. Will do the test circuit for sure before I will plug the IC next time. |
I always buy from Aliexpress. They are usually cheaper and I really have had no problems with 100s of orders. It's just the wait for deliveries that can be a problem if you're impatient like me. |
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AlanP
Joined: Mar 11, 2014 Posts: 746 Location: New Zealand
Audio files: 41
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Posted: Thu Dec 12, 2019 9:33 pm Post subject:
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Another option is to wire up half a LM13700. |
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vladosh
Joined: Aug 02, 2010 Posts: 659 Location: macedonia
Audio files: 46
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Posted: Fri Dec 13, 2019 4:54 am Post subject:
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i got CA3080 from Ali in smd and TH and both work fine ,also some PT delay chips, LM4250 and so on..never had an issue _________________ http://synthacks.blogspot.com/ шематикс |
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AlanP
Joined: Mar 11, 2014 Posts: 746 Location: New Zealand
Audio files: 41
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Posted: Fri Dec 13, 2019 7:24 am Post subject:
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My understanding is that Ali is a bit like Amazon or Ebay -- many vendors, all operating under one website. So, different vendors have differing reliability. |
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