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Satindas
Joined: Mar 26, 2011
Posts: 39
Location: uk
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 Posted: Mon Dec 12, 2011 2:05 am Post subject:
VCO tracking problem...fake LM394's? |
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Hi I have 3 YuSynth VCO's built which all work fine except for the fact that I only seem to be able to get good tracking over 2-3 octaves (at the most!). Could it be that I have fake LM394's ? I got them off some chinese ebayer for £4 each so no big loss if they ARE fake.
It seems that the SSM2210's are also like rocking horse shit and I'm therefore looking at starting my boards again with hand matched BC547's.
Or..... is there another alternative for the LM394/SSM2210 which I can stuff.
Cheers |
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MadScientist
Joined: Nov 28, 2011
Posts: 63
Location: Denmark
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| Posted: Mon Dec 12, 2011 2:54 am Post subject:
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There are two types of components available from China via eBay:
Fakes, which are not what they seem.
Rejects, which have been swept up from the factory floor after failing the requirements/quality control of the manufacturer/main contractor (usually a western brand name company).
Sorry about your misfortune. Hope you find a better solution (I went for the matched BC5xx transistors). |
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Satindas
Joined: Mar 26, 2011
Posts: 39
Location: uk
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| Posted: Mon Dec 12, 2011 6:29 am Post subject:
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| MadScientist wrote: | There are two types of components available from China via eBay:
Fakes, which are not what they seem.
Rejects, which have been swept up from the factory floor after failing the requirements/quality control of the manufacturer/main contractor (usually a western brand name company).
Sorry about your misfortune. Hope you find a better solution (I went for the matched BC5xx transistors). |
Hey thanks MadScientist.
That's pretty much what I'd guessed regarding the fake/sub-standard issue but for £4 each it was worth a shot. (I guess some of us just have to learn the hard way  )
I'm just waiting for a sourcing company to get me prices for genuine LM's but I'm expecting ££££££££'s.
So how is your tracking with the matched trannys? How close did you match them? |
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mark_olson
Joined: Oct 26, 2006
Posts: 177
Location: Lawrence, Kansas
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| Posted: Mon Dec 12, 2011 6:51 am Post subject:
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| MadScientist wrote: | There are two types of components available from China via eBay:
Fakes, which are not what they seem.
Rejects, which have been swept up from the factory floor after failing the requirements/quality control of the manufacturer/main contractor (usually a western brand name company). |
This is completely inconsistent with my experience. If this is true, which I seriously doubt, I guess I have been amazingly lucky because all of the components from all of the Chinese Ebay sellers I have purchased from have performed perfectly.
Mark |
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MadScientist
Joined: Nov 28, 2011
Posts: 63
Location: Denmark
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| Posted: Mon Dec 12, 2011 8:51 am Post subject:
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| Satindas wrote: | | So how is your tracking with the matched trannys? How close did you match them? |
My results were amazing to a point, where I am beginning to suspect I may have made some form of systematic error, or that my technique might be flawed in some other way. Starting out with 20x BC556A, I managed to get 9 pairs, with only two remaining outliers. Total spread across the whole lot was a bit more than 6mV. All pairs were matched to within 0.35mV in Vbe @ 100 uA Ic, and the two closest pairs are to within 20-30uV, on the same order of or less than the accuracy of my whole setup. Which is a ridiculous claim, to be honest... 
I will admit I tend to go overboard with testing of my stuff, but still...
| mark_olson wrote: | | This is completely inconsistent with my experience. If this is true, which I seriously doubt, I guess I have been amazingly lucky because all of the components from all of the Chinese Ebay sellers I have purchased from have performed perfectly. |
How do you know they perform perfectly? I am not trying to be a wise guy, did you actually *test* them in some way? Also, what parts are you referring to?
Please note I am not trying to claim all parts are fakes, or that they don't work. Only that a large part of them are *highly* questionable in their origin, and what testing they may - or may not - have passed at the factory. The number of suspicious cases I have come across over time is not negligible. Try asking your favorite local radio amateur, if he would build a radio power amplifier with RF transistors from China.
Then there are all the other surprisingly inexpensive power semiconductors with uncut leads in TO-220 cases (subcontractors to Linear Technology, I am looking at you).
Or electrolytic capacitors without the vinyl jacket, another Chinese specialty.
When even the US military gets it wrong...
Frank. |
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mark_olson
Joined: Oct 26, 2006
Posts: 177
Location: Lawrence, Kansas
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| Posted: Mon Dec 12, 2011 10:49 am Post subject:
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Frank:
Never mind. You are right, I have no idea if my SN76477 and SM2044 chips are performing up to spec. The circuits I have them in sound OK to me, and they sound the same from one to the next. But as you suggest, I do not test or verify their performance in any way.
Thanks for the reality check.
Mark |
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Mongo1
Joined: Aug 11, 2011
Posts: 392
Location: Raleigh NC
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| Posted: Mon Dec 12, 2011 11:14 am Post subject:
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For what it's worth, I've purchased several resistor and capacitor assortments from China (Cap-pro I think) and have been pleased with them.
I did a lot of spot checking on the resistors, and they were well within spec. I don't have a capacitor meter (c'mon Santa, I'm waiting) so I don't know about those. So far though everything has worked just fine.
I haven't bought Semi's from them, and probably won't.
Gary |
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Satindas
Joined: Mar 26, 2011
Posts: 39
Location: uk
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| Posted: Tue Dec 13, 2011 8:38 am Post subject:
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I managed to source the LM394's in the UK at £4.99 . 
Seems to be a reputable firm specialising in rare stuff so fingers crossed.
Just for the record though, I did come across these guys http://www.linearsystems.com/ who claim to produce a direct replacement for the LM394, the LS120. The website is not very helpful in trying to locate a European distributor but its maybe worth following up for those in the US.
Let us know 
Cheers |
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Mongo1
Joined: Aug 11, 2011
Posts: 392
Location: Raleigh NC
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| Posted: Tue Dec 13, 2011 9:31 am Post subject:
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| Quote: | | I did come across these guys http://www.linearsystems.com/ who claim to produce a direct replacement for the LM394, the LS120. The website is not very helpful in trying to locate a European distributor but its maybe worth following up for those in the US. |
I've been looking at that - they have a distributor called NAC Semi. I called them up and spoke at length with a sales rep. He's sending me a quote for 100 LS120s, a full line card, and SIX FREE SAMPLES.
My plan is to put those samples in some of my current boards and see how they do. I'll report back on what I find. I'd also be interested in hearing from any the current board developers that would like to get hold of one of these for evaluation purposes.
I'm fairly excited about this. The sales rep was very knowledgeable about the whole field of vintage audio parts, and says that's what his company is specializing in. This could be a good thing I think.
Note - I'll start a different thread for this.
Gary |
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Thalassa
Joined: Jan 27, 2006
Posts: 95
Location: Spain
Audio files: 5
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| Posted: Sat Dec 17, 2011 6:28 am Post subject:
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I have really good experience dealing with Linear Systems.
I'm using their LS318 ( equivalent to the Analog Devices MAT02 ) on my Corsynth C101 OTA Lowpass Filter and I'm really pleased with it.
_________________
http://www.corsynth.com |
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yusynth
Joined: Nov 24, 2005
Posts: 1156
Location: France
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| Posted: Sat Dec 17, 2011 10:46 am Post subject:
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Hi Thalassa. How much does cost a LS318 ?
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Yves |
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Thalassa
Joined: Jan 27, 2006
Posts: 95
Location: Spain
Audio files: 5
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defog
Joined: Aug 24, 2011
Posts: 107
Location: Philadelphia
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| Posted: Fri Mar 23, 2012 6:43 pm Post subject:
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| Satindas wrote: | I managed to source the LM394's in the UK at £4.99 .
Seems to be a reputable firm specialising in rare stuff so fingers crossed.
Just for the record though, I did come across these guys http://www.linearsystems.com/ who claim to produce a direct replacement for the LM394, the LS120. The website is not very helpful in trying to locate a European distributor but its maybe worth following up for those in the US.
Let us know
Cheers |
Sorry to bump an old thread, but I read this and the alarm bells started ringing from personal experience.
Hate to say it, but even the "reputable" dealers get their parts from the same place everyone else does = wherever they can source them from for the best price. Bottom line is that if there is money to be made and the part is rare, there are going to be fakes. I've yet to have been burnt in the 20+ Chinese part orders I've done on eBay, but believe it or not I HAVE been burnt by a domestic one in the USA. No one is safe from these counterfeit parts, they can change hands multiple times before getting in yours.
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The Phoenix Vertigo is my Electronic alias. Check out my songs on soundcloud : http://soundcloud.com/charles-stieg/ |
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