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 Forum index » DIY Hardware and Software » YuSynth
VCO tracking problem...fake LM394's?
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Satindas



Joined: Mar 26, 2011
Posts: 39
Location: uk

PostPosted: Mon Dec 12, 2011 2:05 am    Post subject: VCO tracking problem...fake LM394's? Reply with quote  Mark this post and the followings unread

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

PostPosted: Mon Dec 12, 2011 2:54 am    Post subject: Reply with quote  Mark this post and the followings unread

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

PostPosted: Mon Dec 12, 2011 6:29 am    Post subject: Reply with quote  Mark this post and the followings unread

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 Embarassed )
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

PostPosted: Mon Dec 12, 2011 6:51 am    Post subject: Reply with quote  Mark this post and the followings unread

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

PostPosted: Mon Dec 12, 2011 8:51 am    Post subject: Reply with quote  Mark this post and the followings unread

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... scratch

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

PostPosted: Mon Dec 12, 2011 10:49 am    Post subject: Reply with quote  Mark this post and the followings unread

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: 411
Location: Raleigh NC

PostPosted: Mon Dec 12, 2011 11:14 am    Post subject: Reply with quote  Mark this post and the followings unread

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

PostPosted: Tue Dec 13, 2011 8:38 am    Post subject: Reply with quote  Mark this post and the followings unread

I managed to source the LM394's in the UK at £4.99 . Very Happy Very Happy
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 Wink
Cheers
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Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Tue Dec 13, 2011 9:31 am    Post subject: Reply with quote  Mark this post and the followings unread

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

PostPosted: Sat Dec 17, 2011 6:28 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

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yusynth



Joined: Nov 24, 2005
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Location: France

PostPosted: Sat Dec 17, 2011 10:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Thalassa. How much does cost a LS318 ?
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Yves
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Thalassa



Joined: Jan 27, 2006
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Location: Spain
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PostPosted: Sat Dec 17, 2011 11:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Yves, it cost more or less 5€. The LS318 is also available in other packages. I choose the TO-78 instead P-DIP because they didn't have it in ROSH version and I didn't want to go surface mount.

Here you can see the datasheet

http://pdf1.alldatasheet.com/datasheet-pdf/view/84164/LINEAR/LS318/+5_Q75UHGLECycxVYt.+/datasheet.pdf

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defog



Joined: Aug 24, 2011
Posts: 113
Location: Philadelphia

PostPosted: Fri Mar 23, 2012 6:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

Satindas wrote:
I managed to source the LM394's in the UK at £4.99 . Very Happy Very Happy
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 Wink
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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synchroma



Joined: Oct 18, 2011
Posts: 69
Location: London

PostPosted: Fri Nov 08, 2013 7:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Just read this thread too late.

After a long period of frustration, I built a simple test circuit for dual transistor chips, and tested every BJT pair that I've been trying to use in an expo converter. The SSM2220 chips I bought from Farnell are OK, but I've wasted months it seems with my set of 15 -counterfeit- LM394 and SSM2210 chips, all sourced from China.

I am, right now, fuming at the injustice Evil or Very Mad but at least I have learned my lesson the hard way. Now I'm trying out a number of options:

First, I bought some MAT12s from uk.farnell.com. Not cheap - £18 a piece (that's about $25)

I'm in the UK, so after some hunting I found a source for Linear Systems LSIT120 - http://www.micross.com/ - but you can search the map on the LS home page to find yours wherever you are: http://www.linearsystems.com/distributors.php

I had to register to buy on Micross - a LOT cheaper: £2.52 a piece Smile

I'm also going to check out the PMP4201V from Digikey/NXP semiconductor. Cheap, but SMD so I'll have to make some adapters.

So, I've spent a lot of money, but at least I know now
1) I am not going mad
2) I'm probably not completely STUPID and incapable of electronics and
3) Never buy ICs from China

Cheers
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synchroma



Joined: Oct 18, 2011
Posts: 69
Location: London

PostPosted: Fri Nov 08, 2013 8:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Hmmm. It could be tricky with the PMP4201V chips I bought. Still, it's worth a shot! Top Copper, 600DPI Very Happy
The PMP4201V is reversed, so Q2 becomes Q1 of the pseudo-LM394 and vice-versa. It won't make any difference to how it works, but it was much easier to make the connections that way. The * indicates pin 1 of the PMP4201V.


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gdavis



Joined: Feb 27, 2013
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PostPosted: Fri Nov 08, 2013 1:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

I just noticed that mouser has ssm2212, apparently an improved version of the 2210. I plan on trying them out next time I put an order in.
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elmegil



Joined: Mar 20, 2012
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PostPosted: Fri Nov 08, 2013 1:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

You'll need an SMT -> DIP adapter if you're using it with an existing circuit.

Schmartboards makes some; I have a few but have not actually applied them yet.
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synchroma



Joined: Oct 18, 2011
Posts: 69
Location: London

PostPosted: Fri Nov 08, 2013 4:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

SSM2212 is supposed to be better, and I believe it's still available and Ray Wilson's MFOS VCO has a board design that will take an LM394 or an SSM2212. Worth looking at.

PMP4201V was a random googling. I haven't actually received any of these yet, but I went on a very thorough shopping spree today. My plan is to etch a few of these and solder via pins through the holes, or even just whack the SMD footprint on to some existing expo designs I have made and see how good it is. It's cheap! And if I can get some good tracking ranges with them then I think they might be a good, really cheap substitute with the right adapter (design above). NXP claim a maximum 2mV Vbe matching. Those tiny 3300ppm/K tempcos might just fit on them OK with enough thermal grease.

SSM2212 should be easier to do, but it's frustrating for me that you can get quite a lot of stuff in the US that's really hard to get here in the UK.

But the Linear Systems chip seems more appealing for the boards I've made already. I bought all three bits in anger today (25xPMP4201V, 10xLSIT120, 3xMAT12). Having etched and built some expos and VCOs already with the duff chips, the LSIT120 will fit into them.

PMP4201 is an experiment, but one that is yet to arrive in the mail from the US. The LSIT120s will arrive in 3-4 weeks, so I'm left with a few MAT12s which will be here on Monday I think. After a couple of months of frustration I'm desparate to get on Smile

Last edited by synchroma on Fri Nov 08, 2013 6:06 pm; edited 1 time in total
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synchroma



Joined: Oct 18, 2011
Posts: 69
Location: London

PostPosted: Fri Nov 08, 2013 5:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

If you have etching facilities, here's an SSM2212 to SSM2210 adapter. 600DPI, Top Copper.


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synchroma



Joined: Oct 18, 2011
Posts: 69
Location: London

PostPosted: Wed Nov 13, 2013 7:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wha? I'm going to have to develop tiny eyes to get these into my synth Exclamation
(PMP4201V matched NPN transistor chips)


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Last edited by synchroma on Wed Nov 13, 2013 7:39 pm; edited 1 time in total
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synchroma



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PostPosted: Wed Nov 13, 2013 7:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

BTW here's a slightly better template for the SSM2212 adapter. Very Happy


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synchroma



Joined: Oct 18, 2011
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PostPosted: Thu Dec 19, 2013 6:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Tried this twice. First time I didn't cut the LaserStar prints out properly, and the tiny gaps between the SMD contacts were blurred into one because there was a tiny gap between the toner and the board. I've done it again with precision (and flatness) before I exposed the board, and I reckon these just might work! BTW electricdruid.com has some good advice for building SMD to DIP converters. Check it out! Will post once I have atempted to solder these things. Shocked


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synchroma



Joined: Oct 18, 2011
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Location: London

PostPosted: Thu Jan 02, 2014 7:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm putting this up here as well although I did post the pic on another thread - FYI.
This is the Ray Wilson VCO core without the waveshapers, using the LS120 from Linear Systems as a drop-in replacement for the LM394.

It's working...beautifully! It seems incredibly stable as well. The waveform just sticks to my scope lines like glue. And I have frequencies from less than 0.01Hz up to more than 50KHz - although I left out the resistors around the coarse and fine controls (and I'm running on +/- 15V).

Note: I'm using an LM4562NA op-amp as the voltage input amplifier (before the expo). Here in the UK it's cheaper than the OP275 (£1.68 each if you buy 10 from RS components) and has a 20V/uS slew and rail-to-rail output. A good discovery.

If there's interest I can post a board layout, but I need to annotate this with some component values...


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