matching transistors - DIY

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delayed
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matching transistors - DIY

Post by delayed » Mon Apr 08, 2013 2:25 am

Hi,
I am looking into this and see Ian Fritz, October 2010 article and Ray's MFOS article, Transistor Matching 101 under the Synth-DIY 101 tab within his website. The MFOS shows a little circuit and a larger GO no GO circuit.

Has anyone made up one of these? If using Ian's how do you swap the emitter leads easily. Setting up a switch perhaps?

Does anyone have some images of their testing bread board setup? Or better suggestions than these two examples?

I would like to see what other people are doing to match their transistors.

Thanks,

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Post by roglok » Mon Apr 08, 2013 5:56 am

I built both on stripboard, the simple MFOS and Ian's. Both work fine, but Ian's is a lot simpler to build.

I used DIP sockets for testing the transistors. Left is Ray's, right Ian's:

Image

Ray's is missing the power connector - was short of those and harvested it for a module :oops:

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e-grad
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Post by e-grad » Mon Apr 08, 2013 6:27 am

Do these sockets work?

I had built a noise module with a socket for the noise source (transistor) some time ago. However, the transistor didn't made sufficent contact to make it feasible.

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Post by roglok » Mon Apr 08, 2013 6:41 am

e-grad wrote:Do these sockets work?

I had built a noise module with a socket for the noise source (transistor) some time ago. However, the transistor didn't made sufficent contact to make it feasible.
The machined sockets do work - not sure about the cheap ones. They actually sit in there quite firmly... Also keep in mind that this is only a temporary circuit...

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Post by qfactor » Mon Apr 08, 2013 10:18 am

Roglok: so you used the 8-pin IC sockets for the transistors? How do the E-C-B pins of a transistor plug in?

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Post by roglok » Mon Apr 08, 2013 10:48 am

qfactor wrote:Roglok: so you used the 8-pin IC sockets for the transistors? How do the E-C-B pins of a transistor plug in?
You have to stretch them apart a little bit. I used a fine tipped permanent marker to designate the pinout directly on the stripboard. I can post a detail pic for you later...

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Post by roglok » Mon Apr 08, 2013 11:22 am

Image

I've inserted one transistor as illustration. If you look closely, you can make out the C B E markings next to the sockets. The lower two pins on each sockets are not used. You can see that one end of each 100K resistor has been bent upwards. These are the ends connected to the emitters and where I attach my DMM. Of course you could substituted this with something more robust, but since I don't match transistors every day it has worked just fine so far...

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Post by emmaker » Mon Apr 08, 2013 12:04 pm

You might check to see if the Ray Wilson circuit has the same flaw that the Moog schematic has. That is there needs to be a 10K resistor between the collector and emitter of the transistors in the PNP tester like the NPN one has.

Also keep in mind those sockets don't have a lot of insertion cycles. Might want to stack them 2-3 high and replace them as they wear out. That's a lot easier than having to unsolder and replace the one on the board.

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Post by J3RK » Mon Apr 08, 2013 12:06 pm

I have Ian's circuit permanently assigned to a small bread-board. Seems to do the trick quite nicely. I now only use monolithic matched pairs on rare occasions. I typically match them into groups, (by writing the values down and then grouping them by that) so I end up with maybe 5-6 good pairs after maybe 15-20 minutes of testing. That goes a fairly long way. :tu:
Last edited by J3RK on Mon Apr 08, 2013 12:11 pm, edited 1 time in total.

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Post by emmaker » Mon Apr 08, 2013 12:06 pm

Did a quick look for the Moog flaw and found this:

http://www.dragonflyalley.com/construct ... tching.htm

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Post by fonik » Mon Apr 08, 2013 12:07 pm

i made myself a professional one-off PCB, but anyways, i use machined SIL sockets (single row, cut to the correct length. and they work fine. actually a little bit too good. i have to insert the transistors carefully in order not to bend the legs...
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Post by roglok » Mon Apr 08, 2013 12:18 pm

emmaker wrote:Did a quick look for the Moog flaw and found this:

http://www.dragonflyalley.com/construct ... tching.htm
Bill and Will seem to be happy with DIP sockets, too :D

On a sidenote: I have previosuly matched pairs of 2N3904 and 2N3906 from the same batches - the VBE of almost all units tested was already within +/- 2mV of their counterpart without selection...

I guess this means that you can often just pop in any pair of modern transistors from the same batch and get satisfactory results...

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Post by kvitekp » Mon Apr 08, 2013 12:45 pm

Here's another version of MFOS Vbe matching tool: http://midisizer.com/vbe-matching, I still have a couple of spare pcbs.

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Post by delayed » Mon Apr 08, 2013 2:20 pm

kvitekp wrote:Here's another version of MFOS Vbe matching tool: http://midisizer.com/vbe-matching, I still have a couple of spare pcbs.
how much would you want for 1 or 2 of the pcbs? feel free to pm me. thanks,

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Post by jonbstevens » Mon Apr 08, 2013 3:03 pm

I breadboarded Ian's when i wanted matched transistors for for CGS DUSG's. I get close to 2 octaves in tune once i've got them trimmed correctly.

I'm not sure what sort of tuning to expect with unmatched transistors, but i'm pretty happy.

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Post by fonik » Mon Apr 08, 2013 3:04 pm

okay, while the MFOS circuit is called 'simple', Ian Fritz' circuit really IS simple. and there is no need for a precise voltage supply or matched resistors.
just a set of three resistors, a diode, and a DPDT on-on switch for each NPN and PNP transistors:

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Ian Fritz' Transistor Matcher by fonitronik, on Flickr
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Post by delayed » Mon Apr 08, 2013 3:13 pm

fonik wrote:okay, while the MFOS circuit is called 'simple', Ian Fritz' circuit really IS simple. and there is no need for a precise voltage supply or matched resistors.
just a set of three resistors, a diode, and a DPDT on-on switch for each NPN and PNP transistors:

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Ian Fritz' Transistor Matcher by fonitronik, on Flickr


Would you like to share your layout?

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Post by fonik » Mon Apr 08, 2013 3:16 pm

the eagle files, you mean? i would/could ask ian.
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Post by delayed » Mon Apr 08, 2013 3:22 pm

Yes, that would be good. Or just the SCH. I am guessing you set up the switch to swap the "e" and would like to see that part. A toner layout would even be better but I see that is asking a bit ++.

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Post by roglok » Mon Apr 08, 2013 3:37 pm

very handsome, matthias!

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Post by fonik » Mon Apr 08, 2013 4:11 pm

roglok wrote:very handsome, matthias!
and small !!! Will have to mount it to a panel .
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Post by J3RK » Mon Apr 08, 2013 4:38 pm

fonik wrote:okay, while the MFOS circuit is called 'simple', Ian Fritz' circuit really IS simple. and there is no need for a precise voltage supply or matched resistors.
just a set of three resistors, a diode, and a DPDT on-on switch for each NPN and PNP transistors:

Image
Ian Fritz' Transistor Matcher by fonitronik, on Flickr
That is nice! :tu: I'd much prefer to use that over my breadboarded version. :mrgreen:

It would be cool to make a "Builder's Utility Module" that contained this, a tuning calibrator for 1V/Oct and maybe 1.2V/Oct, and maybe some peak level indicators or something along those lines.

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Post by frijitz » Mon Apr 08, 2013 5:10 pm

fonik wrote:the eagle files, you mean? i would/could ask ian.
Of course, no problem. It's not like some clever invention, after all, basically just a Wheatstone bridge.

Ian

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Post by diablojoy » Mon Apr 08, 2013 5:13 pm

That is nice! I'd much prefer to use that over my breadboarded version.

It would be cool to make a "Builder's Utility Module" that contained this, a tuning calibrator for 1V/Oct and maybe 1.2V/Oct, and maybe some peak level indicators or something along those lines.
seconded
an accurate note indicator would be very useful
It probably wont happen today but if it does it definitely wont go smoothly.

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Post by qfactor » Mon Apr 08, 2013 6:04 pm

diablojoy wrote:
That is nice! I'd much prefer to use that over my breadboarded version.

It would be cool to make a "Builder's Utility Module" that contained this, a tuning calibrator for 1V/Oct and maybe 1.2V/Oct, and maybe some peak level indicators or something along those lines.
seconded
an accurate note indicator would be very useful
An A440 reference tone in this module would be good too! :tu:

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