Dumb question about "matched transistors"

[Locrian99]

It’s always the shipping…

 

[BryGuy]

Just found this video helpful

Haven’t seen one of Paul’s videos in a while. He seems to have stopped posting them for whatever reason. Really good stuff though.

 

[andare]

Haven’t seen one of Paul’s videos in a while. He seems to have stopped posting them for whatever reason. Really good stuff though.

Yes, so much so that that's Eric, the other owner of the company who's been making videos on the channel instead of Paul. Something about Paul needing to take care of other parts of the business and Eric being more knowledgeable on technical matters.
This channel was my gateway drug into pedal making. I hope Paul resurfaces soon.

 

[MichaelW]

I'm using a DCA75 with SMD adapter.

I tested a few MMBFJ201s similar to how you did it, then tested them again with the SMD adapter and got completely different measurements.

Ok, so I have another dumb question.

I soldered 8 of the 10 MMBF2n5457's I had tested earlier with my "pencil eraser" jig (same batch as the ones I sent you) on adapter boards and measured them. Not getting anything close to -1.4v. They were all in the positive numbers....around .4xx to .8xx range.

I'm a bit confused about this JFET matcher board.

This is what the board looks like. Note that it only has 2 unmarked "DMM Test Points".



Here's the schematic...



Again, it only says DMM1 and DMM2.

I've been assuming that DMM 1 is where I should have the COM lead of my meter and DMM2 is where I am measuring the voltage with the red lead of my DMM. Obviously, flipping them gives me negative readings.

Now I'm confused, do I have this backwards?

 

[fig]

I think you need 2 DMMs No, that’s another method, sorry.

I think you my have the leads reversed yes. You are reading the voltage/current from the opamp output that is trying to look like a 10kΩ .

 

[MichaelW]

Ok, I think I may be doing this backwards. Looking again at RG Keen's article and also looking at tagboard effects layouts for a Vero based matcher, I think COM or negative lead of my DMM should be at the DMM2 testpoint of the schematic above. Ugh....stretching my brain here about stuff I don't understand. Can someone confirm? TIA!

 

[Deperduci]

I see where you might be getting confused, the pin 3 of IC ALSO being listed as positive.. other than the +/_ are the numbers the same when you test either way? If you're getting the same readings numerically but only pos/neg are swapped.. I wouldn't worry to much, the last time I built a pge board I clipped my negative to the "hot" pin of the power jack and the numbers still matched regardless of the +/- inidcator, but that might be my odd ball luck

 

[MichaelW]

Yah that’s what’s confusing me. But I think I got it now after looking at some of the other tag board layouts.

 

[MichaelW]

Ok just for sh*ts and giggles, I built it out today. Tried the MMBF5457's, didn't work, very light phasing.
Then I tried 4 random MMBFJ201's, slightly more phasing (I think) but still doesn't work.
Sigh, guess I'll have to wait for the matched set. Oh well......
(This was with a 200k trimmer, I couldn't find a 250k.)

 

[MichaelW]

ok, more dumbassery abounds.....I forgot that the 2n5952 pinout was reverse from the 5457's and J201's.
I turned the 201's around and it works now. Actually pretty decent phasing. (Randomly chosen MMBFJ201's)
I'll try the MMBF5457's again oriented correctly later today and compare.

 

[RobertJay]

Hey all, is this still a place to chat about this? I too am in the same boat. I have about 25 UNMATCHED 5952's, 12 of which went into a BYOC Lil phaserpcb to crappy results. I want to test them to match them and just don't know if I HAVE TO build the tester, us the KEEN tester I made for Germanium tests, or if I can simply use mt TC-1 component tester. When I do use the mini tester, I get 2 readings listed as what looks like @Vg. One reading =202mV and another that says 421mV. Actually here's what the screen reads for a test...
Idss=2.5mA
Id=0.29mA
@Vg=201mV
Id=0.00mA
@Vg=421mV
Are any of these values what I need to match my quad sets? Why do I have a tester and NOT know what it's telling me? I'll look these readings up in case this thread is dead. Thank!

 

[giovanni]

You need to use the RG Keen method. Chuck posted a really good explanation: https://forum.pedalpcb.com/posts/178703/

 

[DeadAirMD]

Man oh man do I love a slow phaser into an overdrive