Yet more dumb stuff preventing a working pedal

[Mark Hammer]

I pulled out a non-working (hence never boxed) Ross/Ropez board that I'd never been able to get off the ground despite many previous successes.  Replaced a bunch of things, but no dice.  Finally traced the problem down to one or two resistors in the LFO who tarnish resulted in a cosmetic solder joint, which wasn't a real solder joint.  Pulled them out, scraped them with a blade until shiny, then re-installed, and bingo bango, I had sweep.

The second nemesis is a Tonepad Scrambler/Revolcador board.  This one was driving me nuts because I could get signal up to the input cap, but no further.  I thought maybe it was the same issue with tarnish component leads, but nope.  After much trial and error, I discovered that, unlike the datasheet and EVERY single pinout drawing I was able to find via a Google image search, MY 2N5306 transistors had an ECB pinout, rather then EBC.  At least the one in Q1 position does.  I have signal continuity up to the "output ends of the diodes, but the "clean/boost" signal is MUCH MUCH louder than the octave signal, and there is barely any octaving.  I tried the EBC pinout and the ECB pinout, but no go.  I'm beginning to think that one of these 2N5306 transistors is the "proper" pinout and the other isn't.

Now, normally, after determining pinout with datasheets and diagrams, I confirm by testing out hfe in my meter.  But Darlington transistors are weird.  Stick em in the meter as EBC and you get an hfe reading exceeding the meter's range.  Flip 'em around and insert as ECB or BCE and you still get an hfe reading above the meter's range.  Since I can't rely on datasheets OR meter readings, how would I be able to tell if the ones I'm trying to use are EBC or ECB?  This is driving me a little nuts.

[GibsonGM]

I'm sure there is some 'test', Mark (and I don't know it), but - have you thought of assembling a basic circuit, like a bazz fuss using a darlington, and seeing what you get with it oriented one way vs. the other? The higher output being the correct pinout (as long as you got the base right). 
Just a thought.

[Mark Hammer]

That's a reasonable strategy, Mike.  I hate to start another circuit, but I hate beating my brains against the wall of a nonfunctional one even more.

[Matthew Sanford]

[mozz]

Just checked my 2n5308s and ECB on 3 different testers, gain of 21000. These are TO98-3 package.

[Mark Hammer]

Swapped out the 2N5306 units for a pair of MPSA14s I had.  They correspond to their pinout.  Problem solved and sweet sweet nasty octaving is in progress.

Thanks for the suggestions, folks.

[PRR]

The Base-Emitter breakdown of most Silicon transistors will be 7 volts. (So 14V on Darlingtons.)

Collector-Emitter breakdown is of course 30v 40v or more.

And forward "breakdown" is OTOO 0.6v.

Find a 24V power supply, a 10k resistor, and a voltmeter. Try a modern well-documented part first.

Beware that the "low noise" parts will be less-low after breakdown.

And if you are trawling parts from 1960, you still had Symmetrical and Germanium parts to fool you.

[Elektrojänis]

I think I once found datasheet for BC549 that had the pinout reversed from what the ones in my parts bin had. I dug up some more datasheets and some of them matched the parts I had. It's no wonder I really don't trust anything.

Maybe you could make a simple DC-amp circuit for testing purposes with a 4-pin header for the transistor under test like on the multimeter. Then just measure how it biases. if it seems sensible then you have the pinout correct. Measuring just DC would save the trouble of feeding it any AC test signal.

[bloxstompboxes]

A simple test I find is to use the diode test on your multimeter. On a NPN, the positive lead on the base and the negative on an emitter or collector will give you around 600 ohms or so. Opposite lead placement necessary for a PNP. Though does not tell you which pin is the emitter or collector, only which is the base. But now you have a 50/50 chance of getting it right the first time.

[GibsonGM]

Is that gonna work on a Darlington, tho? 

[ElectricDruid]

That's a reasonable strategy, Mike.  I hate to start another circuit, but I hate beating my brains against the wall of a nonfunctional one even more.

How hard is your head? How hard is the circuit?

Ok, so now...which one's gonna crack first?!? 

Honestly, sometimes I think beating your head against it until it *does* crack is literally the only way. It's just a damn pity it has to *hurt* so much!! Let's just say "I feel your pain"
 

[GibsonGM]

The best kind is the one you beat your head over repeatedly, can't understand what's going on, and then...it just works.  You don't know why, or how, but it does...   

[Phend]

The worst kind are those that worked last month suddenly don't work now.

[soggybag]

You need one of these:

https://www.amazon.com/Pocketable-Multifunctional-Backlight-Transistor-Capacitor/dp/B07X5YS1JN/ref=asc_df_B07X5YS1JN/?tag=hyprod-20&linkCode=df0&hvadid=692875362841&hvpos=&hvnetw=g&hvrand=5604563617845481055&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031950&hvtargid=pla-2281435177618&psc=1&mcid=6f3f63d2e576305bbb1e18e6f57caa30&hvocijid=5604563617845481055-B07X5YS1JN-&hvexpln=73&gad_source=1

For $18 it tells you the type, labels the pins, provides hfe and leakage.

[bloxstompboxes]

Is that gonna work on a Darlington, tho? 

Yeah, you're probably right. lol.

[Focalized]

You need one of these:


For $18 it tells you the type, labels the pins, provides hfe and leakage.

I have a similar one with a battery. It often doesn't read some mid-high gain transistors. 2N5088/89, BC10x, etc. They read as resistors. It's good for most. And for resistors and caps. Had a Atlas DCA at some point. It's costly to buy another and I'm not getting into again costly GE transistors anymore.

[GibsonGM]

Is that gonna work on a Darlington, tho? 

Yeah, you're probably right. lol.

Yeah, about once in every 10 posts, LOL