SOLVED Marigold....

[comradehoser]

Build #6 is the problem child.

Issue: attenuated fuzz, very low volume. Doesn't quite get to unity with volume pot cranked.



Q1: bc107 w/hfe 398
Ie: 2.4 mA
Ube: 640mv

Q2: bc109c w/hfe 674
Ie: 3.2 mA
Ube: 663 MV

Q3: Polish oc140 clone
Hfe: 76.2
Ic: 1.0 mA
Ube: 71mV
ICEO: 0.20m

Maybe someday somebody will explain to me the significance of those measures and how to figure leakage.

What I've done: reflowed all solder points including offboard, recleaned board, rechecked components, swapped r4 15k from 1/8w to 1/4w, replaced Q3 and D1. No dice.

Readings:
9V in: 9.38v

Q1:
c: 3.978
b: 0.626
e: 0.033

Q2:
c: 3.992
b: 0.688
e: 0.050

Q3:
c: 0.310
b: 0.184
e: 0.002

D2 is sending 4.51v.

please assist this poor lost Canadian in making his nice fuzz

 

[Harry Klippton]

Double and triple check your component values, especially your resistor values in this area since it looks like your Q3 collector voltage is low

 

[Mcknib]

Is D1 the correct way around or is it one of those Russian ones with the band on the anode if it's the wrong way around that'll mess up Q3s biasing

What's your Polish transistor I've never seen NPN Polish germaniums is it a TG series

 

[comradehoser]

Is D1 the correct way around or is it one of those Russian ones with the band on the anode if it's the wrong way around that'll mess up Q3s biasing

What's your Polish transistor I've never seen NPN Polish germaniums is it a TG series

Correct, it's a Russian the right way 'round. You can see the pellet. Somebody once observed that the symbol for diode literally is a diagram of a germanium pellet at the end of the current "arrow".

Now hold on, now... NPN? That might be the issue right there. For some reason, I was convinced, like really *convinced* the 2 silicon transistors were NPN and I needed a PNP for Q3. (My memory of the OC 140 designation kept slipping and I was looking up random OC 14X pinouts, so maybe that has something to do with it.) In that case, I have a bitching top hat NPN Ge transistor I can put in there this evening, and we'll see what's up.

 

[comradehoser]

Double and triple check your component values, especially your resistor values in this area since it looks like your Q3 collector voltage is low
View attachment 74091

I will triple double-check that, but I'm pretty sure the values are good, unless it's my greatest fear... a resistor whose code can be read backwards and forwards.

 

[Harry Klippton]

Q3 indeed should be npn. And you certainly could misread resistor color codes from the wrong direction

 

[Mcknib]

Meant to say I checked all values and orientation they looked good to me

The OC140 is NPN I'm on a mad quest for NPN germaniums so I've bought a few recently

Saying that there is some dude selling them as PNP on ebay I didn't tell them coz I thought they're cheap I'll get me a few

 

[comradehoser]

the black oval top-hat kind are great. Can't recall their typical hfe, though.

 

[comradehoser]

... Put in the npn oval top hat transistor (2n169) [edit: 89 hfe]

Yet another episode in what happens when you put the right components in correctly.... It, uh, works.

Imagine that.

Any advice on the D1 GE diode biasing deal?

 

[comradehoser]

And also, thank you very much to Harry Klipton and McKnib for your time and attention in poring over my little fuzz and helping me solve this. Very much appreciated!

 

[benny_profane]

Any advice on the D1 GE diode biasing deal?

Check out this thread for tons of great information about this circuit:

Sola Sound Yellow Hybrid Tone Bender

Hi folks, I have one of the yellow hybrid tone benders from Macaris/Sola Sound—curious if anyone is interested in attempting a trace? It's a fave of Kevin Shields/My Bloody Valentine, and I think it's more closely related to the 3-transistor Supa/Jumbo than the mki/ii/iii TBs...

forum.pedalpcb.com

 

[comradehoser]

And you certainly could misread resistor color codes from the wrong direction

But how do you know the right direction for sure, especially if there are brown bands on both ends????

 

[benny_profane]

There should be something indicating how the colors should be read. Either the value bands will be grouped together with tolerance spaced apart, the entire code will be offset on the body of the resistor, or the tolerance band will be thicker. It’s certainly not always the case that one of those are clearly happening.