EQD Sunn Life Pedal Help

[HighSolstice]

I've built this layout from the link below but only the boost section is functioning.  I'm not getting output when the dirt side is engaged.  A few changes have been made to the layout that you can see documented in the comments section but this version seems to be verified.  Here are my measurements and photos.  I'm currently wondering if I've messed up on the switch wiring.

http://dirtboxlayouts.blogspot.com/2019/10/earthquaker-devices-sunn-o-life-pedal.html?m=1

LM308N:
Pin 1 - 6.58V
Pin 2 - .02V
Pin 3 - 2.26V
Pin 4 - 0V
Pin 5 - .06V
Pin 6 - .02V
Pin 7 - 8.88V
Pin 8 - 7.82V

Q1 - PF5102
D - 8.88V
S - .7V
G - 0V

Q2 - 2N5089
E - .22V
B - .76V
C - 6.49V

Q3 - 2N3906
E - 3.9V
B - 6.48V
C - 1.64V

Q4 - 2N5089
E - .48V
B - .14V
C - 8.88V

Q5 - PF5102
D - 8.88V
S - .7V
G - 0V

Q6 - BS170
D - 6.12V
G - .68V
S - .11V

[antonis]

Not sure if it's the exact circuit but let's have a reference for checking..



Q1 is an input buffer (Source follower) so its Source should be biased at about halfway the power supply rails..
(first point to check..)

Q2 is an amp with its Collector biased at marginally OK voltage..

Q3 is a phase splitter so its Emitter/Collector should be biased on equal voltage "distance" from power supply rails.. e.g. for an Emitter voltage of 1.5V say, Collector should stay on 7.5V..
(second point to check..) 

Q4 is also an (octave) output buffer so its Emitter should also stay at halfway the power supply rails
(third point to check..)

Q5 is also a buffer so see what should stand for Q1..

Q6 is a Booster which seems to be marginally OK..

IC1 is a complete mess..
Its output is heavily loaded (possibly shorted somewhere/somehow) so misbias at pin 3 should be ignored for the time  being..
ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM   ALARM
P.S.
Before checking anything else, verify proper items orientation

[Elijah-Baley]

Indeed the LM308N voltage seems messed up.
Here you can see the voltage of a original Rat:
https://www.diystompboxes.com/smfforum/index.php?topic=111505.msg1026396#msg1026396
It could be help you.

[antonis]

Some suspect points to look at..
(lower left area points are already tried guilty by Eye Attorney..) 

[temol]

Also check:


T.

[HighSolstice]

I traced those tracks with a razor and checked the suspect points for continuity with a multimeter, I think they all check out.  I did notice that my 4.7uF cap was reversed, I've fixed that and have new readings on the LM308N but it's still behaving the same.

Pin 1 - 4.96V
Pin 2 - 4.26V
Pin 3 - 2.36V
Pin 4 - 0V
Pin 5 - 2.26V
Pin 6 - 4.47V
Pin 7 - 8.96V
Pin 8 - 6.17V

[highwater]

Those voltages for the '308 look much, much better. Pin 3 is rather low, but it's what we'd expect to see if your multimeter has a low input impedance.

---

I suspect your 2n5089s (and possibly your 2n3906) have different pinouts than usual, and that the somewhat-OK-looking voltages on Q2, Q3, and Q4 are just a fluke (I *wish* that pun were intentional).

Here's my thought process:

At a first-level sanity check, Q3's voltage look swapped-around but otherwise good-enough... *except* that Q3's base actually *is* connected to Q2's collector, like it should be, which makes me wonder if the vaguely-reasonable voltages are only a co-incidence. Could it be a problem with Q2?

Well, Q2 looks OK too... not great, seems like the base-emitter junction is being driven harder than it should be, but it looks like you should get *something* through.

Q4 is a bit of both: Doesn't look great, but it looks like you should still be getting *something*... AND the voltages are swapped around.

Well, what if the pins go ECB instead of EBC? Q2 becomes an NPN with the base connected to power through 22kΩ (R7) and the collector connected to ground through 47kΩ (R6)... that's basically a forward-biased diode... if we make some simplifications because it's late here and math is hard now, that gives us somewhere around 2/3 supply, plus-or-minus a diode drop, which is close-enough to what we measure on what's *supposed* to be Q2's collector and Q3's base...

...and testing (rather than looking-up) the pinout of the transistors, even if the only ones you have are soldered to the board, is almost definitely easier than doing any more math. I don't know if your meter has a diode-test function, but if it does, it *should* work even with the transistors soldered to the board.

[HighSolstice]

I don't believe they have different pinouts from what is on the layout.  Both should have EBC pinout according to their respective datasheets.  I checked another of each from the batch with the diode setting, I'll post my findings below but they seem okay.

2N3906 - PNP
Pin 1 to Pin 2 - 763
Pin 2 to Pin 3 - 761

2N5089 - NPN
Pin 1 to Pin 2 - 758
Pin 2 to Pin 3 - 754

[HighSolstice]

Is the positive leg of D7 supposed to be in row R or S?

[Elijah-Baley]

Your LED is in the right place.

[HighSolstice]

I've traced my circuit with an audio probe and these are the places I can hear signal coming through when both the boost and rat are engaged.  Maybe this will help identify a row I need to look at.  Not hearing anything that sounds like a rat yet.  Anywhere that is unmarked has no signal, here's the color coding I used for the rest:

Red - Power
Black - Ground
Tan - Can hear signal but it is almost inaudible
Yellow - Quiet signal but not a struggle to hear, may be close or equal to bypass volume
Light Green - Sounds like the bypassed signal
Dark Green - Sounds amplified/louder

[temol]

You should transfer this onto the schematic. It would definitely help to troubleshoot the board.

[antonis]

I don't believe they have different pinouts from what is on the layout.  Both should have EBC pinout according to their respective datasheets.  I checked another of each from the batch with the diode setting, I'll post my findings below but they seem okay.

2N3906 - PNP
Pin 1 to Pin 2 - 763
Pin 2 to Pin 3 - 761

2N5089 - NPN
Pin 1 to Pin 2 - 758
Pin 2 to Pin 3 - 754

2N3906 - PNP
Pin 1 to Pin 2 - 763
Pin 2 to Pin 3 - 761 You should read OPEN

2N5089 - NPN
Pin 1 to Pin 2 - 758 You should read OPEN
Pin 2 to Pin 3 - 754

In any case, as long as Base is pin 2, you should read one diode drop from 2 to both pin 1 & 3 (n-p-n) or open (p-n-p)

[HighSolstice]

antonis,
I took these readings for the NPN keeping the positive lead on the center and for the PNP keeping the negative lead in the center.  If I do not flip the leads and just measure the pins from left to right I return one open reading for each as you said. 

temol,
I will attempt to do this later with a printed schematic but it may take me some time, currently my understanding of where I should and should not hear signal and what it should sound like in each state is pretty limited.  I am figuring I should be picking up signal at all of the rows leading to pots as well as the clipping switch, is this correct?  Is it normal for the signal on Octave 2 and 3 to be barely audible or does this indicate a problem beforehand?  Could this indicate a bad potentiometer or am I wrong to think that?  I haven't run into any faulty or fake components in any of my builds yet but I expect I will eventually and may have a difficult time narrowing it down.  When I began audio probing and found that much of the board has no signal I started to develop more questions than answers.

[highwater]

D1 and D2 are backwards. On the layout, too.

[Elijah-Baley]

Yes, it's true!
Weird, this layout is built and verified.
In the link in the first topic there's some pictures: https://imgur.com/a/d3TXGqK

[HighSolstice]

The cathodes of each should be facing towards the Base of Q4 then?  I've flipped D1 and D2 around on mine but it's not working yet so I updated my audio probe map and readings, the signal coming out of the Octave pot is stronger now though.  The signal coming out of pin 1 of the the LM308N is very splatty and gated, seems like there's something else going wrong either with or around my IC but I haven't figured out what yet.  The voltage on pin 1 seems incorrect now and I'm not sure why.

LM308N:
Pin 1 - 0.21V | Pin 8 - 6.86
Pin 2 - 4.11V | Pin 7 - 8.79V
Pin 3 - 2.30V | Pin 6 - 4.30V
Pin 4 - 0.00V | Pin 5 - 2.61V

[highwater]

Yes, cathodes towards Q4's base.

It may not completely work yet, but progress is progress.

Anyway, now I'm out of my element again. All I can say for sure is that pin 1 is measuring far too low now*. It seems that it should be close-to but maybe slightly lower than pin 8, and both of them should be within a diode-drop-or-two of V+.

I don't really have any ideas that don't boil-down to "look for more shorts and/or weak solder joints".

---

*: I fell down an internet hole wondering what the "don't worry about it" range for pins 1 and 8 really are, and found some worthwhile links.
A 1994 datasheet for the LM308. Shows an internal schematic (spoiler: it's not the only one).
A moderately technical (and math-free) history of IC op-amps.
A detailed summary of how opamps do what they do (and what they look like inside), based around photomicrographs of the inside of an LM108.

The relevant conclusion was that, despite the internal differences, all of those varieties of LMx08 opamps seem likely to drive pins 1 and 8 to similar voltages, with pin 1 perhaps a diode-drop-and-change below pin 8... much like your first set of IC voltages. In retrospect, your second set of voltages was already reading lower on pin 1 than I'd expect.

Edit: Some erroneous statements struck-out. See below.

[PRR]

I don't follow. Comp A is about 0.7V below the positive rail. Comp B tracks the output very closely.

A very low pin 1 suggests a blown IC.

In general you do NOT want to be poking these pins because they are easy to blow-up.

[highwater]

I don't follow. Comp A is about 0.7V below the positive rail. Comp B tracks the output very closely.

You are correct... I suspect that last-night-me first assumed that the inputs and output are *always* the same voltage, then mis-counted V_BEs and/or got pins 1 and 8 backwards.

Sadly, my Rat clone doesn't have a '308, otherwise I could have just measured it's (presumably different) pin 1 voltage and not made a fool of myself.

A very low pin 1 suggests a blown IC.

In general you do NOT want to be poking these pins because they are easy to blow-up.

If it were my build, I'd have to ask: are there any measurements you would suggest taking before throwing a new opamp into that socket?