Possibly hopeless small stone v2 build.

[Esppse]

I attempted an unverified vero layout and got it half working.

http://dirtboxlayouts.blogspot.com/2021/01/electro-harmonix-small-stone-v2.html?m=1

Schematic:
http://www.montagar.com/~patj/smlstone.gif

With the color switch down, we have proper phasing, but very low output.

Color switch up, the thing goes haywire and starts to sound like a 60s sci fi high frequency sweeping:

https://youtube.com/shorts/QdPTHDjmgn8?feature=share

I checked the component value and location more times than I can count.

--Voltages--
Upper left LM13700:
1: 1.25   16: 1.26
2: 0.20   15: 0.20
3: 3.56   14: 3.56
4: 3.56   13: 3.55
5: 4.72.  12: 4.74
6: 0.00   11: 8.98
7: 4.72   10: 4.74
8: 3.55   9: 3.56

Upper right LM13700: same results
1: 1.25   16: 1.26
2: 0.20   15: 0.20
3: 3.56   14: 3.56
4: 3.56   13: 3.55
5: 4.72.  12: 4.74
6: 0.00   11: 8.98
7: 4.72   10: 4.74
8: 3.55   9: 3.56

Bottom LM13700:
1: 0.00   16: 1.13
2: 0.25   15: 0.27
3: 0.14   14: 5.3-7.2
4: 0.14   13: 5.4-7.2
5: 0.25  12: 2.3-2.4
6: 0.00   11: 8.98
7: 0.00   10: 0.00
8: 0.18   9: 0.19


Q1
E: 2.85
B: 3.28
C: 8.32

Q2
E: 8.97
B: 8.34
C: 5.43

Q3
E: 1.83
B: 2.37
C: 8.97

Q4
E: 1.30
B: 1.82
C: 5.47

Q5
E: 6.81
B: 6.81
C: 6.48

Q6 same as Q5,
E: 6.81
B: 6.81
C: 6.48

Many values move with the LFO. Does anything here look out of place?

[antonis]

Unfortunately, I can't find a schematic with 6 BJTs..

[Mark Hammer]

That drawing really feels like a slapdash attempt to mimic a 5-OTA bufferless unit, like the CA3080-based one posted at General Guitar Gadgets, using LM13700s.  If you have the trio of LM13700s already, consider making a "Ropez" (black Ross phaser), from the Tonepad site.  It aims for, and is based on, the Small Stone, with variable feedback.

[TeleHB]

Try flipping Q6 to cbe.

[Kevin Mitchell]

Try flipping Q6 to cbe.

Good catch!
I had pulled this up a few times today trying to find an error for the OP. That's definitely one.

[Esppse]

Just tried flipping Q6, it actually sounds the same flipped either way, same volume drop, and high frequency sweeping.

Could it be a dead chip or transistor?

[Esppse]

Ahhh it came to life! I switched out for different 2N5088s, kept the Q6 flipped as advised.

Thanks very much!!! 

[TeleHB]

Pleased to hear you got it sorted!

A while back, I worked up a v2 adaptation along the same lines as that layout, and I like it. I used this schematic:

The 13700 substitution is direct in the phase stages, but not in the LFO, which uses the CA3094's "sink" output (pin 8 ). The two extra NPNs solve that problem by replicating its output buffer.