Hi,
Ive built 2 identical Harbinger 1.5 pedals. One sounds awesome and the other lacks its chorusy/phasing quality.
Ive checked all Voltages and compared all LDR's, Caps and resistors. They are all the same on both boards.
Of note Q10 is reading 15 - 16 volts on all pins. This does not line up to the docs.
Where should I look to see what is causing the big difference in the chorus/phasing sound?
(more info in following post)
Thanks
Adrian
Some more useful diagnostic information which hopefully helps identify the problem.
Using a sine wave generator as source I scoped the outputs of each LDR at the following points.
Oscilloscope was set to dual channel so I could compare Dry and Wet.
Identifying each board as 'A' and 'B' the results were quite different in comparison.
LDR1 R19 A 180deg phase shift B 180deg phase shift
LDR2 R25 A amplitude modulation and phase shift B amplitude modulation and phase shift
LDR3 R31 A -180deg phase shift B -180deg phase shift and amplitude modulation
LDR4 R37 A -180deg phase shift and slight pitch B -180deg phase shift and slight amp mod
So What would be causing 'A' and 'B' to have these different phase shift qualities.
Im assuming A is correct but thats only because i prefer the sound.
Both pedals were set to 'vintage' and 'chorus'.
thanks,
Adrian
No doubt there are a couple issues happening here.
1 - Your "+18v" too low. You should be reading b/w 17-18v on Q10 collector. Unlike stock Univibes, the Harbinger runs all the audio at 18v and leaves the regulated 15v to the LFO section only. First I'd compare your PS voltage supply reading w/o load then compare it to what drop you have after D1 with it powering the circuit. I'm guessing you're getting something closer to 8v on pin8 of the LT1054 based on your actual "+18v" reading. Point being, if your are having 16+v hit the 15v regulator then it may be draining excess current as it tried to regulate the voltage with an insufficient supply.
2 - Fixing 1 may resolve the Q10 problem or not. Just to be extra sure I visually checked the current batch of boards @ Q10 and also used a multimeter to check for continuity errors. No issue on the boards at all. But, maybe check for continuity errors on C, B and E of Q10 of your build with the board un-powered to be sure.
Thanks Brian,
With the Power off I have no continuity between any of the pins on Q10. Is that correct?
I should also clarify that the Harbingers are working as expected even with the spurious voltage readings on Q10 and Q12. As per my original post Im curious why one sounds better than the other as per the different scope readings below. The one I like the sound of better may actually be the 'faulty' one. Does one of the Scope descriptions sound more correct than the other?
SineWave input @ 300Hz
LDR1 R19 (5.19v) A 180deg phase shift B 180deg phase shift
LDR2 R25 (5.16v) A amplitude modulation and phase shift B amplitude modulation and phase shift
LDR3 R31 (5.19v) A -180deg phase shift B -180deg phase shift and amplitude modulation
LDR4 R37 (15.8v) A -180deg phase shift and slight pitch (DC Offset?) B -180deg phase shift and slight amp mod
R16 top phase shift and slight pitch (DC offset?)
R16 bottom phase shift and pitch (DC offset?) + Amplitude modulation
Im running with the voltage doubler.
Voltage In 8.98v
D1 output 8.69v
Other voltage readings below. All boards are roughly the same readings.
Q1 2N5089 Q2 2N5088
C 2.03 C 4.06
B 1.37 B 2.03
E 0.92 E 1.45
Q3 2N5088 Q4 2N5088
C 12.85 C 16.45
B 4.06 B 5.19
E 3.41 E 4.83
Q5 2N5088 Q6 2N5088
C 12.19 C 16.4
B 4.83 B 5.19
E 4.23 E 4.18
Q7 2N5088 Q8 2N5088
C 12.23 C 16.43
B 4.80 B 5.18
E 4.20 E 4.82
Q9 2N5088 Q10 2N5088
C 12.20 C 16.42
B 4.82 B 15.88
E 4.23 E 15.47
Q11 MPSA13 Q12 MPSA13
C 14.96 C varying
B varying B varying
E varying E varying
Q14 2N5457
C 16.4
B 0.98
E 0.0
LM7815CT
in 16.37
gnd 0.0
out 14.95
LT1054CP
1 1.39
2 4.75
3 0
4 0
5 0
6 2.57
7 1.44
8 8.68
Many thanks,
Adrian
Ok , So i fixed the Voltage issues on Q10 finding that I have previously measured and labelled my 68K resistors at R40 wrong when they were actually 680 Ohm !!
I still have the mysterious sound difference between the builds and am curious as to where I should look at component swapping. Should I be looking at the LDR's (unmatched), Caps or other and which of the 4 stages should I be looking at that would effect this?
Thanks