Author Topic: Harbinger 1.5 Build - phase issue  (Read 265 times)

aruberus

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Harbinger 1.5 Build - phase issue
« on: February 02, 2020, 01:07:10 AM »
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
« Last Edit: February 03, 2020, 03:21:47 PM by aruberus »

aruberus

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Re: Harbinger 1.5 Build - phase issue
« Reply #1 on: February 03, 2020, 06:35:28 AM »
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

« Last Edit: February 03, 2020, 03:21:00 PM by aruberus »

madbean

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Re: Harbinger 1.5 Build - phase issue
« Reply #2 on: February 04, 2020, 04:08:23 PM »
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.
I own madbeanpedals (duh). I am part owner of Function F(X).

aruberus

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Re: Harbinger 1.5 Build - phase issue
« Reply #3 on: February 06, 2020, 05:04:23 AM »
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

aruberus

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Re: Harbinger 1.5 Build - phase issue
« Reply #4 on: February 20, 2020, 02:01:53 PM »
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