Aion Blueshift not chorusing

[Philthy]

Hi All,

My worst trouble-shooting nightmare has been realized - my Blueshift build was boxed and refused rock.

Symptoms:
1. Bypass signal  - fine.
2. Engaged signal  - no chorus effect. Sounds just like the bypassed signal with maybe a tad fewer highs (or more lows).
3. Unable to adjust both bias points. They are both reading 3.7v (off a 9.2v supply) and do not move when the trim pots are rotated.

Stock bypass.

I double checked IC and transistor orientation and reflowed pretty much all solder joints prior to boxing.

Will take some IC readings soon, but would appreciate any initial thoughts - even those relating to reducing the amount of IC readings as that is going to be a challenge!!

Disassembled pics



Preassembly PCB rear shots (not the best sorry)



THanks

[Timko]

Do you have an audio probe and a signal generator?  If so, can you probe both of the test points?  There should be audio coming through them.

I'm also facing problems with my Blueshift (the chorus isn't motionless) so I'll try to help after studying the schematic and probing my way through the circuit.

[Philthy]

Thanks Timko - yes I have a probe and sig gen and can confirm I have no signal on either bias test point. Looked for these on the schemo and can't spot them?? {EDIT: found them !!}

Voltages as follows - I couldn't get a read on some of IC3 and 4 as they were too difficult to probe.

(* denotes fluctuating voltage)

IC1 (OPA2134)   IC2 (NE570)   IC3 (MN3207)     IC4 (MN3102)   IC5 (TL072)    IC6 (TL072)   IC7 (TL022)
4.5                    0.8                0                        6.5                   4.6                3.6*              6.0
4.5                    1.8                non-read             3.0                   1.3*              3.3                3.2
4.1                    1.8                non-read             non-read           1.3*              3.3                2.5*
0.5                    0                   non-read             3.1                   0                   0                   0
4.5                    1.8                6.5                     4.8*                  3.3                1.7*               3.3
4.5                    1.8                3.0                     1.2*                  3.3                1.3*              3.3
4.5                    3.0                4.2                     4.3*                  3.3                4.5*              3.7*
9.0                    1.8                4.2                     6.0                    6.2                6.2                6.0
                         1.8
                         1.8
                         1.8
                         1.8
                         9.0
                         1.8
                         1.8
                         0.2
                         

IC12 (OPA2134) IC11 (NE570)   IC9 (MN3207)     IC8 (MN3102)  OPTO (H11F1)
4.6                    0.8                  0                        6.5                 1.3
4.6                    1.7                  3.1                     3.1*                0
4.6                    1.7                  4.1                     0                     0.3
0                       0                     6.1                     3.1                 4.5
4.6                    1.7                  6.5                     4.7*                 3.9
4.6                    2.9                  3.1                     1.3*                4.5
4.6                    2.9                  5.1                     4.3*
9.1                    1.7                  5.7                     6.1
                        1.7
                        2.9
                        2.9
                        1.7
                        9.1
                        1.7
                        1.7
                        0.8
               
Any thoughts appreciated.  Will do some probing tonight.

[gordo]

I'm finally getting around to populating my second board set so I'll hopefully have a finished one in house if I can be of any help.

[Timko]

Philthy, the points you can hear sound from should be the ones in the build doc to use for oscilloscope readings.  I'm curious if you're getting some signal through there that sounds kind of delayed.

Gordo, I have another thread about this pedal where my chorus isn't motionless (it sounds like the two parts aren't in sync) so I'd love to see the voltages off of someone's pedal that sounds like it works correctly.  I'm sure Philthy would as well.

[Philthy]

Thanks Timko and gordo.

Did a bit of probing last night with some interesting results.

The signal gets through both halves of IC1 (OPA2134) but cannot be read on either leg of C9 (10uF electro) that immediately follows IC1. ie: the signal is not getting to the first NE570 (IC2) and hence on to both sets of MN chips on the smaller pcb.

C9 is orientated correctly and I reflowed it with no change. I'd be surprised if there's an issue with the cap itself, but don't have a replacement at home at the moment.

In my layman's interpretation of the schemo, this explains why I am getting a non-chorused output ie: as the signal can bypass  IC1B and go on to IC12 and out.

Back to C9. I'm unfamiliar with the bold pairs of circles on the schematic. eg: just after IC1A and parallel to IC1B. Do these relate to the Opto bypass or two bypass options? If so, could this be a bypass problem? My bypass jumpering can be seen on last pic above. {EDIT: as can mu Optocoupler voltages}. I note some of these circles are labelled to correspond to the pcb hook ups.

Here's a link to the schematic: https://www.dropbox.com/s/51akvy8n0qy07g8/aion-blueshift-dimension-c-chorus-documentation.pdf?dl=1

[gordo]

Are you missing the 3 pin header at the top of the board?

[Philthy]

pic was taken before I added it - it's in

[Philthy]

Update - went back to basics and put away the sig gen and probe. Tested continuity around IC1 and IC2. There is no continuity between pin7 of IC1 and the +ve side of C9 Will jumper it from the back of the board and see what happens.

[gordo]

Rats, was hoping it was something that obvious.  Missing an entire header would be my type of mistake :-)

[EBK]

There is no way this is the problem, but....
In your pics, it looks like you missed a solder joint on one pad.  Probably just the lighting, but I had to ask about it for my peace of mind. 

Clock and LFO board, right above the "HI" of the silkscreened "BLUESHIFT."

I'm still haunted by missing a pad myself on that same board during my build. https://www.madbeanpedals.com/forum/index.php?topic=26365.msg255900#msg255900

[Philthy]

Thanks for that. That pic was taken before I went over all joints again, but I'll check it anyway.

I did follow that build thread of yours you crazy nutter .

[Bio77]

Update - went back to basics and put away the sig gen and probe. Tested continuity around IC1 and IC2. There is no continuity between pin7 of IC1 and the +ve side of C9 Will jumper it from the back of the board and see what happens.

What about pin 7 to R10, C8, or C7? 

[Philthy]

yeah will check that too, bit I think they'll be ok as that is the path for the output signal I'm getting?? ie: via IC12

[gordo]

I finally got the board finished. I blinked and it's mid February already. Mines working and sounds nice. I'll get it on the scope (I biased by pin 3 on each clock trimmed to 3.4v) to get rid of a very slight distortion and then get voltages on the chips.  I'll work on an audio sample as well.