Help needed - troubleshooting Aion Refractor Kit

[Troshik]

Hello!
I am stuck troubleshooting this build: https://aionelectronics.com/project/refractor-klon-centaur-ktr-kit/

Problems:

IC1 and IC2 voltages are wrong
No sound, except in "true bypass" mode with effect off

Power source: wall wart at 9.46V

IC voltages:

IC3
P1: 9.46
P2: 4.80
P3: 0
P4: -4.46
P5: -9.08
P6: 4.70
P7: 6.13
P8: 9.46

IC1
P1: 2.71
P2: 2.71
P3: 2.02
P4: 0
P5: 1.10
P6: 2.55
P7: 1.31
P8: 9.46

IC2
P1: 16.14
P2: 0.48
P3: 2.80
P4: -9.08
P5: 2.80
P6: 4.29
P7: -7.44
P8: 17.19







Any help is very much appreciated!

[EBK]

Welcome to the forum!

Could you double check that the tantalum cap is oriented the correct way?  That has been an issue many many times with this circuit.

[Troshik]

Welcome to the forum!

Could you double check that the tantalum cap is oriented the correct way?  That has been an issue many many times with this circuit.

Thank you for the welcome and such prompt reply.

Here is a picture from the other angle:



How does it look?

[EBK]

Everything looks ok so far.  Could you post a pic of the underside of the board?

I didn't check all of the resistor values.

[Kevin Mitchell]

How about the bypass board?

-KM

[Troshik]

Everything looks ok so far.  Could you post a pic of the underside of the board?

Sure:

I didn't check all of the resistor values.

I checked them, cannot find any mistakes or shorts.

[Troshik]

How about the bypass board?

-KM

Yep:

[Troshik]

Does my soldering look OK? I know it looks tidy, but I'm worried whether I haven't been too thorough and overheated smth.

I was extra careful with the diodes though.

Is there a way to check for dead components without removing them from the board?

Thanks!

[Kevin Mitchell]

Well nothing seems dead. Familiarize yourself with the audio probe. It'll quickly guide you where your signal is going.

-KM

[EBK]

Was just about to comment on the soldering.  There are a few joints that have solder balls on them.  These could be places where the pad wasn't heated enough.  I'd reflow those.

[PRR]

> few joints that have solder balls on them.  These could be places where the pad wasn't heated enough.

Yes, balled-up solder is reason to reject. You Can Not Tell if the solder really "wet" both lead and pad.

I didn't squint these pix, but made a cartoon. Pretend you *want* to color a sidewalk. Drop ice cream on the hot sidewalk. The first, not-wet, picture, if you scrape it up fast there may be no stain. The second pic is starting to wet and will stain. The third pic is fully wet *and* you see the marshmallows, which in soldering means you can see the wetting on the wires.

[Troshik]

OK, Ill try to reflow the balls

Question - can liquid flux insulate the pad if it dries?

[duck_arse]

in this image, there is a 2M0 resistor 2 places above the diodes on the left. I look at the traces underside and see what appears to be an open trace, right at the inner pad. can you test continuity between this resistor and the bottom left red poly cap?

[Slowpoke101]

in this image, there is a 2M0 resistor 2 places above the diodes on the left. I look at the traces underside and see what appears to be an open trace, right at the inner pad. can you test continuity between this resistor and the bottom left red poly cap?

Certainly looks open circuit but it may just be some flux residue over the track. Picture below;


Now to change the subject. Your Vr voltage rail is too low. It should be about 4.5V. The Vr voltage is supplied via the voltage divider formed by R29 and R30. C18 is used for filtering the Vr rail (simplest explanation ). One end of R29 should connect to 9V and the other end connects directly to one end of R30 and C18. There should be 4.5V at this junction. Check the voltages and see what is going on.


The Vr rail is directly connected to IC2 pins 3 and 5. Remove IC2 and apply power, measure the Vr voltage again to see if it has come up. If it has then IC2 can be assumed to be toast - replace it. However Vr may still be too low with IC2 out - if that is the case IC2 should be OK.
The Vr rail does wander over the board a fair bit - it also goes to R2, R9, R8 and the GAIN pot (both segments ). It is possible that it may be shorting to another component so have a very good look to see if something is wrong.

[Troshik]

in this image, there is a 2M0 resistor 2 places above the diodes on the left. I look at the traces underside and see what appears to be an open trace, right at the inner pad. can you test continuity between this resistor and the bottom left red poly cap?

Certainly looks open circuit but it may just be some flux residue over the track. Picture below;

It was residue:


Unfortunately, I used liquid zinc chloride flux while soldering.

What happened I think, is that I applied that flux a little too carelessly. This residue also got covered by a layer of rosin of the solder wire. I suspect this mix could be conductive. Could you confirm?

To address this, I tried to clean the back of the PCB as much as I can, it looks cleaner now (see the pic).

The problem is that I am not sure whether there is any [conductive?] gunk left on the other side of the PCB, especially under the elements. I can see some rosin flux residue there, and I do not remember dousing that side in acid/salt based flux, although it might have seeped through the holes...

[Troshik]

Now to change the subject. Your Vr voltage rail is too low. It should be about 4.5V. The Vr voltage is supplied via the voltage divider formed by R29 and R30. C18 is used for filtering the Vr rail (simplest explanation ). One end of R29 should connect to 9V and the other end connects directly to one end of R30 and C18. There should be 4.5V at this junction. Check the voltages and see what is going on.


The Vr rail is directly connected to IC2 pins 3 and 5. Remove IC2 and apply power, measure the Vr voltage again to see if it has come up. If it has then IC2 can be assumed to be toast - replace it. However Vr may still be too low with IC2 out - if that is the case IC2 should be OK.
The Vr rail does wander over the board a fair bit - it also goes to R2, R9, R8 and the GAIN pot (both segments ). It is possible that it may be shorting to another component so have a very good look to see if something is wrong.

Below are IC voltages after the cleaning; with IC3 swapped to ICL7660S (original 1044 died); and with IC1/IC2 removed (and plugged back). PS is at 9.11 V.

IC3
P1: 9.11
P2: 4.55
P3: 0
P4: -4.54
P5: -9.09
P6: 4.61
P7: 7.06
P8: 9.11

IC1          (IC plugged in)
P1: 4.51   (1.64)
P2: 4.50   (1.64)
P3: 3.13   (1.48)
P4: 0        (0)
P5: 4.50   (2.58)
P6: 4.53   (2.62)
P7: 4.62   (2.89)
P8: 9.11   (9.08)

IC2           (IC plugged in)
P1: 4.64   (2.78)
P2: 4.50   (2.58)
P3: 4.52   (2.58)
P4: -9.09  (-8.67)
P5: 4.52   (2.65)
P6: 4.58   (2.65)
P7: 4.58   (2.50)
P8: 17.41 (16.36)

[Slowpoke101]

Zinc Chloride flux....Oh dear. That stuff is not suitable for electronics work at all. Rosin cored solder is the easiest to use and it leaves a residue that is not too much of a problem. Whereas zinc chloride flux leaves a corrosive residue that is corrosive enough to etch away the small copper tracks of the circuit board. The residue also absorbs water from the atmosphere (humidity ) and becomes a gooey mess (gooey being defined as a semi-gelled liquid ) which can become conductive over time. That flux is also known as "Spirits of Salt" or "Killed Spirits" or "Plumber's Flux" and is/was usually used on copper pipes and fittings hence "Plumber's Flux". It was usually made using hydrochloric acid (muratic acid ) that pieces of zinc metal had been dissolved in until the acid stopped bubbling when more zinc was placed in it. Very good at cleaning copper because it etched some of the copper away. The fumes from the flux are toxic and also corrosive - you really don't want to be using this stuff for electronics at all.

Now, what to do about it. Assuming that you have only recently assembled the board and the remaining flux has not had enough time to do too much damage just clean the board and the components (leave them soldered in ) with denatured alcohol (methylated spirits ). Clean it several times then hopefully no further corrosive action can take place.

Back to the problem. Your voltage measurements are interesting but can you redo them but leave IC1 and IC3 installed (remove only IC2 ). Good luck.

[Troshik]

Zinc Chloride flux....Oh dear. That stuff is not suitable for electronics work at all. Rosin cored solder is the easiest to use and it leaves a residue that is not too much of a problem. Whereas zinc chloride flux leaves a corrosive residue that is corrosive enough to etch away the small copper tracks of the circuit board. The residue also absorbs water from the atmosphere (humidity ) and becomes a gooey mess (gooey being defined as a semi-gelled liquid ) which can become conductive over time. That flux is also known as "Spirits of Salt" or "Killed Spirits" or "Plumber's Flux" and is/was usually used on copper pipes and fittings hence "Plumber's Flux". It was usually made using hydrochloric acid (muratic acid ) that pieces of zinc metal had been dissolved in until the acid stopped bubbling when more zinc was placed in it. Very good at cleaning copper because it etched some of the copper away. The fumes from the flux are toxic and also corrosive - you really don't want to be using this stuff for electronics at all.

Now, what to do about it. Assuming that you have only recently assembled the board and the remaining flux has not had enough time to do too much damage just clean the board and the components (leave them soldered in ) with denatured alcohol (methylated spirits ). Clean it several times then hopefully no further corrosive action can take place.

Back to the problem. Your voltage measurements are interesting but can you redo them but leave IC1 and IC3 installed (remove only IC2 ). Good luck.

Thank you, it was "not smart" on my part.
I will clean the board (I do have the denatured alcohol) and update the V readings.

[Troshik]

It lives!!! ))

After a thorough wash everything seems to work. All three pots work, there is gain/clipping, no weird unwanted noises.

IC voltages (power supply at 9.17V):

IC3
P1: 9.17
P2: 4.65
P3: 0
P4: -4.34
P5: -8.86
P6: 4.41
P7: 5.85
P8: 9.11

IC1
P1: 4.59
P2: 4.59
P3: 3.17
P4: 0
P5: 4.58
P6: 4.60
P7: 4.64
P8: 9.17

IC2
P1: 4.65
P2: 4.60
P3: 4.59
P4: -8.87
P5: 4.59
P6: 4.59
P7: 4.52
P8: 16.7

Are there any other checks I can/should do? Or should I just happily box it?

Lesson learned: don't use plumbing flux for soldering electronics! lol

[Slowpoke101]

Working! That is great news 

The voltages look good. Give it another clean just to be sure that all the zinc chloride is gone and then run the unit for an hour. If nothing goes wrong then box it up and call it finished.

Enjoy