Aion Refractor (Klon clone)Issues

[Big mike 1100]

Are these better pics?  I might have made them too big. The markings on the caps for C8 and C13 are 821J 100v and 391J 100v.  I thought they were right, but am not 100% certain as other builds seem to use the smaller ceramic caps

[aion]

Nope, those ones are correct. A lot of people just use MLCC ceramics because it's harder to find those odd values in film caps. But the original Centaur used films like you're using.

[Big mike 1100]

Thanks Aion! Appreciate the reply.

I'll check the other components.  What's the best procedure to check the gain and tone pots to make sure they are working? Is it an ohm test or more of a continuity test?

[Big mike 1100]

So I did some testing.  Not sure what this means, but here are some outcomes:

Each lug of the Tone Pot is much louder than the lugs of the two gain pots (all lugs have audio)

Several components only have sound on one of the legs- Tracing the path via the schematic:

IC2a pin 2 no sound
R22 Right leg has tone, not left (Per PCB board orientation, not schematic)
R20- Bottom leg has tone, not top
C 13 Bottom leg has tone not top
R21 both legs have tone
IC2B pin 6 no sound
C14 Top leg has tone, not bottom
R24 Top leg has tone, not bottom
R23 both legs have tone
IC2 pin 7- good tone

Does this tell us anything?

[Big mike 1100]

So I tested the board tonight with an audio probe-

It appears that per the schematic, there is no audio coming from everything that stems from IC3, namely:

D3
D4
LEDR
Z1
R29
R30
C17
C20
C21
C22
C19
C18

There is also no audio from the path starting with C16.  Namely:
C16
R19
R16
C12
R15
R17
R18

And IC2 has no audio from pin 2 or 6, but it's loud and clear in pin7

And what should I be hearing from IC3?  I ask because I'm hearing nothing on any pin, except a high pitch squeal on one of the pins (Just forgot which one). 

Could it just be another bad TC1044 IC in IC3 that's working but not working well enough, and maybe a bad C16?  There were several resistors that had audio, but were noticeably quieter than the others

[Slowpoke101]

The only noise that you would get from IC3 is a high pitched squeal. It is a DC/DC converter using charge pumps to generate the +18V and -9V rails. However you are getting audio in places that is a bit odd and no audio where it should be expected.

Does your audio probe have a capacitor in series with the probe?

[Big mike 1100]

It does have a capacitor- a .1uf I believe.  I set it up like as recommended like this video.

https://youtu.be/jWvIfDSxbIk

I was going to just start at C16 and either replace parts and test as I go or examine each more carefully.  Is there a better plan?

Where is the audio that shouldn't be there and vice versa?  I assumed that you should hear the audio at each point along the schematic.

[Slowpoke101]

A very quick way to set up an audio probe. Should work fine.

From your previous posts you are get a low level of audio on IC1 pin 5 and 7. It should be a far higher volume on pin 7. But your voltages are correct so your gain level must be somewhat low. Check all the components around IC1B and make certain that the gain pot does work as a pot. Test it with resistance test on your multimeter. I also note that you are using two separate pot for the gain...For your tests set both pots to mid-range and make sure that the connections are correct. Things get a bit funny when using two pots in place of a single dual pot - one of the pots has to be wired in reverse if you want to maintain the correct rotation control direction - eg, fully CW (clockwise) is maximum.

Have a look here; http://www.coda-effects.com/p/klon-centaur-circuit-analysis.html for a simple breakdown of the circuit's operation. It may help you to narrow in on the problem.

[Big mike 1100]

Thanks Slowpoke-that's a really helpful page- it looks like much of the problem could stem from the 100K gainB, as I can trace a line of bad components from that pot to all of the non-audible components:

R15-R17-R18-C12 and maybe R19 and C16, but I'm still learning how to read a schematic and the flow.


I'll start by disconnecting the two separate gain pots and putting the dual pot in place. 

Am I correct that there should be no audio in all of the components coming off if IC3, at the bottom right part of the schematic?

[aion]

Am I correct that there should be no audio in all of the components coming off if IC3, at the bottom right part of the schematic?

Correct, no audio on IC3 - its only function is to convert the 9V input voltage to +18V and -9V.

[Big mike 1100]

Well I replaced the two gain pots with the correct dual gain pot, mounted to the PCB board.  I also replaced C16, just for good measure (mounted the correct way).  I touched up the solder joints and looked for bridges.  Same results.

I think at this point, I'll take a break from it and look at other projects, unless there is another suggestion to try.

Thanks!

[DIY Bass]

I can't see any way that you could have audio on pin 7 IC2 without audio on Pin 2 and 6 of IC2.  I thhink that there must be a short somewhere there to earlier in the circuit.  What you want to do is follow through the circuit from one end to the other and see where the signal disappears.  Try these points first and let us know what you find. You can do this.

IC1 pin 3
IC1 pin 1
IC1 pin 5
We know it doesn't get to IC 2 pin 2, so I would check somewhere around R13 and R16 as well and just what audio you have there.

[Big mike 1100]

The IC2 pin7 audio (which is LOUD and Clearer than other parts of the board) confuses me as well.  I'll give it a shot and report back. 

It looks like there is more than one path in the circuit based on the link that Slowpoke provided me a few posts back- A bypass path and clean path and maybe two gain paths.  I'll try them all again.

Question 1-when I probe the path, there are some components that have audio on one leg but not the other- like R8 and R9, whose legs seem to go to VB.  Is this normal or are those components suspect?  There are others with that issue as well. Are they even part of the audio path or their leg is just in the way??

Question2- could it still be a bad IC3 at this point, or one of the other ICs for that matter?

Thanks for the advice!

[DIY Bass]

I haven't found anywhere the actual track layout for the board, so not much help here, but I would be suspicious of a short from the track connected to pin 7 IC2 to somewhere earlier in the signal chain.  I would be looking at anywhere you have 2 pads close together that should not actually be touching according to the schematic, and measure them with a multimeter to see whether there is any connection that shouldn't be there.

[Slowpoke101]

I do recommend that you try to clean the solder flux away on the solder side of the board. Methylated spirits, denatured alcohol or similar products can usually clear flux. An old toothbrush is very useful.

A picture that you posted a while ago showing the solder side of the board is of fairly low resolution and is a bit hard to see things. Additional magnification just makes the image worse but it has shown a few areas to check. In the following picture I have outlined the areas that may require attention. Some joints do not appear to be fully soldered or there is excess solder that may cause a short - IC1 pins 5 to 7 may have a problem.




See what you find.

Now, Vb is the 4.5V reference rail. It should not have any audio on it. So if a leg of a component is connected to Vb that leg will not have audio on it but the component's other leg may have audio on it (depending on where in the circuit it connects to).

IC3 is generating the correct voltages (from your measurements), so it is working and not to be worried about.

A high level of audio on pin 7 of IC2 is odd considering there is no audio on pin 6. I can't explain that yet but make sure that pins 5 and 6 of IC2 are not shorted together.

[Big mike 1100]

Thanks for the additional help!  I'll purchase some denatured alcohol and have at it tonight, in addition to your and DIY Bass's other suggestions.

[highwater]

IC2 is a pair of inverting stages. It's perfectly normal not to have audio at either input of an inverting stage... in fact, if there *were* signal there, it *would* be a problem.

The opamp's job is to drive the feedback such that both inputs have the same voltage... in the case of an inverting stage, the non-inverting input is held to a constant DC voltage, and the feedback connects to the inverting input.

[DIY Bass]

Looking at the schematic there should be audio on pins 2, 1, 6 and 7 of that IC.  If there is not then there is definitely a problem of the "It's busted and I can't hear anything at the output at all" kind.

[Big mike 1100]

Thanks again for all of the help.  I took all of the suggestions and here are the results.

I cleaned the board with Methylated spirits and here are the new pics of the back of the board.  The Yellow circles represent the pins/joints that are testing positive for continuity.  Not sure if they should or not.

****Edit*** I uploaded one picture with colored markings that show which pins are connected to each other by matching colored circles- The pics below all have separate circles- Just thought of it as soon as I hit "post" sorry.*****

Regarding what DIY Bass said- I traced IC1 Pins 3-1-5 and While Pin 3 and 5 showed normal clear volume, Pin 5's volume was clearly quieter and more trebly.  He also mentioned testing R13 which had the same quieter, trebly sound as pin 5 of IC1.

Regarding R16- the pin on the right (facing the front of the PCB) had the same quiet/trebly sound, but the left pin had no audio.

Slowpoke said "A high level of audio on pin 7 of IC2 is odd considering there is no audio on pin 6. I can't explain that yet but make sure that pins 5 and 6 of IC2 are not shorted together."  I checked and they are not, but the pics with the yellow circles show which pins test positive for continuity.

I'm not sure if I should be testing anything additional based on the last comments from DIY Bass and Highwater.  I haven't desoldered anything at this stage, as I've touched the joints up several times and don't want to create the possibility of additional bridges unless you guys say so.

[Aph]

Once again, kind of fuzzy and hard to really see... but on your first photo, just below the two yellow circles, it looks like a possible solder bridge. Looking at the top of the board, this would be a short between R13 and C3 (I think).
And another possible bridge about three pads to the left of the left yellow circle...