Aion Quantum Build Problems

[rmsmarr]

Hello I'm building the Aion Quantum new 125b board.  I've finished and tested  and everything works fine, beautiful distortion  nice tone controls but no gain on the level pot. I checked and double checked parts installed.

My op amp readings(I tried several) are  pins:     1)  4.55                5) 5.45
                                                                         2) 4.55               7) 4.56
                                                                         3)  4.14              6) 4.56
                                                                         4) 0                    8)  9.13

Q1                   C  9.13
                       B  5.14
                       E  5.03

Q2                   C   9.13
                       B   4.36
                       E   4.33

Any help appreciated

[idy]

No gain meaning nothing above unity? No change in volume?

Probably bad solder on level pot. One leg looks dodgy.

If it sounds good the problem is unlikely anywhere else.

[patrick398]

Pin 5 should be sitting at half supply with the other pins. Yours is at 9v so that would be my first concern

[Kipper4]

I think he's made a mistake there Pat.
If pin 5 where at +rail then you'd expect 6,7 to also be at +rail no?
Just trying to help.
We all want you to fix it.
Is it a screamer type ting ?

[rmsmarr]

I made a mistake on the voltage of Pin 5 on the op amp  it's 5.45 v  I corrected it.  I also reflowed solder on level pot. And still the same problem.

When I say no gain I mean volume of  the distortion is lower than the dry signal.

[Kipper4]

Have you an audio probe?

[patrick398]

I think he's made a mistake there Pat.
If pin 5 where at +rail then you'd expect 6,7 to also be at +rail no?

Good point

When I say no gain I mean volume of  the distortion is lower than the dry signal.

Did you test the board before you boxed it? Does the problem persist with the circuit outside of the enclosure?

[rmsmarr]

I did not Rock before I boxed.   I have an audio probe and will run a signal thru it and try to find the problem today.

Thanks

[rmsmarr]

Ok I've unboxed the circuit  and tested it with the audio probe.  There still seems to be no hard drive in the output stage.  The signal is really strong into the level pot but comes out weaker than the input signal.  The pot checks out properly on the ohm meter at 100k. Could one of the caps be suspect in the output stage?   There is just no drive to the distortion

[idy]

Is pin 1 of the volume pot reading voltage B? Is there some short/path to ground from pin 2? You might try lifting out one leg of c13 to determine if the problem is before or after it.

[DanZ]

Hey, I hate to bump an old thread but seems silly to start a new one.

I just finished up a Quantum too and I'm having the same problem. Did you manage to solve yours?

[iainpunk]

welcome to the forum.

do you have an audio probe?
they are tremendously handy in following the signal to the point where its not being handled properly anymore.
furthermore, try the debug guide

cheers

[DanZ]

Yup. Everything is fine until I hit pin 2 on the level pot and that's where the volume just drops off. Even swapped it out with the same results.

I'm getting the same higher than usual voltage on the B and E legs of Q1, 6.61 and 6.04. And pin 3 on the IC is reading a little lower, 4.3 instead of 4.6 I think.

Checked all my solders and R values, all look good.

[MikeA]

What transistor are you using for Q2?  The PCB has two overlapping sets of holes to accommodate both E-C-B and E-B-C pinouts.   If the transistor pinout and the holes are mismatched, you'll have trouble that looks a lot like this.  Briefly:
2N5088 = EBC = use the rightmost 3 holes, flat side of the transistor toward the north (matches the PCB silkscreen)
2SC1815 = ECB = use the leftmost 3 holes, flat side of the transistor toward the south (opposite from the silkscreen)

[rmsmarr]

Hey, I hate to bump an old thread but seems silly to start a new one.

I just finished up a Quantum too and I'm having the same problem. Did you manage to solve yours?

I did not.  It's just sitting collecting dust on my bench.  Keep me posted if you solve the problem.  I kind of lost interest. 

[DanZ]

What transistor are you using for Q2?  The PCB has two overlapping sets of holes to accommodate both E-C-B and E-B-C pinouts.   If the transistor pinout and the holes are mismatched, you'll have trouble that looks a lot like this.  Briefly:
2N5088 = EBC = use the rightmost 3 holes, flat side of the transistor toward the north (matches the PCB silkscreen)
2SC1815 = ECB = use the leftmost 3 holes, flat side of the transistor toward the south (opposite from the silkscreen)

I'm using 5088's. I'll have to look at that when I have some free time.

I'll report back when I do.

Thanks!

[DanZ]

No luck. Wasn't the 5088s.

I'm running out of ideas. Tore apart the power section. Nothing. Only thing I could think of is I have a bad part somewhere.

[idy]

The answer is almost never "bad part." Much more common, error, bad solder joint. Much much... except wrong part value, like R15 being something other than 510k...

If all the opamps and everything are working, and the volume dies at the level control, why tear apart the power supply?

Confirm that there is 4.5 v on pin 1 of level control.

If the signal dies there at the pot, little chance that the following transistor is the culprit. You could pull pin2 of the pot out of the pcb to confirm that removing the final buffer does not restore the volume of your sound.

Reflow parts near the pot (in the schematic) like c13.

we don't have all your voltages do we? It looks like the opamps and transistors are biased at 4.5, except Q1 should be at around 6v (9.1k/22k). Someone know why the buffer is biased like that? I can't see how that last transistor Q2 could be 6v and not 4.5.
It is normal for pin 3 and 5 (the + inputs) to read a bit low, that's called "loading" from the meter.

[PRR]

Going on 3 years and 18 messages, and still no schematic in thread?

[DanZ]

Ok. It's been a while, I know. Time can get away from you when you own a business.

So I checked all the voltages on Q1 & 2 and the IC and are as follows (the ideal voltages are in () )

Q1
E 6.04 (3.68)
B 6.67 (4.10)
C 9.47 (9.44)

Q2
E 4.10 (3.74)
B 4.72 (4.15)
C 9.46 (9.44)

IC
1 4.73
2 4.73
3 4.3 (4.6)
4 0
5 4.62
6 4.72
7 4.72
8 9.44

I refuse to start a new pedal until I figure this one out. I think I mentioned in the original post, there's no volume until the last 1/4 turn or less on the volume and distortion. And the volume drops like a rock if you turn either past a 1/4 turn down.