Debugging:Aion FX Graviton:no sound/no distorsion

[Petersson]

Ey up.
Aaaallmost no sound. And no distorsion.



Build doc:

https://aionfx.com/app/files/docs/graviton_documentation.pdf



Voltages should be =left column.
Voltages is=right column.

Changes from original: C19 is mlcc not film. (Was out of film caps)
Q3 is jcn 3906 (unable to source2n5087)


sound probe result:  i've got signal on one side of r6. I've got signal of one side of c3. No signal either side on r7.  No signal c6. Q2 is signal on E and B.  Any clues? 😕

(No signal can still be a signal but veeery low. Way lower than measuren on q2)

[eh la bas ma]

Hello, and welcome.

I think there are some suspicious solder joints on your build, and some spots with probable shorts. I circled what I could see in red.


You can find 5087 here : https://www.musikding.de/2N5087_1 (hoping you are in europe)

Edit : " i’ve got signal on one side of r6. I’ve got signal of one side of c3. No signal either side on r7.  No signal c6. Q2 is signal on E and B.  Any clues? "

I am not sure if R7 is in the signal path, can you check R9 and R10 ?
If the signal is lost in this area, first thing is to reflow all pads in the aera. Just take every heat-sensitive socketed parts (transistors and IC) off the board, and apply some heat on all pads untill the solder gets liquid. Then, spread it evenly on the pad. Don't apply heat on a pad more than 4 - 5 seconds, you don't want to overheat and burn the board.

You can also begin with continuity tests in the aera where the signal stops, following the schematics, to know precisely which pads you need to reflow, instead of reflowing everything.

Continuity test, with your multimeter, between two components will tell you if the soldering is ok or not.

Edit 2 : Here is a useful picture shared by Bluebunny in another debugging thread :



Edit 3 :

I understand that Aion's Q3, the 5087 (Hfe 250-800) that you subbed with 3906 (Hfe 60-300), is Q7 in the original HM2 schematics.

From this thread : https://www.diystompboxes.com/smfforum/index.php?topic=114410.0

I understand Q7 is "extra gain", so a 3906 (with a lower gain than 5087) can maybe do a noticeable difference in the sound, but I am not really sure about that.

See reply #1 : "I wouldn't recommend changing Q7, R49, C31 unless you think it has too much gain and want to tame it a little bit."