Aion Cerulean Build (Bluesbreaker / Morning Glory)

[Ajbraft]

New to building...started during this quarantine.  This portal seems to have a lot of helpful kind folks...good change of pace from the rest of social media.  Into my 8th build and second from Aion and this one has me puzzled.  It's a full kit from Aion for the Bulesbreaker with the Morning Glory JFET stage at the end...no additional mods.  Build went fine but when I fired it up it was all functional however, the volume was considerably lower then bypass.  Diode switching would bring it down lower as I would expect.   Since signal is getting through I thought I'd start at the power stage and I'm finding some wacky voltages and maybe someone can school (advise) me on some of this.  Thanks in advance!

The power section looks to have the polarity diode, filtering and a voltage divider so that 9v and 4.5v can be used several places in the circuit.  What I'm seeing is that the voltage divided is only 0.37V. 


I can't figure it out.  I take an ohm meter to every resistor prior to install.  What is strange is that when power is on the circuit, my ohm meter doesn't read anything on R9/R10 (or like it's maxed out).  When I take power away (with the resistors still in the board), they both read only 21k resistance.  When I take them out of the board and check them they show 47K as expected. I'm new so can DC or Caps impact you testing the resistance across the resistor?  Would you just place 2 new resistors in and see what happens?

Some of the results (voltages) are:

IC TL072P
1- 4.44
2- 0.07
3 - 0.37
4- G
5- 0.02
6- 0.47
7- 4.43
8- 8.9

Q1 2N5457
1- 0.5
2- 0.5
3- 0

[willienillie]

Can you post the whole schematic, and maybe pictures of your build?

[PRR]

> when power is on the circuit, my ohm meter doesn't read anything on R9/R10 (or like it's maxed out).

You can NOT normally read Ohms when power is in the circuit. (An ohm meter works by injecting a known power and seeing what happens; normal circuit power overwhelms the meter's test-power.)

> resistors still in the board), they both read only 21k resistance.

There is a loop from V+ through these two resistors and _back_ to V+ through those capacitors and surely other parts cropped out of your image. So when you test "one" resistor you really see both resistors in parallel. Should be 23.5k; "21k" could be other leakage paths *again* not shown in your sniplet.

> Would you just place 2 new resistors in and see what happens?

It is quite unlikely the 47Ks are broken. It is mildly possible you grabbed a 47K and a 47r, or some other wrong value. But the more likely possibility is some heavy load on "VR", again off-image.

[PRR]

https://aionelectronics.com/project/cerulean-bluesbreaker-overdrive/


AFAICT, the "VR" at VOL pin 1 is a typo?

[MikeA]

For the Morning Glory version of this build, you have to tie lug 1 of the Volume pot to ground instead of VR.  Did you bend that leg of the pot and insert it in the second hole (ground) provided in the PCB to the right of C11?

[Ajbraft]

Thanks!

No I just put VOL in the PCB.  I will confirm if the PCB is wired to V or G.

[Ajbraft]

Just checked VOL.  Lug 1 is going to ground via PCB.

I cleaned up the PCB (residue) and hit several solder points again but no change.  I did take the sub boards out and re-seated the ribbon wires to the headers and checked the voltages again.
I don't know exactly what the voltages should be but they look better to me.  Some sort of loop as suggested.  Tried it again but the volume is still very low.  Adjusting the presence and tone increase volume but only the brittle tones of course. 

IC TL072P
1- 4.45
2- 4.45
3- 4.45
4- G
5- 4.45
6- 4.45
7- 4.45
8- 8.9

Q1 2N5457
1- 4.45
2- 4.0
3- 0

[MikeA]

I just noticed the kit version PCB/schematic are a little different than the stand-alone PCB, I was looking at the stand-alone version (the same one PRR notated.)  There's no VB option on the Volume pot on the kit version so my comment wasn't helpful, sorry. 

I notice the readings on your op amp changed, you have VR on pin 3 now, and VR on Q1, so something you did helped.

[PRR]

> Q1 2N5457
> 1- 4.45  (D)
> 2- 4.0  (S)

Drain and Source are jammed together. Be *sure* Source actually connects to Rx4. Try another JFET.

[Ajbraft]

Thanks PRR,
Looking at the PCB and pin out of 2N5457 I see and verify that Source is going to RX6/RX5.  Drain to RX4. Gate to RX2/RX3.

Am I labeling this correctly?

I've attached a pic of the JFET section and my tracing.

[Ajbraft]

Thanks Mike.  I had to recheck the schematic to be sure.  I didn't see the VR on the volume until you mentioned it.  Looks like they fixed that issue some time ago.  Yes it seems I have some looping issues going on.  The voltages look good now on the OPAMP.  Now looking at the JFET.