Aion Electronics Stratus OD - no gain, no volume boost

[suryabeep]

Hi everyone,
I built an Aion electronics Stratus project  (https://aionelectronics.com/project/stratus-ibanez-ts9-od808-tube-screamer/) to Fulltone RTO specs. When I switch it on, there is no drive at all, and a *very* slight volume drop with all the knobs maxed out. I'm using an LF353N ic and the mids and bass mods. Here is the measured voltages at the IC pins:
pin1: 4.34
pin2:4.34
pin3: 4.34
pin4: 0
pin5: 3.65
pin6: 4.53
pin7: 4.30
pin8: 9.59
This is the first time i'm using a multimeter, so I may be doing the whole process wrong (I'm a total noob at debugging). What could be the problem?

[robthequiet]

The first thing I would check here is the foot-switch. Your voltages look good.

Power off, then use meter on ohms to check for continuity from the tip of the input cable to the place on the circuit board where the signal enters the circuit. It should show zero ohms or some way higher ohms,  depending on whether the switch is on or off. If it never shows zero ohms, then trace the wires back to the switch to make sure they are connected to the right lugs.

If you have a way of posting photos of your build so that we can see the wiring and components that would be a great help. Especially a close photo of the switch.

PS Welcome aboard!

[suryabeep]

I checked the footswitch, the meter reads 0 ohms when the footswitch is on.

[EBK]

That's a lot of paint inside the box....  Do you have ground continuity to that jack with only one wire?

[suryabeep]

Yeah, it seems like all the grounding points have continuity. The paint shouldn't be an issue, I have built many Aion projects in enclosures similar to this and there hasn't been a problem so far.

[EBK]

Could you measure your Q2 voltages?
Also, do you get a reasonable signal at the base of Q2?

[suryabeep]

this is what I got for q2: EBC: 3.58, 3.98, 9.59

[suryabeep]

Some more details that may help find the problem : the tone knob doesn't produce any change except for when it is maxed. Then it creates some high pitched oscillation (I think that's the sound). The volume knob works properly. The drive knob doesn't do anything.


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[EBK]

this is what I got for q2: EBC: 3.58, 3.98, 9.59

I would expect about a 0.7V difference between the base and emitter.  You are getting 0.4V.

[suryabeep]

Could this be because of a bad transistor?

this is what I got for q2: EBC: 3.58, 3.98, 9.59

I would expect about a 0.7V difference between the base and emitter.  You are getting 0.4V.

,

[EBK]

Any chance that the board is shorting out on the back of one or more of the pots?

[suryabeep]

Any chance that the board is shorting out on the back of one or more of the pots?

Nope, I used electrical tape to cover the back of the pots.


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[EBK]

Yeah, it seems like all the grounding points have continuity. The paint shouldn't be an issue, I have built many Aion projects in enclosures similar to this and there hasn't been a problem so far.

Sorry to go back to this, but did you specifically measure between the output jack sleeve and ground?  I understand that you've been lucky in the past, but I hope you didn't skip this test....

[suryabeep]

Yeah, it seems like all the grounding points have continuity. The paint shouldn't be an issue, I have built many Aion projects in enclosures similar to this and there hasn't been a problem so far.

Sorry to go back to this, but did you specifically measure between the output jack sleeve and ground?  I understand that you've been lucky in the past, but I hope you didn't skip this test....

The output jack sleeve isn't grounded. All ground points in the pedal (9v power jack, input jack, switch, and the board) are grounded to the input jack sleeve.

[EBK]

The output jack sleeve needs to be grounded, either via a wire or through electrical contact with the metal enclosure (which is grounded through the input jack).  Your wiring assumes the latter, but the paint may be getting in the way. Problem could instead be at the input jack (same reason), but we would probably expect more noise if the enclosure is not grounded.

[suryabeep]

The output jack sleeve needs to be grounded, either via a wire or through electrical contact with the metal enclosure (which is grounded through the input jack).  Your wiring assumes the latter, but the paint may be getting in the way. Problem could instead be at the input jack (same reason), but we would probably expect more noise if the enclosure is not grounded.

I see. I'll sand the paint off of the area of contact inside the enclosure then.

[robthequiet]

The drive knob doesn't do anything.

Makes me curious if the drive knob section is open somewhere. Do you get a change in resistance between one of the outside pins and the wiper if you turn the knob?

[robthequiet]

By the way, is R2 missing on the PCB?

Nevermind, it looks like you've bypassed the input buffer. Sorry i didn't pick up on that.

[suryabeep]

I remeasured the IC voltages :
Pin1,2,3,6,7- 4.80
Pin4- 0
Pin5-3.86
Pin8- 9.58

I measured resistance between the drive lugs as well:
Anti Clockwise - 0 ohms between 2 and 3 as well as 2 and 1.     I think this is the problem?
clockwise - 0 ohms between 2 and 3, 1 between 2 and 1.

Yes, R2 is omitted in this variant.


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[robthequiet]

Ah yes, missed your reply. So you've bypassed the input buffer.

If there is no resistance offered by the drive pot, it will not induce gain in the op amp. Probably good idea to check the wiring.