SOLVED Uberdrive - no sound

[Grubb]

Hi folks, my mate posted me his Uberdrive build that is not producing any sound. Apart from flux on the board - which I've carefully cleaned, avoiding the pots - I can't see too much wrong with it. I pulled it out of the enclosure and sat it on the Auditorium and it's still not making a sound. LED comes on, bypass was working in the enclosure. He's used 2N3904 transistors in place of the 2SC732s called in the BOM, is that ok? I checked the pinout and believe they need to be flipped around, hence looking like they're in backwards in the photos. Can anyone spot anything? What should I check next?

 

[giovanni]

I don’t see anything obviously wrong. Did you check all component values? After that, it may be time to measure some voltages on transistors and IC.

 

[temol]

2SC732 - ECB
2N3904 - EBC

 

[music6000]

This had the same issue:

SOLVED - uberdrive. no signal when switched on. made an audio probe. need some tips

first pedal build attempt. after successfully building a couple tube amps (incl. jcm800 50w / 2204 clone) i thought i’d have a go at pedals, starting with the uberdrive. i hooked it up exactly as specified in the build docs. only deviations were: couldn’t get hold of the specified 2SC732, so i...

forum.pedalpcb.com

 

[Grubb]

I rigged the 2N3904s as in the thread above but no joy.

Here are some measurements. I don't know enough yet to know what they mean.

IC1
P1: 8.49V
P2: 7.79V
P3: 7.73V
P4: 0V
P5: 8.49V
P6: 8.52V
P7: 8.5V
P8: 9.06V

D1
A: 8.16V
K: 7.81V

D2
A: 7.81V
K: 8.51V

D3
A: 8.51V
K: 7.81V

Q1
E: 3.59V
C: 9V
B: 4.03V

Q2
E: 2.99V
C: 9.07V
B: 3.36V

Happy to measure again if some of that is clearly wrong, this is only the second time I've measured voltages. Cheers.

 

[Grubb]

R1 appears to be 2.2R rather than 2.2M, I'm checking other component values as I go. Could that give the behaviour we're seeing?

 

[Grubb]

Replaced R1 with 2.2M but still not working. All other component values are correct. What do I check now?

 

[JamieJ]

Sounds like audio probe time.

 

[finebyfine]

Looking over it I’m at a loss too. If you hadn’t already measured the socketed components I would have said it might be the sockets. You might have to bite the bullet and trace the circuit all the way through as annoying as it is to do

 

[Grubb]

I don't have a probe yet, can checking continuity help at all? Otherwise I'll have to wait until I can get one.

 

[finebyfine]

I don't have a probe yet, can checking continuity help at all? Otherwise I'll have to wait until I can get one.

Yep, that’s actually what I meant. I have an audio probe but for some reason using a dmm’s continuity function always feels like the easier way

 

[JamieJ]

I don't have a probe yet, can checking continuity help at all? Otherwise I'll have to wait until I can get one.

Do you have a spare 100n box cap?

it’s fairly simple - https://www.diypedalgearparts.com/en/novita/26_Audio-probe-how-to-build

or you can use the continuity method of you prefer.

 

[finebyfine]

Here’s a gutshot of my working build on the off chance it helps at all also but I think we all agree nothing looks off visually on yours. I used 2n5089s I think

 

[Grubb]

Do you have a spare 100n box cap?

I certainly do, didn't realise I could just slap one together!

The terminals are a cool idea on that build @finebyfine

 

[Mcknib]

Your op amp voltages are off input and output pins 1,2,3,5,6,7 should be half power if it's 9v around 4.5v

You've got power and ground pins 4 and 8 as it should be, check what voltage you get on the empty socket pin 3

 

[music6000]

Your op amp voltages are off input and output pins 1,2,3,5,6,7 should be half power if it's 9v around 4.5v

You've got power and ground pins 4 and 8 as it should be, check what voltage you get on the empty socket pin 3

Agreed, Do you have a spare dual opamp you can try that you know that works ie TL072, OPA 2134
I don't like the look of that ? JRC4558.

 

[Mcknib]

Agreed with @music6000 looking again at your voltages Q1 base is getting VREF so I'd expect VREF at pin 3 of IC1

Meaning yer op amps probably kaputt

 

[Grubb]

Solved - dead 4558. I double-checked the voltages again and confirmed they were mostly too high. I swapped in a 4558 from my Nobleman and took voltages, all roughly around 4.5V apart from 0V and 9V on their respective pins. So I plugged it in and we have life and glorious sound. I'm sending it back to my mate without a chip and he can do the honours and fire it up. Thanks for your help everyone!