Help debugging JHS Morning Glory Clone

[OasisMcFly]

Hi All,

I am at my wits end with a JHS Morning Glory clone made using the layout from Guitar FX Layouts as seen here:

http://tagboardeffects.blogspot.com/2013/05/jhs-morning-glory.html

The pedal worked great for over a year, but last week started randomly dropping all signal. At first, I could unplug and replug the power and it fixed it, but now it dies after about 2 secs. If I give it a signal while I power it on, I get souud for 2 seconds and then nothing.  I set about my usual fault finding methods, but I haven't been able to figure out what was wrong. Rather than spend forever diagnosing it, I decided to just populate a second board, drop it in the enclosure and call it a night. The second board has the exact same issue.

So far here is everything I have done:
- checked both boards for cold solder joints
- checked for unwanted solder bridges
- I triple checked all the components to make sure they had the right values and were placed in the right holes on the board.
- I checked the IC and Transistor for the correct orientation.
- replaced the power jack
- I checked the pedal with a known good power supply
- Checked all the pots with a multimeter and verified that they are the correct value and sweep
- checked all the cabling for continuity to make sure there wasn't a break in a cable somewhere
- Checked for continuity at all the grounding points

I feel kinda mentally exhausted by this now, and I could definitely use some extra input on what to check for.

For reference, here are the values I get when I measure voltage on the IC

1.  1.49
2.  1.49
3.  0.5
4.   0
5.  0.87
6.  3.09
7.  3.62
8.  8.52

I'm basically a beginner with this stuff, but these values seem wrong to me. I don't know what else to check for, or what I might be doing wrong. Can anyone help?

[EBK]

Have you tried replacing the stomp switch?

[OasisMcFly]

Not yet. I've got plenty of extras, so it wouldn't be a big deal to swap it out. I'll do that as soon as I get home tonight.

Out of curiosity, how could the stomp switch cause that?

[thermionix]

Maybe some meter loading on those voltages, but some pins are way off.  Maybe a failing electro?  Got a schematic?

[OasisMcFly]

I believe the schematic used can be found here:

http://guitar-fx-layouts.42897.x6.nabble.com/file/n3657/Morning_Glory.jpg

[EBK]

Not yet. I've got plenty of extras, so it wouldn't be a big deal to swap it out. I'll do that as soon as I get home tonight.

Out of curiosity, how could the stomp switch cause that?

I was led there by the fact that it did previously work, but now doesn't, and a newly populated board dropped into the same place has the same problem.  This tells me the problem is outside of the board.  Switches are prone to mechanical wear, and since you likely resoldered the jacks and pots with the new board, and you checked the pots....   Well, I'm left with the stomp switch at this moment.

[duck_arse]

have you used any tantalum caps in either build?

[OasisMcFly]

So I replaced the footswitch and the input/output jacks. No change. I rechecked the board for solder bridges, and didn't find any.  I found some instructions on how to make an audio probe, so last night I made one to help troubleshoot this. However, I am still really new at this, and I am not sure how to follow the signal through the circuit on the Vero layout. I probed around, and found several spots where the signal was nice and clear, but I don't really understand how to determine the path I should be checking.

There are two different tantalum caps I used, C7 and C10. 47pf and 470 pf respectively. Last night I replaced them both for good measure.

[thermionix]

47pF and 470pF are probably ceramic, not tantalum.

[OasisMcFly]

Geez, I completely got that wrong. I think in my mind I've been referring to the ceramics as Tantalums, and the tantalums as ceramics. With that being the case, then no there are no tantalums in this build. Just the two ceramics, the electros, and the box style caps.

[OasisMcFly]

So the audio probe was amazing. Admittedly, I'm still not sure of the proper way to follow the signal through the chain. I think I understand most of it, but there is still a lot of confusion for me there.

Even so, probing around, I found that I had no signal past drive 3. I replaced the 100n cap that follows it, and the pedal lives again! For reference, this was in the second board I made. At this point, I'm just happy it works, and at a later date, I will try to diagnose the first board as well.

Thanks for all the help!