TS808 pops when LED in, all other TS808’s fine?

[Kroars]

So, I’ve been scouring for the last couple days, read the AMZ article and combed through the forums. Found a lot of helpful tips and suggestions for solving this. My question is, what could cause switch pop when LED is engaged in a particular TS (the LGSM pcb) build, when all others have been fine?

I’ve replaced the electrolytic caps, testing prior to installation. All Nichicon from Mouser, aside from the 10uF output cap I used a Tantalum as an additional measure. I’ve replaced the foot switch with another Pro 3pdt from SBP. Reflowed all solder joints using a flux pen just to be sure. Still the problem persists.

Only pops when indicator LED is in the circuit. I could certainly add a cap and resistor as AMZ suggests. I’m just curious as to why that would happen in one build when the others work perfectly?

I haven’t replaced any of the film caps, but they’re all Wima MKS2’s from Mouser.

I can add photos later this evening. I was hoping someone could shed light as to how this happens with the indicator LED in particular.

Thanks!

 

[Cybercow]

It depends on what the actual circuit/schematic reveals.

 

[JTEX]

As a troubleshooting step, I'd try removing this wire first and see if it still does it.
(the wire grounds the input of the board when the effect is bypassed).

 

[chris.knudson]

Don't know if this will help or not. http://www.muzique.com/lab/led.htm

Apparently LED popping is common enough for there to be an article about how to solve it.

EDIT: Sorry, I just realized that apparently you have already seen this article.

 

[chris.knudson]

I’m just curious as to why that would happen in one build when the others work perfectly?

Have you tried a different LED? This one might be just causing a bigger voltage spike than your others.

 

[Kroars]

Don't know if this will help or not. http://www.muzique.com/lab/led.htm

Apparently LED popping is common enough for there to be an article about how to solve it.

EDIT: Sorry, I just realized that apparently you have already seen this article.

No worries. I certainly appreciate the help! I did try another LED, just in case. Same thing. I feel like I’ve tried everything. The weird thing is that I’ve built the same pcb, maybe a dozen times. Using the same batch of components from Mouser (resistors from Tayda), without an issue.

It’s nice to have the quick fix idea from Orman. I just want to know why this would happen. I believe I’ve eliminated leaky polarized caps, bad solder joints and footswitch. Perhaps a leaky Wima film cap?

 

[Kroars]

It depends on what the actual circuit/schematic reveals.

It’s the Little Green Scream Machine. I’m sure hundreds of these have been built without popping, I can claim a handful of them. I just haven’t found an explanation as to why it will pop when an LED is in on one build and not the others. I believe I’ve eliminated cold solder joints, leaky polarized caps and the footswitch (all were quality to begin with, but replaced/resoldered as process of elimination), problem still persists while indicator LED is connected.

 

[Kroars]

As a troubleshooting step, I'd try removing this wire first and see if it still does it.
(the wire grounds the input of the board when the effect is bypassed).

I’ll give that a shot!

 

[Kroars]

Here’s another stumper. I have one more pcb doing the same thing, this time a Skeptical Buffer. Again, I’ve built a few of these with no issues at all. Started off doing the same troubleshooting as above. I ended up getting so frustrated tonight, that I took my time replacing every single component (one at a time) on the pcb. This includes the three toggles, jacks wiring; everything. Cleaning the pcb with 99% alcohol as I went. I even replaced my irons tip. Used a flux pen on every one of the new solder joints. One by one, everything was replaced and each time the pop remained.

I just want to know how this could happen? The highest ESR reading for caps was 0.50 ohms.

Two pcbs, same issue; led pops. Hundreds built without any popping whatsoever. I get that I could probably solve the issue with Orman’s method. I’d rather understand why it happens if it doesn’t appear (keyword being appear) to be component/solder joint related. I’ve got replacement pcbs for each and lm certainly happy that the 99% built go without issue, but this LED pop is making me just a tad bit nutty (or nuttier….).

 

[chris.knudson]

Are you using a new batch of LEDs? Did you buy a new batch of parts. This seems odd that you've been building these without issue and now you have two giving you problems. I feel like some good detective work might be just as beneficial as some good troubleshooting here.

 

[Kroars]

Are you using a new batch of LEDs? Did you buy a new batch of parts. This seems odd that you've been building these without issue and now you have two giving you problems. I feel like some good detective work might be just as beneficial as some good troubleshooting here.

That’s the weird thing. Both were built within a week or two of each other. Roughly same batch of all components. I typically purchase large orders at a time. Maybe a dozen other pedals built between the two with no issues whatsoever. Also, it may be worth it to point out that I typically build two of the same pedal at a time. In both cases the other one had no issue. Very, very strange.

 

[chris.knudson]

That’s the weird thing. Both were built within a week or two of each other. Roughly same batch of all components. I typically purchase large orders at a time. Maybe a dozen other pedals built between the two with no issues whatsoever. Also, it may be worth it to point out that I typically build two of the same pedal at a time. In both cases the other one had no issue. Very, very strange.

Yeah, this one feels like a head scratcher. I just built a Mean Green Metal Machine a few weeks ago, and I didn't have any LED pop issues with it. Have you (and sorry if you mentioned this before) reflowed your solder joints. LED pop is caused by a voltage surge that is amplified by the high gain circuit. A cold solder joint could potentially cause a voltage surge. Also, is there anything in the grounding of the circuit that might be suspect -- that can also cause a voltage spike. At this point I'm just throwing darts in the dark.

 

[Kroars]

Yeah, this one feels like a head scratcher. I just built a Mean Green Metal Machine a few weeks ago, and I didn't have any LED pop issues with it. Have you (and sorry if you mentioned this before) reflowed your solder joints. LED pop is caused by a voltage surge that is amplified by the high gain circuit. A cold solder joint could potentially cause a voltage surge. Also, is there anything in the grounding of the circuit that might be suspect -- that can also cause a voltage spike. At this point I'm just throwing darts in the dark.

Yup, reflowed everything. Even using a flux pen, just in case. After rebuilding the SB one component at a time, I think I’m going to put both pcbs in a box for a while. Maybe come back to them at a later date. I wonder if a damaged trace could cause switch pop -but only when the LED indicator is present. I’m not sure that would explain the initial problem, unless there was a thin trace or something. I’ve never had an issue that was due to a PPCB board and I’ve probably built over half his catalog. Although, anything is possible. I’m sure it was something I did, or a component somehow.

As mentioned previously, I didn’t have any cap over 0.50 ohms ESR. Would that be enough to cause it? That’s another thing I haven’t come across yet, at what level ESR & vloss is suspect when measuring capacitors? I’ve seen the question posed in a couple threads here, but not answered.

 

[music6000]

Yup, reflowed everything. Even using a flux pen, just in case. After rebuilding the SB one component at a time, I think I’m going to put both pcbs in a box for a while. Maybe come back to them at a later date. I wonder if a damaged trace could cause switch pop -but only when the LED indicator is present. I’m not sure that would explain the initial problem, unless there was a thin trace or something. I’ve never had an issue that was due to a PPCB board and I’ve probably built over half his catalog. Although, anything is possible. I’m sure it was something I did, or a component somehow.

As mentioned previously, I didn’t have any cap over 0.50 ohms ESR. Would that be enough to cause it? That’s another thing I haven’t come across yet, at what level ESR & vloss is suspect when measuring capacitors? I’ve seen the question posed in a couple threads here, but not answered.

Have you tried reseating the Op Amps in your builds?
Are you using Machined Dip 8 Sockets or the less desirable in my book Leaf spring type.

 

[chris.knudson]

at what level ESR & vloss is suspect when measuring capacitors?

I don't know the answer to that question. Maybe somebody does and can chime in?

 

[Kroars]

Have you tried reseating the Op Amps in your builds?
Are you using Machined Dip 8 Sockets or the less desirable in my book Leaf spring type.

While I am using the less desirable leaf spring variety, I did replace both the opamp and charge pump as well as the sockets to no avail. I replaced everything on the pcb one by one, after replacing the usual suspects. I went a little crazy on this one…..

 

[music6000]

You definately got the listed 10K at R15, The pulldown resistor at the end as that is a known problem on plenty of circuits with 100K ???
10K - Brown, Black, Black, Red, Brown.

 

[jimilee]

Have you tried a different amp?

 

[Kroars]

You definately got the listed 10K at R15, The pulldown resistor at the end as that is a known problem on plenty of circuits with 100K ???
10K - Brown, Black, Black, Red, Brown.

Ya know, that’s one thing I didn’t check on the TS808. You could be right on that one. My eye sight is certainly not what it once was. The Skeptical Buffer is the one that I removed all components and reinstalled. I’ll report back tonight. Thank you!

 

[Kroars]

Have you tried a different amp?

Nope, just my Rockerverb. I could try the TH30, I suppose. I’ve tried it through my RV with other TS808’s without issue.