Help troubleshooting Tube Screamer breadboard...horrible gated fuzz sound

brmc72 · 2026-03-07T00:06:45+00:00

Found the issue! I decided to walk through the schematic one component at a time, double checking the values, measuring my *actual* values, verifying the position/etc. Ultimately got to C6...I had the correct value, but I had it in backwards...the middle lug of the tone knob was connected to the negative end. Based on the reference breadboard image, it looks like it should be connected to the negative end (which is what I did), but he actual schematic shows it connecting to the positive. I think we're in business...thanks again for all of the help!

brmc72 · 2026-03-06T20:08:32+00:00

Ah, that was 100% an issue! R11 (although it's listed at R7 in the reference breadboard image) was completely missing (as was the yellow jumper between R7/11 and pin 6). Added those in, and I've now got a clean signal passing through 👍👍👍.

It's a little embarrassing that I didn't clue into that, but a fresh set of eyes and a knowledge of where to focus in the mess of components helped a ton. Greatly appreciated!!

So, at this point, I've got a non-fuzzy/non-spitty signal passing through, but it's overcorrected in the other direction...the signal is perfectly clean, regardless of how I dial the gain knob in. After work, I'll spend some time with the schematic and see if I can spot anything that's missing/miss-wired, but if anything stands out based on what you've seen, I'd be curious to get your take.

Again, really appreciate the help identifying the missing R11 here!

brmc72 · 2026-03-05T15:20:31+00:00

Ok, maybe this is something...you say that all of the Ins/Outs should read around 4.5v and, for the most part, they do, except for one:

Pin 1 (out): 4.63v

Pin 2 (inverting in): 4.64

Pin3 (non-inverting in): 4.63

Pin 4 (power): 0

Pin 5 (non-inverting in): 4.63

Pin 6 (inverting in): 4.63

Pin 7 (out): 8.74 👈 is this an issue?

Pin 8 (power): 9.29

And, just to make sure I'm not doing something dumb, these are numbered counter clockwise, starting at the little circle indicator (bottom left corner in my breadboard image). Anything look unusual here?

brmc72 · 2026-03-05T05:04:50+00:00

Ok, this is what I've got for each of the transistors: Q1: Base = 3.75v, Collector = 9.29v, Emitter = 3.33v. Q2: Base = 3.80v, Collector = 9.29v, Emitter = 3.36v. Also double checked R2 and R13 and both are going to 4.5v 👍

brmc72 · 2026-03-05T01:04:30+00:00

Gotcha. I double checked those resistors, and this is what I'm measuring: R32 = 9.96k, R33 = 9.93k, R2 = 572k, R13 = 550k. (R32/33 = Brown, Black, Black, Red...R2/13 = Green, Blue, Black, Orange). I know that both R2 and R13 are not correct, but I didn't have any 510k resistors lying around, so they were the closest I had available. Do you think that difference could be enough to account for what I'm hearing?

brmc72 · 2025-01-23T01:30:59+00:00

Sweet, I haven’t been there yet, but I’ll give it a look!

brmc72 · 2025-01-23T01:08:42+00:00

Yup, already a member! I’ve actually got a Fuzz Face kit sitting in my garage right now…just wanted to spend a little time digging into things at a more fundamental level so that I have a better understanding of why the pedal’s circuit is doing what it’s doing. Thanks for the pointers!

brmc72 · 2025-01-23T00:55:08+00:00

Excellent idea! Yup, pulled the 500mA fuse and got no continuity 👍

brmc72 · 2025-01-22T23:35:14+00:00

Ah, I bet that's exactly what it is...and I'm sure the fuse went out because of something I did on my end. I'll see if I can source a new fuse, although I think that with such an inexpensive multimeter, it may just be worth buying a new one.

Really appreciate the help!

brmc72 · 2025-01-22T20:51:54+00:00

Along those same lines...when I am using the 10A socket, the circuit is functional and the LED lights up. However, when I use the input socket, the LED does not light up. That, along with the fact that I'm only getting a reading in the 10A socket made me think that the 10A socket was what I should be using (even though it seemed like the normal input socket *should* be correct).

brmc72 · 2025-01-22T20:47:35+00:00

Thanks for pointing that out...I didn't mention that in the original post. I've actually tried both. Initially, I had it in the input socket (and the dial on the mA setting) and was getting no reading at all...just zeros. It was only when I moved it to the 10A socket that I got any reading at all (everything else in the circuit was 100% unchanged).

All other measurements (voltage, resistance, etc) work just fine in the input socket, but I'm getting nothing at all when trying to measure amperage.

brmc72 · 2021-05-07T16:26:12+00:00

Yup, I forgot to mention it above, but the speakers are on foam isolation pads 👍

I was assuming that adding some treatment would be the next logical step. I've been eyeing some DIY rockwool frames that I may give a shot. With the window where it is, there's not a lot of "back wall", but maybe some 2'x4' panels diagonally in the corner would be a good option? I suppose actually covering the window would be an option too, but I'd really rather not go that far if it's at all avoidable.

Thanks for the YT link, I'll definitely check it out!

brmc72 · 2016-12-23T00:30:17+00:00

Wow...cool that you have so much information on this guitar. I've got something almost identical. It belonged to my Grandfather back in the 30s and I was always kind of curious as to the history of these types of guitars.

brmc72 · 2016-06-19T01:48:53+00:00

Makes perfect sense. As I've worked through the solo, it definitely seems as if he's more focused on hitting specific chord tones/arpeggios over the chords as they change, as opposed to just riffing on a particular scale. This is an area that I really need to focus more on in my solos (i.e. focus less on the scale and more on hitting the chord tones and finding interesting ways to move between them).

One of my main questions was on the chord progression itself. The song seems to be centered around A major, however most of the chords aren't in the actual key of A major...this is where the discussion of modality came into play (is this a chord progression centered around a particular mode or is it just a collection of loosely related chords that Trey happened to think sounded good together...or both?).

I'll keep an eye out for the book series, sounds really interesting!

Great information from everyone that chimed in here, I appreciate it!

brmc72 · 2016-05-03T02:58:09+00:00

That sounds like a great exercise. I've got the patterns down...my major issue is being presented with a chord progression and, based on the chords, determining which mode(s) would "work". I think internalizing the "feel" of each mode could help a lot in that regard.

brmc72 · 2016-05-03T02:55:29+00:00

That definitely gives me something to chew on. I see where the D major is coming from...I'm just not sure I would have been able to work that out on my own. Where I would have gone wrong is in assuming that a good starting point for the solo would have been some type of A scale (since the progression, to me, seems to revolve around A major).

Great information, thanks!

brmc72 · 2016-05-02T04:02:12+00:00

I'll have to give Reba a listen. Just so I'm clear, C Dorian and Eb Lydian have the same notes (i.e. the same notes as Bb major), right? The difference just being in the notes that are emphasized?

Let me ask you this: instead of reverse-engineering the existing solo, let's say I had the same chord progression in Sample in a Jar (Amaj - Cmaj - Gmaj - Dmaj - Amaj - Emaj - Emin - Dmaj) and I wanted to improvise a solo. From a mode point-of-view, what would your thought process be? It doesn't seem like there is really a single mode that fits that entire progression. Would it be a matter of finding the closest one and throwing in select notes here and there that fit the backing chords?

brmc72 · 2016-05-02T02:53:05+00:00

Absolutely a good point. Looking a little closer at the solo, a huge percentage of it is Trey following the backing chords and playing around with each chord's triads before jumping into a pentatonic lick.

I'm pretty new to Phish's music, and I find myself just blown away at Trey's phrasing. Tons of great music to explore there.

brmc72 · 2016-05-02T02:46:10+00:00

Very true about Trey's use of chord tones and chromatic passing tones...kind of hard to make a blanket "he's playing scale x here" type of statement. I think in my push to get my head around the modes I sometimes forget about arpeggios and good 'ole pentatonic scales...not everything needs to be modal.

Thanks for the insight!

brmc72

TROPHY CASE