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One step forward, two steps back I'm afraid.

After taking this picture and putting everything back together I fired up the fat pants, only to have no sound whatsoever come out... Bypassed, Buffered, or with the effect on. Nada. When I was having problems with the footswitch (right before it died) I would at least get sound with the effect bypassed.

So whenever I get some free time (hopefully this weekend) I'm going to have to address where I think the problems are.

1. The footswitch
2. The DPDT buffered/bypass switch
3. The jacks themselves
4. Grounding problems
5. Broken Wires

etc.

Ugh. All I wanted in the whole wide world was to be able to close the pedal up and have it work but unfortunately it was not to be. This is why even the lowly fatpants was a bit ambitious for my first perfboard build. But such is life. When it was working it was my favorite pedal so at least I have that to motivate me to get it working again.

So, earlier today I completed my fatpants build (just have to install the indicator LED) - I fired it up to see if everything was working and much to my chagrin it was. I had the buffer working since forever but only recently got the boost section functioning.

I know there's no good reason to use carbon comp resistors but I did anyway. When my 12v adapter comes in (already got an appropriate charge pump and internals to run at 23v btw) I will have this running at the full mccoy. If not for the zener diode it would work up to 15v (or 30v internally) but I'm going for as close to the echoplex as I can.

Instead of a TIS58 I used a MPF102 for Q1 - I've read that this is very close to the TIS58 and significantly cheaper so I went with it. Q2 is a standard J201 which I like very much.

It was kind of a pain to get everything working properly because I included a true bypass/buffer dpdt switch so I could hear the effect of the buffer a little better (and potentially use it in conjunction with my buffered pedals like my modded SD-1), but after studying the sunking build guide I was able to get everything working properly. The trickiest part was the "sw" part of the board (I copied the layout of the PCB onto perfboard because I'm not creative enough to design my own) but once I figured that out it was smooth sailing.

I still have to clean a few things up (the fat control isn't insulated very well so if I jostle it around I get jumps in volume and intermittent scratchiness) but overall I'm pretty much there in terms of the build.

I also used exclusively red wire so it was insane trying to get everything wired up. For my next few builds I will definitely do exactly the same thing because all I have is red wire and I don't want to spend money on more. But in a perfect world I would use different colored wire.

Hmmm

I don't have a demo video yet (and am hesitant to say when I will post one if I do at all) but you've all seen the youtube video of the fatpants in the 1590A enclosure. It sounds like that. I built mine in one of the tiwanese BB seconds enclosures that Small Bear sells. I'll post some pictures later so you all can see just how hideous and awful the inside of it looks - if you're squeamish or OCD I would just skip coming back to this thread once I post photos lol.

Really, really like this pedal though. Gorgeous clean sounds out of it and later on if I get some alone time I will report on how it sounds into a cranked 1974x baby will (18w marshall clone).

Put the diodes after the output cap to ground.

The only other reasonable place to put them would be at the gate of Q2, but you won't have anything more than your pickups driving them, so there won't be much if any distortion.

FWIW, you can tinker with the biasing and turn the fat all the way up and it'll distort with hotter pickups.

There are better circuits IMO for doing this, like pedals that are designed as dedicated overdrives. For one thing, there's no tone control or treble cut after the diodes if you just tack them onto the circuit, so it might not sound very good.

Thank you for the help. That's one thing I was curious about - the buffered bypass is essentially just the first half of the circuit but I just barely know how transistors function in the abstract so I figured (after looking at a very simple circuit that used a single transistor to clip a pair of diodes) maybe there was a way to use Q1 to do the clipping and Q2 to amplify like normal. I'm hand on heart honestly looking up the difference between voltage, current, and resistance as I type this.

I've heard before that Q2 starts to clip some at the highest "fat" settings - I kind of secretly hoped that there'd be one or two components you could change (like in the jfet vulcan for example) that would up the gain of Q2 and allow you to use the "fat" control as a "gain" control.

Lastly I had found a dead-simple treble rolloff circuit which I was planning on using as a stand in for the "soft" switch. The whole concept was not dissimilar to something like a transistor-driven prince of tone, but with that just magical character you get with these echoplex-type boosts.

When my fatpants was half-working (something happened to the charge pump and it only ran on 10.6v) it was the best sounding pedal I had (charge pump #2 is in the mail)... I just was curious about how it would sound if it was a drive pedal itself. Really I need to just leave it well enough alone - just getting it to work in the first place was pretty impressive for a luddite like myself.

At any rate thank you again and my apologies for the long post. I frequently speak at length out of habit for no good reason... It's something I'm trying to improve about myself.

Would I connect the start of the circuit to the source of Q1 and then to ground? I imagine I'll need a capacitor in series with the clipping diodes to roll off some bass?

Also, (and this is a separate question) if I wanted to get Q2 to clip, would I increase the value of R9? I was reading about the jfet Vulcan and he uses diodes to prevent hard clipping of the transistors, would this be necessary/a good idea in this application?

To be clear I'm just curious. Thank you in advance for any and all help.

Edit: when I say curious I mean I'm definitely going to add this feature to the fatpants... I'm just not super well versed in circuit design so I'm uncertain as to how to proceed.

Removed the Zener - voltage went up .15v from 10.6 to 10.75 - this is also with no load on the circuit so I'm thinking I might just order a whole new charge pump and parts. Once the 3pdt switch is mounted it's really hard to add/remove the other components.

As always thank you again for the help.

Oh oh oh derp.

Okay well in that case new results inbound.

So, this is sort of a necro bump, but I've been busy and had a hard time getting around to messing with the fatpants.

I've got voltage to q2 now (may have said that already), but the charge pump is still a problem. I disconnected everything from the charge pump except the power supply and it still reads 10.6v with no current draw coming from the circuit.

At this point I think I'm just going to take out the 12v zener and solder in a jumper. If that doesn't work I'll just order another charge pump.

Besides the charge pump though the circuit seems to be working fine.

Thank all of you for your help - and I will report back with more findings as they occur. But I'll just edit this post so it doesn't get necro-bumped every time I get something working again.

Yes, when I was ready to order the fatpants circuit the boards here were sold out so I copied the schematic/layout on some perfboard and used the 3PRR to power it. The wiring is hideous, and there are solder globs everywhere, but it works.

A short post-charge pump is likely because of how messy everything is. I'll re-check the wiring as it goes from the charge pump to the board as that's the most likely culprit.

Thanks again for your help Rob (and Matt) - I kind of bit off as much as I could chew with this one.

First off, thank you for the replies! I do appreciate it.

Pads are not jumpered, or at least I've not soldered them at all

Zener is a 12v (originally I had planned on using this with a 12v supply for ~24v to the circuit)

I will check for a short and get back to you guys - FWIW the board put out ~18v off a 9v batter before I attached everything so a short is a very real possibility.

edit: Just measured and it looks like I'm drawing 114mA but I have no idea how much I should be drawing - for reference this is a fatpants build that I made on perfboard so w/e current draw requirements that has is what mine are.

So, I posted another thread in the general discussion, but as it turns out all of my problems were either misinterpretations of the schematic/layout or bad solder joints, so I fixed those.

My charge pump however is still not working right - It's the 3PRR which is a charge pump/true bypass thingy.

I'm seeing (with a 9.6v input) ~10.3v right now at the +18 pad. I'm seeing ~9.2-9.3v at the + pad of c3, and ~10.2v (sometimes 10.3v) at the + pad of C4

I used 5818 diodes (I think those are the ones - their part number/designation is one higher than the ones recommended in the build document), and the charge pump by itself worked fine. Thing is they do take out about .3v - and with R2 the I/C (LTR 1054) is seeing ~8.2v or so.

Pin 1 on the LTR shows 1.15v, Pin 2 shows 1.5v, pin 3 shows 0v, and pin 4 shows -.95v
Pin 5 shows -1.5v, pin 6 shows 2.6v, pin 7 shows 1.45v, and pin 8 (which I think is getting 8v from the supply)

Also it seems like a ~1v drop for a 10r resistor is a bit much so I'm going to check r2.

So, my suspicion is that my charge pump is torched, because if I'm looking at this correctly (and I may not be because I'm a huge newb) I should be seeing a combined 9v from the outputs of pin 2 and pin 4 from IC1. Is that right? Do I need to get a new IC?

Thanks in advance for the help and I may socket the IP next time I make one of these haha

So, I tried to do my best to copy the fatpants layout seeing as right now they're unavailable.

I used the 3PRR and ran the tip of the input to a dpdt switch - the first side goes into the footswitch/charge pump (for true bypass) and the other side is connected to the "in" (which is in turn connected to the "in" part of the circuit)

Also, I've connected the "sw" portion (that activates the buffer) to the two unused prongs in the 3PRR (middle and bottom all the way left if you're looking at the PDF) so that when I'm on the buffer setting and the footswitch is "off" it should still be buffered. I've since disconnected these so that the buffered setting no longer works, right now. As it turns out, for some reason that I still can't figure out, while all of the other parts of the 3pdt switch work right, those two prongs always share an electrical connection (and because of this I would always be running the buffer and never the effect)

Now, I have a few problems:

- The charge pump which originally worked great now only reads 10.6v (from the +18v out) when plugged into a 9.6v power source. Interestingly enough if I move the black end of my multimeter to the -9v output it reads 12v, which is still way short of 18v
- The "on" setting for the effect only engages the buffer - the "soft" and "body" switches as well as the "fat" control have no noticeable effect. The level control only turns the effect off when turned fully counterclockwise but otherwise has no discernible effect on volume.

I've checked my wiring and it all looks okay (aside from being a complete rat's nest) - I have photos of the board that I'll attach when the email sends (cell phone photos but you can see everything). I don't know if it will help but I sure hope so.

So, in summation,
- Only getting the buffered output even when the effect is engaged (which makes me think the "sw" part is connected somehow but I've double and triple checked and I can't see where the connection would be)
- I'm like 8v shy of where I need to be so even the buffered output is slightly lower volume than bypassed.

I would love any help you guys have to offer but I will continue to work on this and post again if I do ever figure out what I've messed up.

Edit: I'm using the LTR1054 or w/e the one with the 14v input is, and an mpf102/j201 for q1 and q2. I've omitted the portion of the charge pump to the "left" of R11 and "below" R9 if you're looking at the fatpants 2013 PDF.

Double edit: Q1 is seeing voltage but Q2 is not

Triple Edit: (I'll keep updating the first post with my progress so the thread doesn't get bumped to the top) - Cold solder joint on R11, fixed, now Q2 is seeing voltage - at full bias it's ~10v at the (drain? that's what it looks like from the diagrams), and .45v at the source, and 0v at the gate. Again I'm about as green as they get so this is just me working backwards from the diagrams using the internet. There may be some more cold solder joints so I'm going to troubleshoot those.

Still trying to figure out the charge pump and the whole buffered/true bypass switching.

I just wanted to make sure I was correct on this - for the 3PRR - the road rage with the 3pdt switch incorporated - there's a hole next to the bypass pad (which is a square). Can you wire up a spdt switch to that and leave one prong empty to switch between buffered and true bypass? Or am I completely off on this?

The project is a perfboard fatpants minus the charge pump (which is what I'm using the road rage portion for)

Thanks again for any help. If I get it up and running before a reply I'll just post here with my results.

So, it turns out I had one of those small perfboards you can get from pedal parts plus laying around - I just ended up buying the charge pump and I'm going to do the EP portion of the circuit on the perfboard. It doesn't need to be in a 1590 enclosure so hopefully it will turn out alright.

I'm really looking forwards to getting started on the project. If I get it completed and working I'll post a thread in the completed builds area/

Hello, I was interested in doing a fat pants build but it seems as though all the boards are sold out.

Does anybody know about how long takes for the shop to get them back in stock?

I had planned on doing the build for a while but haven't really had enough free time until this upcoming week to actually sit down and build the thing.

I saw Haberdasher has PCBs available for discontinued builds, but AFAIK the fat pants isn't discontinued, just out of stock.

Thanks for any help.

Thank you for the quick response!

So, from the datasheet I found for the J201 it looks like it can handle ~24v.

You said you have a MPF102 in yours, I imagine that means you're using the J201 in Q2?

Also, on an unrelated note I'd like to thank you for making those listening notes on diodes - they've been tremendously helpful!