Mobius Strip In My Future: Anticipating the pain

[Mike52]

Against my better judgement, I've started building a Mobius Strip. It is a complex build and I have had problems with simple builds (I can count on one hand the number of pedals that fired right up for me) so I'm anticipating problems with this one. I was hoping there was some great advice on how to test-as-you-go or to debug portions of the circuit as you build. I've searched Madbean's forum and can't really find much in the way of helpful troubleshooting or quality control advice when it comes to the build. It seems like most of them have successful builds or they gloss over the troubleshooting. I was hoping there was some great advice on how to test-as-you-go or to debug portions of the circuit as you build.

I've got experience building amplifiers and the nice thing about that is that there's never a single startup moment; instead you can build phases of the project, put power to them and check voltages and other things so that the final start up sequence is usually pretty uneventful. I haven't figured out a way to do that with pedals yet. And I have no experience with pt2399-based delays.

Anyone have a process they like to follow on complex builds that allows them to debug the circuit at different stages of construction so the final startup isn't so daunting?

 

[Harry Klippton]

Paging @jjjimi84 he's built basically all the VFE stuff

 

[Bio77]

I don't think there is much advantage to testing as you build. You have access to everything on the PCB before you wire it in the box. So, I think it's a little different and easier than an amp in that respect. When you run into problems you usually start probing your way through sections of the circuit, kind of like you are describing but everything is populated.

I've built this one and most of the VFE stuff. The trickiest part is the switching board. You will have to read those docs several times to make sure you are adding the right parts. It's different depending on what you are building.

Other things that come to mind are that they are like PPCB builds in that you are adding parts without referent numbers. Also, the boards are dense, so, be careful and take your time. Lastly, I find sticking to the 1590B box is easier. I've done a few in 125Bs but it takes some planning and sometimes a file to get it to work.

 

[Diynot]

As pointed out around here many a time, Madbean has excellent build docs. Follow them and you will be fine. Also, the instructions for the switching board are separate from the project itself. The Mobius is dense so be extra careful when soldering so that you don’t bridge any pins.

Lastly, I find sticking to the 1590B box is easier. I've done a few in 125Bs but it takes some planning and sometimes a file to get it to work.

Do you mean that the other way around? I use the 125b because of the extra space. You will still need low profile caps, or omit the inner nut on the stomp switch in a 125b.

 

[Bio77]

As pointed out around here many a time, Madbean has excellent build docs. Follow them and you will be fine. Also, the instructions for the switching board are separate from the project itself. The Mobius is dense so be extra careful when soldering so that you don’t bridge any pins.

Do you mean that the other way around? I use the 125b because of the extra space. You will still need low profile caps, or omit the inner nut on the stomp switch in a 125b.

I meant 125B with top mounts. I like that format best, but not all of the VFEs can be forced to that. A 125B with side mount jacks would be easier, yes.

 

[jjjimi84]

I was terrified with my first vfe builds. There is a lot that can go wrong between the tight fit and weird parts they are quite challenging.

The best way I found (like others mentioned) is approach the build like two separate builds. Build the the foot switch board and make sure you have the right diodes and caps and all of that. You can even power it up and test the on off of the pedal.

Then move to the audio board, follow the build docs and have good clean solder work. Just take it slow and don’t rush it.

This build isnt for the beginner it is very challenging but not impossible. Good luck to you, let us know if you get stuck

 

[zgrav]

here are a few suggestions that may help when building VFE projects.

pay attention to the sizes of your caps. you need short ones for the switching board at least. the VFE builds are good skill building projects. make sure you have the right part values and sizes and go slowly relying on the build docs.

the VFE pedals also maximize real estate on the PCB by using the smaller 9mm pots in a few places. those pots have extra legs on the base that fit into holes on the PCB. I think Tayda now carries most of the values you need in that size.

try not to melt some parts on the board while you are soldering the pots into place. I deformed a few box caps on some of my first VFE builds, final result was not pretty, but everything worked.

If you have not already started doing this, it helps to not solder the pots and switches to the PCB until you place them on the board AND in the case and anchor them with the mounting nuts. you can then adjust the position of the pcb board a bit and solder the pots into place. by getting the pots lined up with the holes before they are soldered in place, you avoid having badly aligned pots put stress on the PCB when they are coerced into position. also, you can start by just soldering the middle lug while everything is in the case then take everything out of the enclosure to give yourself a little more room working around the edges of the board.

 

[Feral Feline]

Use finer solder.

If you're using the same 1mm solder used on your amps, get some .5 solder.

Practice with it, as it will have a different melting point and feed rate than the thicker solder you may be used to.

Consider whether the tip on your iron is the rate [edit: “right”(damn auto-incorrect!)] shape, diameter etc for tighter builds.



Most people here do the parts placement in order of height:
Resistors, IC-sockets, then box caps then electrolytics etc;
inspect the solder joints after finishing each component type; test for simple continuity between parts and poke around where you shouldn't have continuity to see if your DMM beeps when it's not supposed to (and if it does, find the solder bridge or whatever is making the circuit behave incorrectly).


I found just switching to a finer solder helped a lot on tight builds. Good Luck!

 

[Bricksnbeatles]

I have a few VFE boards in my inventory that I’m waiting to start. Möbius strip is probably the one I’m most excited for, but the tractor beam should be fun too once I come up with a visual concept for it (given my affinity for Star Wars themes, you would think it would be an easy choice, but I already have something else in the works as a tractor beam). I’m brutally terrified of the parts sourcing part though. I feel you

 

[Harry Klippton]

When I ordered some vfe boards last year or whatever,. I made sure to source all the stuff for the switching boards while I was at it. Hope I'm not assed out on any of the other parts i might need

 

[benny_profane]

Lots of great advice here. Just a heads up, there is a dedicated sub-forum for VFE projects on the madbean forum. Definitely check it out (or post there!) too.

 

[Mike52]

Lots of great advice here. Just a heads up, there is a dedicated sub-forum for VFE projects on the madbean forum. Definitely check it out (or post there!) too.

Yeah, I've been there. Doesn't look like a lot of those folks had much trouble with the Mobius. I'm sure they are more competent than I am. I'd ideally like to find the forum where all the problems are discussed and resolved. But I'm not above making my own mistakes too, ha.

 

[Chuck D. Bones]

I built a Mobius Strip and it was quite challenging. Read and re-read the build docs. Do not substitute parts. Follow the assy diagrams to the letter. As Bio77 stated, the vertical clearance on the switching board is critical. Mount the 78L05, J175 & BS170 as close to the board as possible. DO NOT socket the PIC12F509 and TC7662B; they will be too tall if you do that.. Don't solder the electros or TO-92s until you have test fit the switching board into the box and verified the vertical clearances. If you use board-mounted jacks, the jack holes must be drilled in exactly the correct locations. Use the chassis as an alignment jig when soldering the jacks.

Inspect as you build because you do not want to end up reworking these boards. The only in-process testing I recommend is to power it up before installing the ICs in sockets and verify the correct voltages on the power pins of the PIC, PT2399s and TLE2074.

Have fun & good luck!