Ludwig Phase II Clone Debugging and Miscellany

[Vince_b]

I have an other quick question. There is a resistor labeled "Ralt1" on the console board, is it the spot for Rtaper 33k?
And there is an unlabeled spot for a resistor just to the right of RF33, should it remains unused (I'm not talking about the one next to R74 in the top right corner)?

[pinkjimiphoton]

if it follows the original nomenclature, that may be where there was a resistor piggybacked on some of the units we examined.

[Vince_b]

That might explain this particular unlabeled spot for a resistor.  After looking at the build document again I realised that Ralt1 is only needed if you use a particular transistor and I found the correct place to put Rtaper. I couldn't find it before because it wasn't labeled on the physical board, only in the build document parts placement diagram.

[pinkjimiphoton]

diggit...well, remember, you guys are the first to take the plunge, so those of us holding back are waiting to see what you guys do....and learning from it all.

somehow,i gotta condense ALL the info into one file we can host somewhere for posterity.

[R.G.]

There were a couple of quirks in that layout. I think most of them got documented in the latest version of the documentation.  You might go to geofex and get the latest. It's possible some of them were missed. This layout did in fact verify some of my concerns about the Ludwig when I first looked at it. It's big, and complicated.

If you'll post any oddities you find, I'll try to work through them. I'm at a bit of a disadvantage on this, as I'm working the booth at the Dallas Guitar Show this weekend, so I'll have to follow this in bits and pieces for the next couple of days.

There are some places on the PCB where I diverged from the original design by putting on the PCB some mods that Ludwig did as after-PCB mods. I did the PCBs so the original circuits could be followed 100%, but added locations for putting the off-PCB mods there as well. So there are additional places for parts on the PCB. In addition, I put the ability to use a 2N6027 PUT instead of the 2N2646 UJT in the animation section, which added a couple of resistor positions. I think the latest PCB documentation at Geofex addresses these.

But give a look and compare. I would normally build up my board set and list any bugs or changes needed, but I'm realistically not going to have time to do that for a couple of months yet.

[Vince_b]

This project is so big and it haven't been built by many people yet so I'm not surprized that there might still be a few quirks that haven't been found in the layout. By the way, how many people have completed their clone right now aside from Keppy?
I'm going to list every bugs that I find to makes everyone knows about them and you will be able to correct them in the documentation when you will have the time. There is no rush, as far as I know I might be the only one working on this project right now.
At the moment, the only thing that I found that should be added to the build document is a note saying that Rtaper isn't labeled on the actual pcb. To know where it has to go, you have to look at the parts placement diagram. It ain't a big problem, but I stared at the boards for a long time looking for where to put this resistor before trying to find the right place by looking at the diagram.

[Vince_b]

Some other things that people should take note:
- Q2 is not labeled on the pcb. But as it is the only TO-18 transistor, it's not hard to find where it should go.
- On the Bill of Material, Q3-8 are listed as NPN TO92 but it should read instead: "Q3,Q4,Q7,Q8" because Q6 is already listed as NPN TO-220.
- The switches listed on the Bill of Material do NOT all have the same mounting height. The 3PDT are actually taller than the DPDT. To make sure to get them all at the same height you have to mount them on the enclosure FIRST, then solder them to the pcb. Otherwise they won't fit right.

[digi2t]

Thanks for the check on the parts list.

I also found these adapters at Digikey. They should be fine for this project, and at a very decent price.

http://www.digikey.ca/product-detail/en/PSAA20R-480/993-1045-ND/2384488

http://www.digikey.ca/product-detail/en/PSA15R-480PV/993-1117-ND/2635779

The prongs are sold seperately;

http://www.digikey.ca/product-detail/en/RPA/993-1054-ND/2384507

The beauty here is for our overseas brothers. These adapters will work automatically from 90 to 260 vac, and the appropriate prongs can be purchased to suit the country's power outlet. About the same price as Mouser, but I find Digikey shipping more reasonable for me (8$ vs. 20$  )

[Keppy]

Those appear to be from the same product line as the one I used. Good find!

[digi2t]

I've started my build, but something was bugging me about the pot value. I don't know why, but to ease my mind, I decided to remeasure the pot resistance.

The pedal pot IS NOT 5K. I made a mistake by not completely diconnecting the wiring before measuring, that's why I got a nice 5K reading. With the wires off, it comes in at 11K. Yes... 11K. A 10K should be fine though, since we're not using the ends of the pot travel.

My sincere, and profuse, apologies if this created any undue problems with anyones build. Just a bonehead move on my part.

I've already face-smacked myself a few times, but if anyone else feels like giving me a shot as well, feel free.

R.G., you'll have to update the build article, including maybe the section on faking the pot. Also, transistor QF+1(NPN) is not listed on the BOM. This transistor is a 2N4401 in the original units.

[R.G.]

Source updated and on line.

Actually, Qf+1 is listed in the BOM. It's listed as a 2N5551, which (I think...) works fine in this application.

I think I caught all mentions of the rocker pot, but I'm error prone. If anyone finds one I missed, let me know.

[Keppy]

Hmmm. I wonder what change would be made if I corrected mine.

[pinkjimiphoton]

might be why your treadle was self-oscillating, keppy. probably give ya a better sweep with a wider sweet spot.

[R.G.]

I suspect little, or none. There's a big adjustment available on the rocker, and as long as the rocker pot is enough lower resistance than the input resistance into the circuit, it acts like a linear voltage source in series with a modest resistor - about 1.2K for a 5K pot, about 2.5K for a 10K pot. I had to go through those numbers to come up with the "just use a 100K wah pot" circuit.

10K is by far a more common pot value, though, so it's worth changing the instructions for those who come after us.

It would be interesting if you wanted to mess with it and verify that. I'm just guessing, as I haven't done a lot more circuit analysis on it.

[Keppy]

might be why your treadle was self-oscillating, keppy. probably give ya a better sweep with a wider sweet spot.

Nah, the oscillations were cured with the updated trimming procedure. You might be right about the sweep, though.

[RonaldB]

In the document on GEOFEX (wiring guide) there are two connections for DC.
DC1 and DC2, do we have to use both or just one?
I think Pwr Com is the GND from the adapter?

RonaldB

[R.G.]

Actually, those are AC/DC1 and AC/DC2. The original would have used a center tapped transformer, with one end of the winding on each of those, and the center tap on the "Pwr Com" pad. I preserved that in case someone wanted to use a transformer instead of a DC power supply.

If you're using a DC power supply, connect the (-) terminal to Pwr Com and the (+) terminal to either AC/DC1 or AC/DC2, or both. The Principle of Parsimony says only do one. What's inside those pads is just the two rectifier diodes.

[RonaldB]

Oke thanks

[digi2t]

Just a thought, since I'm in the middle of my build here;

For the "Console" board, I think it's best to solder the trimmers onto the back side of the board. This will allow full time access to them, avoiding the hassle of pulling the board out to adjust them.

I don't know if it's been already mentioned or not, and pretty much common dog f*ck I know, but I just thought I would throw it out there.

Back to wiring now.... YUMMMM!!!!

[pinkjimiphoton]

has anyone else got it up and running yet?

i haven't even begun to populate mine yet...