VIIB Build

[slowpogo]

I don't know if anyone else went ahead and built their VIIB even before build docs are posted...well I couldn't wait! Without biasing instructions I'm just guessing but I've got it in a place where distortion is minimzed and the vibrato happens sometimes (see below). Running at 9V, it draws 10-12mA. I'm testing with Depth turned up pretty high and Rise Time turned down. Here are a few initial issues..

- I get sound in bypass, then volume jumps up 5-6db when pedal is "On"
- LED does not light at all. Using what I thought was the recommended red/blue one from Small Bear, still works when testing with my multimeter
- only time I hear the vibrato effect is if I turn the Rate knob up from full CCW, then the vibe comes in briefly (and sounds great!) but quickly flattens to a regular signal

Only substitution is a 500k trim instead of 470k. BBD is a Panasonic MN3207 from Banzai Music (text is very faded). Clock is an MN3102 I stole from a previous build so I know it works. I'm using the posted footswitch and the relay bypass system does seem to work, in that it will latch on/off with quick taps, but is momentary with longer hold times. I'm not sure how to switch between True Bypass and Classic modes.

No expectation of comprehensive help at this early stage of the board's availability but if anyone wants to chime in that'd be great.

 

[Robert]

Hmmm... OK, lets get the simplest thing out of the way first, because it's also a good indicator of whether the digital portion is working properly or not. You did say the relay bypass was switching on/off, so that's a good sign.

Can you confirm that the dual LED is common cathode?

 

[Popnfreshbass]

I’d beware of Banzi stuff. I’ve gotten burned by them before. If you have a spare v3207 in a chorus or something try putting that in too see if it works

 

[Hirti]

I’d beware of Banzi stuff. I’ve gotten burned by them before. If you have a spare v3207 in a chorus or something try putting that in too see if it works

I also bought two MN3008 on their website a few years ago that turned out to be fake…

 

[slowpogo]

Hmmm... OK, lets get the simplest thing out of the way first, because it's also a good indicator of whether the digital portion is working properly or not. You did say the relay bypass was switching on/off, so that's a good sign.

Can you confirm that the dual LED is common cathode?

The LED is common cathode, it's part 2306B from Small Bear.

I’d beware of Banzi stuff. I’ve gotten burned by them before. If you have a spare v3207 in a chorus or something try putting that in too see if it works

I tried a working 3207 from my Low Tide build and got the same behavior. I've actually not had any problems with Banzai but it's good to know others have.

 

[fig]

I've actually not had any problems with Banzai but it's good to know others have.

It seems to be hit or miss with them, which could equate to unreliable suppliers and/or QC.

 

[Stickman393]

Takmans, PRPs, look at all dem pretty resistors.

 

[Robert]

Hold down the footswitch while applying power, this will switch the pedal to Buffered bypass mode.

See if the LED lights then.

 

[fig]

Alternatively, you could close your eyes and click your heels 3 times...

...this puts YOU in buffered bypass mode.

 

[slowpogo]

Hold down the footswitch while applying power, this will switch the pedal to Buffered bypass mode.

See if the LED lights then.

Tried this. The LED does not light after switching, but the volume is now consistent between on/off in the new mode. Otherwise the behavior is identical.

Takmans, PRPs, look at all dem pretty resistors.

People disagree about resistors having a "sound" but I'm convinced Takman carbon films do actually warm up the signal path, in a nice vibey way.

 

[Robert]

That's puzzling.... The microcontroller is switching, otherwise the relay wouldn't latch/unlatch...

I can't think of any reason the LED wouldn't light aside from it being the wrong type. Can you measure the DC voltage on the R and G pads of the LED in Active and Bypassed mode?

You can do this with the upper analog board disconnected and out of the way. The digital board will function without it.

 

[slowpogo]

Finally getting back around to this! Life got hectic, as it sometimes can do. I did this test with the analog board detached.

Bypassed (draws 2ma)
G = 4.01v
R = 0.01v

Active (draws 3ma)
G = 0.02v
R = 4.98v

I clipped out the LED to test with my multimeter. Putting my red probe on the center leg, it will light when I touch the outer legs with the black probe. But not the other way around. Which means it's common ANODE, right? Darnit.

This is actually Small Bear's mistake, at least as the order is concerned. I ordered the common cathode part and that is what's on my invoice, but they sent this one. I'll see if they can send a replacement, never had to test their customer service like this before.

LED aside, what might be causing the other bad behavior?

 

[slowpogo]

any estimate when we will get build docs, or at least a schematic for this? I don't think I can debug it without the schematic.

 

[Robert]

I'll be working on more build docs later today. This is one of the next ones on the list.

 

[Robert]

Here's the schematic / component layout. This doesn't include the parts list, wiring diagram, or drill template yet, but should be what you need.

https://docs.pedalpcb.com/project/VIIB-PedalPCB-Preliminary.pdf

I would start by ensuring that the LFO is present on pin 9 of the LM13700 (turn Rise to minimum so it isn't lagging).

 

[slowpogo]

Great! thank you

 

[zombie_rock123]

Sorry to chime in without help on a troubleshooting thread but massive thanks to Pedalpcb for the doc, I've got dry signal but no chorus with tested BBDs so this will hopefully help solve

 

[slowpogo]

I would start by ensuring that the LFO is present on pin 9 of the LM13700 (turn Rise to minimum so it isn't lagging).

I'm getting a variable voltage reading on pin 9 (fluctuates up and down). which I'm guessing means the LFO is present?

I can't figure out why the vibe would be there just like I expect, then quickly flatten out. A short, somewhere? The board looks good and clean. My only idea at this point is to go step by step through the schematic and check continuity on everything.

 

[Wizardofwoz66]

Is there enough room on this to socket the ICs? I always install sockets first and didn't want to do it if not

 

[slowpogo]

Is there enough room on this to socket the ICs? I always install sockets first and didn't want to do it if not

Yes, in fact there are several pictures above demonstrating this

btw I still haven't gotten this to work. Pretty much given up on it at this point