BYOC Triboost Problems

[befey]

I have the V1 version. I am having a couple problems with my build.

First, the LED is not working right. Sometimes it comes on, sometimes it doesn't. Sometimes it comes on for a second then goes off.

Second, when the selector switch is in the first position. The Hi/Lo switch is to the right. The volume is lower than bypass even at maximum on the knob. The Hi/Lo to the left gives lots of boost.

The selector switch in the second position gives lots of boost.

The selector switch in the third position has volume lower than bypass even at max on the knob.

I don't know which mode is which in the selector switch. I'm also not sure which is left/right on the Hi/Lo switch.

Can anyone help?

[MaxPower]

Schematic?

[befey]

The instructions are here: http://byocelectronics.com/triboostinstructions.wps.pdf

I haven't seen a schematic anywhere.

[befey]

There's this one, but it's slightly different than the one I have.

http://thermionic-studios.com/wiki/images/1/1f/BYOC_TriBoostSchematic.png

[idy]

your first position= rangemaster,  middle =LPB and last position= MOSFET. The Rangemaster turned the LED red, the LPB blue, and the MOSFET green. Do you have the right tri-color LED? You may need to check the solder joints on the selector switch as it chooses circuits and LED leg.

It seems your LPB is working, the Rangemaster has an issue around the tone switch and the MOSFET is not working at all.  Are you using transistors that came with a kit? What kind? Are you sure about the transistor orientation?

The three position tone switch affects only the Rangemaster. Middle position is the old fashioned treble booster. On direction adds a cap in parallel for more low end, the other direction adds a bigger cap for even more lows. It is common but a little disconcerting for the obsessive that the positions are out of order: mid, treble, full range.

[befey]

That schematic is for the second version. Mine is the first version. The differences (I think) are that mine has a red Led, and the toggle switch is only two position, Hi/Lo.

I'm using all the parts that came with the kit. I matched the transistor orientation to what was printed on the PCB. The germanium is socketed and I have tried it both ways around. I have it oriented in the way that gives a boost when the first mode is selected.

But the rest of what you're saying makes sense. Are there any measurements I can get that would be helpful to troubleshoot?

[idy]

People love to see pictures here! This may sound obvious, but you have made a mistake and can't see it, maybe someone else will. You must double check all resistors for correct value. Did you measure them with  a meter before installing? One wrong value and the Mosfet booster won't work.

I see your version now. Did you get this a long time ago? The ones I built I bought like 10 years ago and had all the switches and pots attached to the board. You may easily have mixed up a wire or two.... The bad behavior on the range switch makes more sense now. In the newer model, even leaving the additional capacitors off the board would make no difference, you would get sound in all three positions.

This is a really handy box to have and teaches a lot about circuits and the sounds of different boosters. You are almost there!

[befey]

https://www.aronnelson.com/gallery/main.php/v/Schematics-etc/20190310_140112.jpg
https://www.aronnelson.com/gallery/main.php/v/Schematics-etc/20190310_140333.jpg
https://www.aronnelson.com/gallery/main.php/v/Schematics-etc/20190310_140415.jpg

I got this pedal a really long time ago! I built it back then and had exactly the same problems with it. Maybe the LED worked back then. I gave it to a friend to troubleshoot, and he gave it back to me with all the wires cut and said he couldn't figure it out.

So I finally got some better tools and decided to rewire it and try it out again. Only this time there were bits of old wire and solder stuck on all the lugs.

So here we are. The fact that the whole thing has been rewired and still has the same problems leads me to think it's gotta be something on the board.

There's a volume cut on the Hi switch of the germanium mode, and a volume cut on the MOSFET mode. And the LED doesn't turn on.

[idy]

Check out the resistors around the BS170. The instructions highlight on page 11 the components for the "clean" (mosfet) boost. With power disconnected you should be able to use an ohm meter and see if they resistors match the value. I think you have a 1M where there should be a 10M. Not sure that would really do it... but check them all. Being in circuit may throw the values off, but in this thing you may be able to verify that they are, for examlple 2.7k and not 27k, for example.

After that the next idea is make a probe, just a little cap soldered to a wire at the end of a cable with a ground clip, and a 1/4" jack at the other end. Plug in a sound source (anything) to the pedal and trace away.
You can trace the signal and find out where it cuts out. Is it getting to the transistor and dying? Mosfets are a bit fragile...

[befey]

The resistors all look right to me. I'll check them with a multimeter to be sure.

The audio probe is a good idea. I will need to build one of those too. But... I do get some signal all the way to the amp even on the modes that aren't working right. They're just very quiet. Almost goes up to unity at full clockwise on the volume pot. Just not ever louder than unity. Will the audio probe help diagnose that?

[befey]

The 100k resistor in the clean section is measuring 47k. I don't see a reading of the bands that corresponds to that, but maybe I'm missing something.

The 62k is reading 42k.

In the germanium section, the 470k is reading 22k.

I'm measuring by touching the solder points on the back of the board.

[aelling]

https://www.aronnelson.com/gallery/main.php/v/Schematics-etc/20190310_140112.jpg
https://www.aronnelson.com/gallery/main.php/v/Schematics-etc/20190310_140333.jpg
https://www.aronnelson.com/gallery/main.php/v/Schematics-etc/20190310_140415.jpg

A lot of those solder joints look bad, especially the ones for all the wiring, with what looks like a bunch of bridges.

https://karpova-lab.github.io/cerebro/_images/soldering101.png

[befey]

Some of the pads for the wiring are so close together I assumed they were meant to touch. Is that not a thing?

[aelling]

Some of the pads for the wiring are so close together I assumed they were meant to touch. Is that not a thing?

Those pads seem to be connected through traces on the PCB, so it's not necessary to solder them together like that. But it's not just that, some of the solder joints look cold and some with too much of solder on them.

[bluebunny]

The 100k resistor in the clean section is measuring 47k. I don't see a reading of the bands that corresponds to that, but maybe I'm missing something.

The 62k is reading 42k.

In the germanium section, the 470k is reading 22k.

I'm measuring by touching the solder points on the back of the board.

In general, if you're trying to measure resistors when they're in-circuit, then your results will be inaccurate.  This is because the resistors are, in general, in parallel with the rest of the circuit (which is why all your values are lower than you expect).  You'd need to lift a leg if you want accurate readings.

[befey]

I'll try to touch up the wiring joints. They were really difficult to get clean joints because of the way it had been taken apart before. It doesn't seem likely that's where my volume drop is coming from though? Maybe the LED weirdness. Working the wires didn't seem to change LED behavior though.

Is it possible to tell if those resistors being incorrect would cause the volume drop? It seems strange that those ones would measure off, but the rest are almost dead on. I guess that's what you mean about them being in parallel?

Anyway, I'm getting a bunch of assorted components today, so I'll try putting in new resistors that I've measured beforehand.

[idy]

One messy solder joint would surely do it. It's happened to all of us.

The resistors: can you read the color codes? Do they match what they should be? Resistors don't just "go bad" or vary from specified value by much. Replacing them I would not do unless you know there's a mixed up value. Some of yours have four bands some five. Can you compare the codes to the schematic/ values on the board?

Can you measure the voltages on the three legs of the MOSFET?

The plus side of all this trouble-shooting is that you end up understanding a circuit at least a little more.

The LED: check where the voltage is dying. Those foot switches will become intermittent if you linger a few seconds too long with the soldering iron. The epoxy the terminals are sitting in gets soft, things move just a smidgen and viola....dodginess. Again, don't bother replacing everything but test test test. Unless you like replacing everything. The shotgun approach works sometimes.

[aelling]

https://www.aronnelson.com/gallery/main.php/v/Schematics-etc/20190310_140112.jpg
https://www.aronnelson.com/gallery/main.php/v/Schematics-etc/20190310_140333.jpg
https://www.aronnelson.com/gallery/main.php/v/Schematics-etc/20190310_140415.jpg

Just looking at the pictures of your board again and it seems you have the 47pF ceramic disc cap in the wrong spot, it needs to go next to the BS170 and the green .047uf film (473k) needs to go where the 47pF is. Reverse those and report back.

[idy]

The 47p isn't on the schematic for the later version. Maybe a radio shunt (to ground) on the gate... or feed back... either way, putting a big fat cap there would cut gain to...almost none.

You can go to BYOC and find the schematic for the later version, if you are interested. I can't imagine trying to trouble-shoot something without at least trying to find or sketch a schematic.

[idy]

It is almost certainly a  RF "shunt" capacitor on the gate. Part of the original AMZ Mosfet Booster that BYOC "lifted." Check it out.
The one change they made is the original had a real gain control, a pot in series to the "source resisitor bypass cap." The BYOC version is just set to maximum gain so it can share one volume knob with two other circuits.