Great Cheddar Debug

[Dji]

I posted this downthread in another Great Cheddar post, but haven't received any substantial replies, so I thought I'd try it as its own topic.

I built my Great Cheddar as my first project. I put the thing together, fired it up, and wondered at its glory.

Then I fussed about the rotary switch, which I'd mounted on the same side as the other components. When I put the board in the box, this left me no access to my trimpot, plus I had to put a piece of paper in to insulate my capacitors from the box. This all seemed less than ideal, so I desoldered my switch, soldered it on the other side of the board, fired up the Cheddar... and nothing.

A week of futzing later (no multimeter yet, but I built an audio probe) and, after returning the rotary to its original position, I finally got the cheddar firing again. However, it's no longer quite right in the head.

In three out of four rotary positions, my fuzz pot and my volume pot both seem to have the same function. When I turn my fuzz pot all the way one direction, the volume goes away. Also, those three positions all sound the same: somewhat muted, and fuzzy but uninspiring.

Something's obviously blown, fried, or poorly connected. I welcome any ideas as to how to isolate the bad connection, component, karma, etc.

Thanks!

[Dan N]

I don't know if the leads will still be right if the switch is attached to the wrong side of the board.

I put my trim pot on the foil side to get at it.

In the cheese position the fuzz knob has to be turned backwards to get sound through, depending on your power supply and the trim pot setting.

Did you mention in the other thread something about axial electros? Maybe if you put the switch back to the parts side, and moved the trim and the too large caps to the foil side. You can insulate the cap leads and lay them down against the board.

You'll get it working!

Dan

[joshwatson]

or you could do it like marsstians did mine and move the trim pot externally and then make "position 4" much more usable for different songs.

[Dji]

Once I get it working again, I'll switch out the trimpot for an external pot. I may also move my big caps to the other side of the board.

I'm a bit stumped on tracking down the problem, though--there's a massive volume difference between the one rotary position that sounds correct and the three remaining positions.

Looking at the diagram, it seems like one rotary switch leads through r10 and the p1 trimpot to the fuzz. The other two lead through c7 and r11 and eventually to the tone pot. My transistors are all socketed, so I've swapped out Q1 and Q2 (I only have one spare, so I couldn't do them both at the same time) and seen no effect. I would guess the problem's somewhere between c7 and the tone pot. (Then again, the fuzz is working like volume, so maybe the problem's down that way.)

My audio probe gets sound from the non-ground side of D1, but not from the ground. But from poking around I'm getting the impression I shouldn't get sound from the ground side of any connection. Is that true?

[Gus]

One thing the builders of this circuit should know it the Lorlin switchs I have seen often wear out fast  and they might be very heat sensitive.  I have replaced a number of lorln switches in real lovetone petals.

If you have no money you can sometime open the switch and clean and retenstion the contacts

[Dji]

That makes sense. Thanks.

Thanks to another post on this forum, I've discovered a nearby (suburban DC) electronics shop. I'm going to scope them out today & maybe they'll have a suitable switch.

Given that it was my first attempt at desoldering, this switch has been through a great deal of pain & suffering.