tube tremolo kit - first build

[drfreakypants]

Hi, First time posting, first build.  I put together the "officially licensed circuits" "Darth Fader" tube tremolo pedal recently.  I was shocked when I hooked it up and it mostly worked in terms of the signal and the effect.  There are two problems, and I'm not sure how to go about debugging them.  Firstly, the LED is not lighting up. Second, there is a substantial hum that kicks in when I turn the effect on.  Any suggestions on debugging these problems would be greatly appreciated.  I'm at work so I don't have pics of my particular build right now, but here is a link to the pdf of the instructions for the pedal:

http://www.olcircuits.com/documents2008/olc_darthfader_buildguide.pdf

In terms of the LED, I'm sure I got the polarity right.  The way they say to hook up the LED to the 3PDT looks different than I have seen in other pedals.  Usually the negative lead of the LED goes to terminal 4 of the 3PDT and in this design they have it go to 2.  Could just be a bad connection somewhere, but I was pretty careful.

As for the hum, could just be the wall wart, and I don't currently have another one to try, but I suppose I should get another.  Any other ideas about the hum would be appreciated.

[GGBB]

There's one huge omission in the build doc - they don't ground the stomp switch.  That's probably why your LED doesn't light up.  Connect either the top middle or bottom left lug (when looking at the diagram - they are connected to each other so it doesn't matter which one you use) to ground - the sleeve of the input jack is probably the easiest place.

As for the hum, could very well be your power supply, could be ground loops or other grounding issues.  Eventually someone will probably come along and point you to the debugging thread, so I might as well do it now: http://www.diystompboxes.com/smfforum/index.php?topic=29816.0.  But I don't expect that to be of much help in diagnosing hum issues.  Use the search tool, there are plenty of threads on pedal hum here - there can be many causes.

[drfreakypants]

thanks GGBB!  I'm not experienced enough to find those kinds of omissions.  I'll try grounding the switch.

I figured I would try a different power supply when I come across one.  thanks for the link to the debugging thread as well.

[drfreakypants]

Hey, thanks for the suggestions!  connecting the LED to ground solved the LED problem!    but the hum persists  

Here is a pic of the wall wart:



here's a picture of the build (sort of shy about this, being my first one and all - don't laugh )



maybe this can give some insight into what I can do to decrease the hum.

[duck_arse]

you could try twisting the heater wires together (pins 4 and 5?).

[GGBB]

Try moving things around so that the AC wires to the power supply board aren't close to any of the audio signal wires.

[Paul Marossy]

you could try twisting the heater wires together (pins 4 and 5?).

+1

Try moving things around so that the AC wires to the power supply board aren't close to any of the audio signal wires.

+1

[Lurco]

Is your chassis grounded at all? I.e.: is there a wire or otherwise electrical connection between circuitground and the metal box? (since you`re not using metal jacks that would provide this connection automatically).

[drfreakypants]

Ugh!  So I've been over the wiring several times, and I just don't find anything wrong.  I tried grounding the jack to the enclosure and that didn't help the hum.  Does anyone have a suggestion for systematically debugging the hum, maybe in particular that everything is grounded correctly?

The olcircuits.com people suggested moving the power rectifier/filter pcb away from the signal wires which means redoing all the wiring to that pcb with longer wires and moving it to the other end of the enclosure.  I would rather do a bunch of testing to rule other things out first before I do a bunch of desoldering and rewiring.

[GGBB]

If you can get hold of a 12VDC regulated power supply, try powering the pedal by connecting this directly to the main PCB power in and see if the hum goes away or changes.  If it does, then the hum is related to the AC board and or wires.

Edit:  You can create a 12VDC supply with 8 AA batteries or 1 9V and 2 AAs.

[Paul Marossy]

The olcircuits.com people suggested moving the power rectifier/filter pcb away from the signal wires which means redoing all the wiring to that pcb with longer wires and moving it to the other end of the enclosure.  I would rather do a bunch of testing to rule other things out first before I do a bunch of desoldering and rewiring.

That's what I did when I made my Shaka Tube in a Hammond 1590BB. I kept the power supply as far away as I could from the rest of the circuit. No problems with hum at all.

[PRR]

> try twisting the heater wires together

It appears to be DC heat. Won't hum (ass-uming the DC is good and clean).

In the power supply: C1 100uFd is much smaller than I would spec. We have a 301mA load, we have a VAC similar to the desired "regulated" VDC, I would want much-more than 300uFd. I'd drop 1,000Fd (>25V) in there.

> which means redoing all the wiring

Sometimes building is like that.

Agree: if you can find a good 12V *DC* >300mA supply, even a motorcycle battery, try that instead of wart and little power-board. Be careful about polarity!!

[puretube]

Your AC input-jack carries a lot of humming current;
tightly twist the wires from that jack to the regulator-board,
and keep them as far away as possible from the tips of the IN/OUT jacks,
as well as from the tube-grid-circuit! (input-section)
and away from the stompswitch and its wiring...
And bend the twisted pair as close as possible to the (grounded !!! ) chassis...