Having trouble with a fuzzdog mucky hush

[verymodernworld]

I'm getting no sound between Q1 and R15 with a probe, getting readings of 0V with multimeter after R18 (which is reading correctly as 47R) - Does anyone know what I should look for next?

[GibsonGM]

Hi Modern, welcome!

There's a lot between Q1 and the output   Can you post a pic of the back of the board, and any input/output jacks you might have connected?

Have you used your DMM to test for voltage along the power rail to each Q, referenced to ground?   That would be next I believe.

Show everything you got in a pic, we'll get it going...

[verymodernworld]

Thanks for your response! I've been using the test setup recommended by Fuzzdog (which has worked on my other fuzzdog builds)

I checked my grounds - I set the DMM to test for continuity with the ground on the ribbon and got a beep from all the connections that should ground (I'm pretty sure that's what I'm meant to do - I've built nearly 10 pedals now, but this one has been the first where I've not been able to google myself out of trouble!)

[GibsonGM]

Great! Your work looks clean (that's a compliment).  Can you also post your build documentation or a link to them (the instructions you got)? 

I don't know 'the Fuzzdog test setup' but someone else reading this might.  What I hope to find in the instructions is info about how the power is switched....I can't tell but, it seems like you don't have a stereo jack for input ground switching but we'll worry about that later after we find out more about this guy you built.
Need to see what they intended.

I'd like to know if we have 9 volts going to the board when the cords are plugged in - if you know how, please do feel free to try to measure that
(do you?)  If not, give us what you have for info and await instructions...careful when you move that thing around to not bugger up the pot legs, they can snap off...

This is all just an 'info game', getting enough to point you in the right direction.

[bluebunny]

Here's the documentation.

[antonis]

getting readings of 0V with multimeter after R18 (which is reading correctly as 47R) - Does anyone know what I should look for next?

Before R18..

Placing DMM after R18 results into R18 + DMM's impedance shunting power supply..
Taling into account DMM's high impedance, you should read +9V (or whatever is your power supply with negligible voltage drop)

[duck_arse]

also welcome.

fuzzdog ought to get a kick up the arse for their circuit diagrams without part values on, and that tiny tiny tiny font for part numbers. which way have you fitted D1? it should have the bar-marked kathode down as you have it fitted, otherwise it will be shorting supply to ground. what jfet part numbers have you used? can we see any voltage measures at all?

[verymodernworld]

Thanks all for your responses!

Sorry, by 'fuzzdog test setup' I meant the SIL connector soldered to jacks and 9V battery connector in the picture.

I got about 8.08V from my battery, 7.11V before R18 and 0V from after R18 onwards.

I checked Q2, Q3, Q5, Q6, R4, R12 for continuity with ground and got beeps from the circled leads, and when I checked them for resistance it was normally between 0 and 3 ohms, mostly less than 1 ohm

Edit to add, on the tested transistors I got continuity beeps from the Drain lead and not from Source or Gate (which is what I think I want, given the schematic)

[antonis]

Don't go anywhere further than R18 issue..

P.S.
Let your battery rest in peace..

[verymodernworld]

To add - I have the striped end of the diode down, and the JFETs are the supplied 2N5457s

I've found a 9V battery with a bit more juice (8.65V), but it's still not passing R18 (it's about 11mV straight afterwards)

[bluebunny]

Try resoldering R18.  If it really measures as 47R, then we'll assume it's good.  In which case, it's not soldered in.  Or else the track or pad is somehow damaged.  Do you have a close-up of the back of the board where R18 lives?  As Antonis says, until you get that sorted, you'll get silence from the yellow region you've circled.

[verymodernworld]

I've circled R18's leads in red, and I tested for continuity between the leads (not the pads) on R18 and R4 and got a beep where I should

[verymodernworld]

I should probably clarify that where I'm getting sound after R15 it's with the probe plugged into the guitar's output jack and then the out jack from the test rig going to the amp

[GibsonGM]

Not sure what you're doing, Modern...if you're doing the 'test the board' step in the doc, it's guitar to IN, OUT to amp.   

If you have an AUDIO PROBE (can be found by searching on here or search engine), you connect that to the amp and a ground clip to the PCB ground.  You'd use a guitar or other sound source connected to the input to make noise to listen for along the signal path. 

At this point I think you should use your DMM to find out if you have ~9V on the power rail of the PCB...NOT continuity, but "DC volts" setting on your meter.  Black probe goes to ground (battery 'minus' or the pad GND on the board), use red probe to find voltage  between R18/R4,  top of R12...careful not to touch the meter probe across multiple places and cause a short....

[duck_arse]

all very interesting. if the 47R was shorting to ground, with 7 volts across would be over 1 Watt dissipation, hot and smokey. is the 9V battery reading 8V08 at the battery terminals when connected to the circuit, and the circuit is reading 7V11?

if you power off and measure the resistance (NOT continuity) between either end of the 47R and ground what do you read?

[verymodernworld]

So with some help from a reddit user I had identified the problem as Q4, but when trying to desolder it without taking the PCB mounted pots off I melted a couple of components and abandoned it in despair.

I had most of the components for the tagboard effects DLS Mk3 in my bits box and decided to build one of those instead - made the decal in a rush after work one evening and mislabelled the external mount presence control as contour though!

I used the 1590B enclosure I drilled for the Fuzzdog for an OCD clone

I have all the bits I need for another run at the Fuzzdog in my bits box and I will at some point, but for now I've got a functioning DLS clone and other pedals on my to-do list.

Thanks to all here for your help!

Tom