Guyatone Fuzz Monster Clone Debugging

[imJonWain]

Hey all, first post as I guest on here usually and hang out on I<3Fuzz...  I built one of Dino and Toecutters' Guyatone Fuzz monster clones on their PCB and am having some issues.  I followed parts and instruction dead on per the BOM except the SPDT switch is 2 position not 3 position center off, so some boost is always on until I get the right switch and I just placed the "tube LED" on the pcb as I don't care for the fake tube glow.  

Project BOM/instructions...
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=51479&g2_GALLERYSID=79e187f252ebd2ed24b187dab8d74d90

Bigger schematic..
http://www.diystompboxes.com/smfforum/index.php?topic=107281.0


The Issue...

So the pedal powers up and on single notes noodling it sounds good, like great, but with a bit of volume drop/flucuation when notes are played.  However if I bang out power chords or even full chords rapidly the sound quickly fades/fizzles to farty-sputters and takes a few seconds not playing to fade back up to normal, especially quick with low notes.  The issue is much quicker to appear with my Les Paul bridge and Telecaster then with my Strat which has rather low output pickups comparatively.

I checked the polarity on all the caps and they are correct, all the resistors I checked values as I installed.  I tried another tube just in case and it makes no differences, also tried different amps and guitars, same issue.

Only other note, that I don't think could have fried anything, is the first tube I used was actually DOA as the heaters just glowed like crazy on power up and the only output was insane screeching... Tried it in another pedal with same results


Voltages...

   IC A
Pin 1 = 5.91 V
Pin 2 = 5.91 V
Pin 3 = 5.65 V
Pin 4 = 0 V
Pin 5 = 5.90 V
Pin 6 = 5.90 V
Pin 7 = 5.90 V
Pin 8 = 11.80 V

   IC B
Pin 1 = 5.91 V
Pin 2 = 5.90 V
Pin 3 = 5.90 V
Pin 4 = 0 V
Pin 5 = 5.91 V
Pin 6 = 5.90 V
Pin 7 = 5.88 V
Pin 8 = 11.80 V

   IC C
Pin 1 = 5.90 V
Pin 2 = 5.90 V
Pin 3 = 5.91 V
Pin 4 = 0 V
Pin 5 = 5.91 V
Pin 6 = 5.92 V
Pin 7 = 5.90 V
Pin 8 = 11.80 V

BR1:
input= 12.9 VAC
output= 15.41 VDC

U1:
Pin 1 = 15.47 V (In)
Pin 2 = 0 V      (ground)
Pin 3 = 11.80 V   (Out)

D5:
A= -.63 V
K= 114 mV

D6:
A= 280 mV
K= 7.5 V


D7:
A= -.65 V
K= 114 mV

LED1
A= -0.45 V
K= 0V

LED2
A= 0 V
K= -0.45 V

LED3
A= 11.80 V
K= 10.10 V

Q1
S= 1.98 V
G= 0 V
D= 2.36 V

Q2
S= 9.3 V
G= 1.7 V
D= -2.48 V

Q3
S= 11.33 V
G= 10 mV
D=.45 V

Q4
S= 5.88 V
G= -100mV
D= 5.88 V

Q5
S= 5.68 V
G= 68 mV
D= 5.77 V

Q6
S= 5.9 V
G= 70 MV
D= 1.7 V

Q7
E= 0
B= .67 V
C= 100mV


Valve1
Pin 1 = 5.02 V
Pin 2 = -100 mV
Pin 3 = 0 V
Pin 4 = 0 V
Pin 5 = 11.79 V
Pin 6 = 9.04 V
Pin 7 = -280 mV
Pin 8 = 0 V
Pin 9 = 5.92 V

Note picture is before I moved the tube LED to the board and before I added LED3...

[digi2t]

Q7 is not a fet, but a transistor, 2SC1815. The build doc has the correct schematic, whereas the one you link to (bigger schematic) is incorrect.

Is Q7 correct on your board? Kind of hard to tell from the picture.

[imJonWain]

Pretty sure, it''s def not a FET, it's the 2SC1815-GR from small bear as specified , facing the same way as the shape on the board (flat side facing stomp switch area), I can double check in the AM but it's hard to zoom in on the BOM schematic. 

[UKToecutter]

you can fully omit the tube led if you don't want to use it rather than having it on the board, no point in wasting power.
It has no interaction with the circuit.

What rating is your 12VAC power brick?

[digi2t]

Been kind of swamped of late, but when I have a moment, I'll crack open the original unit, and take voltages.

[imJonWain]

cool I'll pop it out then, wanted to make sure it wasn't something silly going on...my PS is labeled as 1000ma, it's a generic brand one.  I'll mess with it some more tonight and try and get a higher res photo of the board with my camera just in case.

[imJonWain]

[Mustachio]

Hey Jon your latest pictures don't show up. I believe they are not marked public in the googles.

[imJonWain]

Fixed I think...

[UKToecutter]

Fixed how?

[UKToecutter]

Oh, did you mean the pictures were fixed or the board?

[digi2t]

Q2 and Q3 don't look right. Instead of the "GR" designation (as like the others), one is O and the other is R. Bizarre.

I believe that all fet's spec'd are supposed to be 2SK30A-Y, right? If you're using 2SK30A-GR, or R, or O for that matter, or worse, mixing grades, then that might create problems.

It might not need fet matching on the order of a phaser, but I'm thinking that they should at the very least all be inside the same drain current range.

[imJonWain]

I meant the pictures not working, probably shoulda said that haha.  

I hadn't even thought of the FET matching, good call....Yeah 2SK30A-Y is spec'd,  I just ordered the 2sk30's from smallbear and that's what I got, so I went with it since I couldn't find any spec sheets for the designations.  I gotta put another Mouser order in soon do you think I should just order the 2N5485's they have and use those?  Is it worth seeing if smallbear would sort through their lot for me to find 2 GRs or 6 Ys?    


http://www.datasheetarchive.com/dlmain/Datasheets-115/DSAP00975.pdf

According to that sheet the "R" 2sk30 drain current is a lot lower then the "Y" and way lower then the "GR" 

[digi2t]

I think 2N5484 might be closer to the 2SK30A-Y than the 2N5485.

Hopefully, someone with more brains on this issue will chirp in here. I tend to follow the "the original uses this, so...." train of thought. Especially when it comes to things that are above my pay grade. 

Andy, what did you use in yours? It sounds fine in your video.

[UKToecutter]

2SK30AY I think.
Lemme check.....

[UKToecutter]

Yep
2SK30A-Y
Got them from the fleabay
Am I allowed to say who I got them from?

[digi2t]

Yep
2SK30A-Y
Got them from the fleabay
Am I allowed to say who I got them from?

Information is power my friend. If they supply good parts to our membership, I don't see why not. Of course, Aron has the last word. If we're in the wrong, he'll let us know.

[italianguy63]

Sorry-- I have a related question.  Maybe you can help.

I got some 2SK30A's at the water festival.

Mine are marked K30A, and below that LH

Is the Y designation of big importance?  I assume these are "L" or "left handed."

MC

[Mustachio]

I stumbled upon this thread yesterday with a bit of info on the 2sk30's

http://www.diystompboxes.com/smfforum/index.php?topic=85270.0

[italianguy63]

Sooooo... "LH" is what color?!    

The water festival people say this on their site:

Manufacturer: TOSHIBA
Manufacturer Part No: 2SK30ATM-Y