Help with Rocket Fuzz, PLEEZ :) No worky

[lerxstlover]

Hi all,

Wondering if someone could help with the Rocket Fuzz.  I built it last nite and wired it with a 3PDT switch for true bypass and it works fine in bypass but not when the effect is turned on.  LED lights up and it has power, but no sound.  I've used my probe and am getting correct (I think) readings from everything, double-checked transistor pinouts, caps, etc.  I also checked all the solder points and made sure there were no bridges or gaps in the etching.

I recreated a PCB from the layout on R.G. Keen's website at http://www.geofex.com/PCB_layouts/Layouts/rocket.pdf.  I modified it a bit based on wiring it to a 3PDT (you will see in the pic I've posted) plus wiring in a 9V DC jack.

I accidentally discovered when testing with a probe that if I touch the top of R3 with the bottom of R10 (ref pic posted below) I get sound and it's a little fuzzy, so that would tell me that maybe there's something in between those two points that's not working right, but this is only my second pedal and I don't have the schematic so I don't really know what's "between" and what to look for.  On the other hand, since the original uses a 2PDT that can go to a Millennium and I "merged" a bypass with LED using a 3PDT switch, I'm thinking I might have gotten something wrong with the switch wiring.  I just finished the DOD 250 with bypass/LED so I used that wiring layout to attach the switch to this board based on offboard wiring layout #5 as posted on TonePad.com - http://www.tonepad.com/project.asp?id=35

Here's the pic of the wiring:



I figure first I'll make sure the wiring is good, then I guess it's back to the board.  Of course, I could have messed up something on the PCB.  I've checked that about 20 times against the original and I'm pretty sure I have it pretty much exact (except for the mods/ommissions, of course.)

All comments/suggestions appreciated!  Thanks in advance!

[Cardboard Tube Samurai]

This might help. Just looking quickly at your switch wiring it doesn't seem quite right. Here's a link to GGG's layout with 3PDT switching

http://www.generalguitargadgets.com/diagrams/rocket_lo.gif

Failing that... is it in a metal enclosure? I have found (found out the hard and frustrating way) with past builds that by using metal DC jacks in metal enclosures shorts the whole circuit

[lerxstlover]

Dangit!  I looked all over for a PCB layout and couldn't find one so started making my own....thanks for the tip.  I'll check it out right away!

That layout looks a tad different, but I'm sure I can match it up enough for the switch.  At least I got some experience with layout on a PCB 

[lerxstlover]

Well, I checked out the link you sent.  The PCB is a bit different, but the pot and switching is basically the same, just reversed.  I went ahead and reversed the wiring on my switch and still the same thing....fine in bypass but no sound in effect mode.  I just replaced a bunch of the components and retested them, so either my switch is bad (I'll try a new one) or I really messed something up on the board/layout.

[burnt fingers]

Please read the what to do when it doesn't work.  It will help you get the information to help us help you.

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Apart from actually being at your place inspecting the circuit board, the what to do whent it doesn't work thread will be the easiest way to get you up and running.

Scott

[lerxstlover]

Yeah, I had read that before getting started, but I guess I skipped over the last part   

Anyway, here goes:

Referring to the diagram posted previously:

Voltage at the circuit board end of the red battery lead = 9V
Voltage at the circuit board end of the black battery lead = The black battery lead does not go to the board, but to the ring of the stereo jack.  It says 0V.

Q1
C = 9V
B = 0V
E = 5.2V

Q2
C= 1.2V
B= 0V
E= 0V

Q3
C = 1.2V
B = 0V
E = 0V

C1 (I'll just say top and bottom on these)
top = 0V
bottom = 0V

C2
top = 0V
bottom = 5.2V

C3
top = 0V
bottom = 0V

C5
top = 7.2V
bottom = 9V

C6
left = 7.2V
right = 0V

C7
left = 0V
right = 0V

C9
top = 0V
bottom = 0V

These two are the electrolytic:
C4
+ = 9V
- = 0V

C8 (I replaced it today to be safe)
+ = 0V
- = 0V

R1
top = 9V
bottom = 0V

R2
top = 0V
bottom = 0V

R3
top = 0V
bottom = 0V

R4
top = 3.2V
bottom = 0V

R5
top = 9V
bottom = 1.2V

R6
top = 7.2V
bottom = 9V

R7
top = 7.2V
bottom = 1.2V

R8
top = 0V
bottom = 0V

R9
top = 0V
bottom = 0V

R10
top = 0V
bottom = 0V

I tried to scan a pic of the bottom of the board, but it kept coming out blurry.  I'll see if I can get a digital pic to post.  I'm thinking I just goofed up the traces on the PCB when I was trying to recreate it.  I checked again and don't see any broken traces or solder bridges and all the pins are soldered tight, so maybe I have some traces connecting to wrong components or something.  That was the first thing I checked but I'll go back and check again.  I printed out R.G.'s original and my render and checked each trace with a highlighter.

Thanks again!

[burnt fingers]

Those tranny voltages look off.  Double check your pinouts and connnections to the trannys.  I think the collectors should be biased at about half the supply voltage.   4-5 volts should be what you read. 

Scitt

[petemoore]

http://www.generalguitargadgets.com/diagrams/rocket_lo.gif
Q1 is an emitter follower / buffer
C = 9V ok
B = 0V  needs to be higher than base by it's diode drop
E = 5.2V [seems high for base or emitter, perhaps transistor pinout check and bias resistor value re-measures
  Q1
Q2
C= 1.2V
B= 0V  This base is not biased, needs to be .06v above emitter
E= 0V should be/is ground/0v in FF, correct
Q3
C = 1.2V should be 1/2v of supply v
B = 0V Base same as emitter, not biased
E = 0V   
  Q2 collector is to connect to, and = Q3Base voltage, miswire or misorientation here
  measuring every node to node...connections, resistances...
  it looks as though Q2 C and Q3C may be connected...or...somehow the translation to text... or transistor orientation...
  Counting connections at each node on the schematic, then DMM verifying that those connections and no 'extra' ones....like Q2 B/E reading the same voltage, and being adjacent one another, perhaps there is a solder bridge here, test whether they are connected using DMM Beep mode.

[Gus]

Look at the section around Q2 the emitter goes to the 100 ohm and then the base the 100 ohm  should go to ground.  Then you have the emitter of q2 going to the base of q3....... Look at the Q2 area

This is a top view of the PCB?

[R.G.]

Pete is absolutely correct - the transistor voltages indicate that this thing CAN'T be working. And he's fingered the issues.

Since you provided passive component voltages, we may be able to do more.

C1 top = 0V bottom = 0V

C1's bottom side needs to be up at the bias voltage of Q1's base. It's at 0V, as is the base. This can only happen one way - the impedance pulling it to ground is much lower than the impedance pulling it up. That could be a few things: it could be shorted to ground; the resistor pulling it down could be much, much smaller than the resistor pulling it up due to incorrect values; or the path to +9 through R1 could be open. An ohmmeter test with the power off to test the resistance from Q1 base to ground and +9V should tell you pretty quickly which it is.

There is another possibility - a measurement error. The emitter of Q1 is sitting suspiciously near the voltage it might need to be. If your voltmeter has a low input impedance, it will load down the base all by itself and could erroneously show a voltage too low. Or the point of the probe could have slipped.

How do I know these possibilities? Guess. 

On Q2, you ran into a trap I laid for a commercial builder that was stealing my stuff. At the time I put that up, there was a guy who was bringing out a !NEW! IMPROVED! pedal every time I put a PCB up. It stopped when I put up the Rocket. I was selling PCBs for effects back then, and the PCBs I sold had the correct layout, as did the documentation for the PCBs. The posted layout does not correspond to the schematic. It's obvious if you trace the schemo versus the PCB, but this guy never did that.

Sorry about that. I thought I'd pulled all the traps out, but apparently I missed this one.

I've now corrected it at GEO. There are two changes. The lower end of R9 should be, not connected to the base of Q2. On your PCB, unsolder the bottom end of R9 and run a wire from that end to the bottom end of R4, or drill a new hole right by the ground trace below R9 and bend R9's bottom lead a bit longer to reach ground. The second change is that Q3's base should connect to Q2's collector, not to its emitter. You can fix that by cutting the trace from Q2 emitter to Q3 base and soldering in a bit of bare wire from Q2C to Q3B.

The Q1 part was correct with the schemo, so you have a bug in there still. Try those fixes and the debug on Q1 and get back with us.

[lerxstlover]

SWEET, SWEET SUCCESS!

Thanks guys for your help.  R.G., I made the two corrections you proposed and voila!

I really like the sound of this pedal!  SUHWEET!

And I have NO PROBLEM hitting those traps you put in the layout.  I'd probably do the same if that happened to me.  I did check GEOFEX and it looks like the PCB under the FX Projects looks the same, though.  No prob, I'll update the layout I made with the changes.    It's just nice to know I'm not crazy! (but just inexperienced.....)

Thanks again!  Now on to the Omni Drive.....hehehe

[R.G.]

You may have to force a reload by punching the reload button you your browser. If the page is still in your browser cache, it won't reload it.

I checked, and the modified version shows up for me.

Again, sorry you ran into that.

[$uperpuma]

cheers on the traps   another way Sir R. G. Keen makes us learn.  And thieves are typically lazy and will take the path of least resistance... if he has to WORK to much at it... he'll skip it and move on...simple insurance.

[lerxstlover]

You may have to force a reload by punching the reload button you your browser. If the page is still in your browser cache, it won't reload it.

I checked, and the modified version shows up for me.

Again, sorry you ran into that.

Will do.  Thanks again.  You know, I drilled an enclosure and mounted everything and it quit working    So I took it out, thinking maybe I ground it out, but nope, still no sound in effect mode again.  I must have busted something while stuffing it into an enclosure.    Dangit.  Oh well, at least I've learned how to debug, so I'm off to work on it some more...I know it works, so just gotta find the bad spot.

[lerxstlover]

Hi All,

Well, it's back.  For some reason the Rocket quit working.  It worked fine after making the corrections from R.G. to the PCB, then I went and bought an enclosure, tested it again and then put it in the enclosure and it quit working.  Works fine in bypass but not in effect mode.

SO, I started to debug based upon my new found knowledge (thank you) and my meter quit working!  Replaced the battery, no good.  So now I have a fancy new digital meter and am posting the NEW readings below.

HOWEVER, I also built the signal trace thingy with the 1/4" jack and a .1 uF cap from GeoFex.com.  Works great!  I get a nice strong signal starting at signal in on the board (ref layout above) until I get to the left side of C6, then the sound is really low, barely audible.  Once you get past the tops of R7, R6 and C5, there is no sound.

Anyway, here are the new values:

Voltage at the circuit board end of the red battery lead = 9V

Q1
C = 8.84V
B = 4.38V
E = 5..06V

Q2
C= 1.31V
B= .68V
E= .08V

Q3
C = 7.01V
B = 1.31V
E = .75V

C1 (I'll just say top and bottom on these)
top = 0V
bottom = 4.38V

C2
top = 0V
bottom = 5.06V

C3
top = 0V
bottom = 4.8V

C5
top = 8.62V
bottom = 8.83V

C6
left = 8.62V
right = 0V

C7
left = 0V
right = 0V

C9
top = 0V
bottom = 0V

These two are the electrolytic:
C4
+ = 8.82V
- = 0V

C8
+ = .74V
- = 0V

R1
top = 8.82V
bottom = 4.37V

R2
top = 0V
bottom = 0V

R3
top = 4.37V
bottom = 0V

R4
top = 5.06V
bottom = 0V

R5
top = 8.82V
bottom = 1.3V

R6
top = 8.61V
bottom = 8.82V

R7
top = 8.61V
bottom = 6.98V

R8
top = .67V
bottom = .67V

R9
top = .08V
bottom = 0V

R10
top = .74V
bottom = .67V

I'm thinking that since I'm getting a weaker signal after C6 that it's something in that part of the circuit?  I'm going to go get some new caps and some sockets and start switching them out to see.  Thanks again!

[R.G.]

First let me say that you have the kind of approach that will make you a good troubleshooter. Good work!

You are absolutely correct - if the signal disappears near C6, then the trouble is near there.

Your results make me think that something on the right hand side of C6 is shorting to ground. Could be on the PCB, could be on the wiring to the tone pot. If the PCB had not worked already, I would suspect that C9 was shorted either by a solder problem or internally. But this has worked, and unless you damaged the PCB or C9 in boxing it up, I'd say that the wiring to the tone pot is suspect.

Does twiddling the tone pot make any difference? Or the volume pot?

[lerxstlover]

No diff wiggling any pot connections.  I checked all the solder connections.  I'm thinking it's a component problem.  I put the PCB under a magnifying glass and did not see any bridges or gaps, but now that I have a specific area to look in I'll go back at it.  I'll concentrate on the components around C6 (after replacing C6) and see what I can find.  If that doesn't work I'll replace the pots.  If that doesn't work I'll etch a new board and start over    When I did the layout I made it with a little more space between traces to avoid bridges until I get my solder skills (you know, skills....) so the board JUST fits in the enclosure.  I started compacting it when I updated the layout with the fixes to get it a little smaller.  Me thinks I'll invest in a bread board to prototype since I plan on getting into more complicated circuits.....heheh

Thanks again for the help.  I'll let you know what I find when I get back at it tonight.  I decided I should actually go to work today....

[lerxstlover]

Ok, I got it working again.  HOOORAY!!!!!!

Turns out, if you solder the pots backwards, the board won't work.....

Dang I gotta a) get used to looking "through" a board layout and b) quit working on these things at 3 am.....

Not I gotta little bit of a buzz when the effect is on but I know it's a ground somewhere so I'm happy.

Thanks again!  Now back to the office....