Slow Gear debug

[MmmPedals]

Built a slow gear from Genera guitar gadgets layout. etched my own board. only sub was 2n5088 for the bc549's. all hfe of 507-509. double checked all the orientations of caps and trannies.
I get a very weak signal with none of the desired effect. there is some tremelo like throbbing.
The voltages are jumping around (which explains the throbbing) at the following places. on the
IC (tl071) at pins 3,6,7.
T1 at the base
T2 at the gate
T4 All pins
T5 All pins
The vlotages line up to another build report i searched out on the forum exept T4 and T5 was a little lower. Again they are constantly fluctuating.
Any idea what could cause this? Its not supposed to jump around like that is it?

[Govmnt_Lacky]

You didn't mention it so I figured I would add this. Did you read the Build notes for the Slow Gear on JDs site? It talks about orientation of the 5088/3904 and also talks about being specific about using a 2SK30A for T2. Just wanted to throw that out there.

Good Luck. Posting voltages might help. Even if they are "throbbing."

[Govmnt_Lacky]

Here is the Service Notes for the SG-1. May help you "tune" this one once you get it working.

http://files.effectsdatabase.com/docs/schematics/boss_sg-1_servicenotes_001.gif

[MmmPedals]

I did orient the 2n5088 correctly.
I would like to make sure the voltage should be varying before i kill myself trying to set the trim.
At this point The pedal is not the only thing throbbing. 

[Govmnt_Lacky]

Looks to me (according to the GGG schematic) that Pin 7 is tied to V+ via a few resistors. Does not indicate to me that it should be "throbbing." Looks like it should be a little less than battery voltage constant. Might want to remove the TL071 (if you used a socket) and try reading voltages on the empty pins at 3, 6, and 7. Might lead you to a bad component or solder joint.

P.S. I am, by no means, an EE so someone may chime in and give you better advise however, looks pretty obvious that it should NOT be throbbing at pin 7.

[Skruffyhound]

I just built one a couple of days ago without the 2SK30A, and it works well (sorry!). Somewhat to my surprise, since I read that alot of people (Slacker and Solderman for instance) had given up on this one, "the only effect I never got working" etc.

If you don't find the solder bridge soon PM me and I'll take some voltages for you.

The only thing I would like to improve with my build is the sensitivity of the trigger. I find I have to readjust sensitivity depending on whether I play on the top three strings or the bottom three. The input is that delicate. Balancing that out would make this a very useable effect, also in relation to chords.
Good Luck

[MmmPedals]

I desoldered the IC and the varying voltages stopped. Put in a socket and a new tl071 and it back. 

[Govmnt_Lacky]

OK. You say that the voltage is oscillating. What is the "range" of the oscillations? Also, you may want to break out the magnifying glass and inspect for solder joints.

Did you use the 2SK30A or another FET?

[MmmPedals]

  Found a hair thin piece of copper that didnt etch. Must have been a smudge from the printer because i forgot this board in the acid for like an hour.
Anyway works great now. thanks for the help.

[Skruffyhound]

Great!
Which FET did you use?
Could you let me know what the sense control is like on yours, I'm considering some mods for mine before I will be completely satisfied, but I don't really know if the behavior I'm experiencing is "normal".

[wavley]

Thanks for those service notes!  I built one and it works great, I didn't use the SK either, I didn't think it was as smooth.

[Skruffyhound]

I'd love to hear what you think about the sensitivity on yours and which FET you ended up using Wavley. I used a 2N5245 that I'd pulled out of an old Bang and Olufsen unit a while back. B and O at least during the 80's were kind enough to tape a full schem and annotated parts list inside their gear so I often pick odd stuff I'm missing out from there. I had reasonable success with other FETs, but that one was the best.

[MmmPedals]

I used an sk30.
The sensitivity control, controls how strong of a signal you need to open the gate. If you're using something to boost your signal before the SG you will need to turn down the sens control. Or depending on the output of your PU.
It does have some effect on the effect because with the control turned up the gate will open easier and feel less like a swell.

[Galego]

I finished mine yesterday. Used BC549 and a 2SK30A. I had a couple of very closely matched BC549's that i put aside for the build. But that was a month ago. When i started to solder everything, i opened the bag and thought, "why the hell are these in a separate bag?" and just soldered them regardless. 

Only when everything was assembled i went through my notes and remembered they should be matched. Even with them unmatched it worked right away. It was a bit rough and had a bit of throbbing as the sound faded. I swapped the BC549's for a matched pair and figured out how to tune the trimmer to make it work properly. I still need to compare it to the SG patch in my Roland GP-100 to hear if it works as it should, but seems fine.

[Skruffyhound]

Yeah, like I say above, I understand the function of the sense. knob, but if I set it to work well with the lower strings (EAD) then the upper strings (GBE) have to be picked increasingly hard for the effect to trigger until I reach half way up the neck on top E where it's impossible to pick any harder
The upper strings just aren't producing enough AC voltage to trigger. I just wondered if anyone else had experienced this or it was particular to my build.
It's like the envelope covers most but not all of the neck, I can tune to get good effect anywhere on the neck but not everywhere at the same time. Hope I explained it better this time.

[wavley]

Yeah, like I say above, I understand the function of the sense. knob, but if I set it to work well with the lower strings (EAD) then the upper strings (GBE) have to be picked increasingly hard for the effect to trigger until I reach half way up the neck on top E where it's impossible to pick any harder
The upper strings just aren't producing enough AC voltage to trigger. I just wondered if anyone else had experienced this or it was particular to my build.
It's like the envelope covers most but not all of the neck, I can tune to get good effect anywhere on the neck but not everywhere at the same time. Hope I explained it better this time.

I find that running a compressor before my slow gear smooths all the swells out very nicely.

[Skruffyhound]

Thanks for that.
Which compressor are you using?

[wavley]

MXR Super Comp, it's pretty decent, I don't really use compression much.  In front of the slow gear and when I go all Don Caballero tapping is about it.

[MmmPedals]

Yeah, like I say above, I understand the function of the sense. knob, but if I set it to work well with the lower strings (EAD) then the upper strings (GBE) have to be picked increasingly hard for the effect to trigger until I reach half way up the neck on top E where it's impossible to pick any harder
The upper strings just aren't producing enough AC voltage to trigger. I just wondered if anyone else had experienced this or it was particular to my build.
It's like the envelope covers most but not all of the neck, I can tune to get good effect anywhere on the neck but not everywhere at the same time. Hope I explained it better this time.

Maybe your PU are not balanced. Raise the trble side of your PU untill the volume of bass and treble strings are balanced.

[Galego]

Yeah, like I say above, I understand the function of the sense. knob, but if I set it to work well with the lower strings (EAD) then the upper strings (GBE) have to be picked increasingly hard for the effect to trigger until I reach half way up the neck on top E where it's impossible to pick any harder
The upper strings just aren't producing enough AC voltage to trigger. I just wondered if anyone else had experienced this or it was particular to my build.
It's like the envelope covers most but not all of the neck, I can tune to get good effect anywhere on the neck but not everywhere at the same time. Hope I explained it better this time.

Yeah, that happens to me too.