Maestro S+H Problems. Incorrect Layout GGG?

[AlexK]

I think I'm going crazy looking at the Maestro S+H layout from GGG.  I searched through the archives and there were a couple posts saying that people have built this and it worked fine, but looking at the layout, the pinouts for the 741's look wrong to me.  On IC3, IC4, and IC5 (all 741 opamps) it looks like pins 6 and 7 are reversed.

I've traced out all the other pins and they look ok, but shouldn't pin 7 be to +9VDC and pin 6 the output?  Am I nuts?  The layout has them backwards.

My build isn't working and I'm pretty frustrated.

Can anyone confirm or deny this?

Thanks a lot,
Alex

[AlexK]

Wow, I'm an idiot.  I was naming the pins as 5 directly on the otherside of 1...instead of 8.  I have a small add-on board for Tonda's mods that I wired up wrong...the GGG layout looks right.   :oops:

Hopefully that'll clear things up.

-Alex

[soggybag]

Let me know if you figure anything out. I just finished wiring mine up this morning, and it didn't work. All I can here is a faint popping sound that varies with the rate of the speed pot. which I think is the famous LFO noise, that I've read is hard to get rid of.

I used the layout from uStomp. It lists LM833 as the opamps. Of which there are only 2 on the board. These must duals, I used TL072's which I had. I figure they should be similar.

[Ry]

Use the trimmers to dial in the effect.  You may have to also play with your noise source transistor to get it to work correctly.  I currently have a 2n2222 for mine.

Ry

[soggybag]

I'm not getting any sound at all, except for a faint popping which sounds like the LFO. The by pass works. What are the two trim pots for? Would misadjustment cause no sound to pass?
I had thought that if I could get the effect working in a basic way I could go back and audition transisters for noise.

[Zero the hero]

Which LFO?
When I've built mine, I had to set the trimmers carefully in order to make it work. And, as previously stated, the noise transistor plays a central role in this design. Socket it and try different transistors.
The layout is definitely correct, there are lots of build reports for this project.
If it keeps on not working, use an audio probe to see where the signal got lost.

[AlexK]

I got mine to work last night.  I had an opamp wired incorrectly (for Tonda's mods) and also a short on the board which took me a while to find.

The one thing that's bothering me is a fairly loud clicking noise while in bypass mode.  I'm true bypassing it w/ a 3PDT (LED also) and the clicking is pretty loud.  I'm not using a 1044 or anything like that, I just have 2 9VDC jacks and I'm powering it with a Voodoo Labs Pedal Power 2.

Does anyone know how I could get rid of this?  Is this the LFO noise you're talking about, soggy?  I didn't see any mention of this when I did a search.

Soggy, you should still get signal out with the trimmers in any position.  It seems like you want to trace out the main signal path as opposed to the side chains right now.  I would look at the pinout of the input buffer transistor and the 3080's.  Hope you get it to work.

Thanks a lot,
Alex

[soggybag]

I found problem with Q1. I'm using the uStomp layout. I'm not sure what transistor was used for Q1 in this layout, the part number it is not listed. I used a 2N5088 (TO-92). The pinout is EBC. Using the orientation shown on the layout (http://ustomp.com/files/b8dddef1-0000-00f5-852d-0a19181bbebb.gif) B and C are reversed.

After bending and repositioning the pins in Q1 I get sound with a little bit of the filter effect. In S & H mode I don't hear the effect but I do hear the signal mildly filtered. I have been playing with the trim pots and auditioning various NPNs that I have lying around.

Is there a method or procedure to setting the trimmers?

I had built a S&H into a modular synth. I remember the noise transistor had 30V (-15V, +15V) across E and C. Here I'm only measuring about 7V. Is this enough to get noise?

Thanks for the advice everyone. I will keep working at it.

[AlexK]

Soggy,

I read in another post that you want to set the 10k trim fully clockwise (this is the volume for the noise transistor) and put the 100k in the middle.  The 100k sets the nominal bias for the control pin of the 3080 I think which sets the nominal filter tone in S+H mode.  These trim pots only effect the S+H mode, not the filter mode.

I think you just want to tweak the 100k to where you want the tone.  The 10k needs to be set to get the best amount of noise.  Once you get a noisey device there, I found it was really easy to set it correctly.  If the 10k is set fully clockwise and you have a noisey device, you'll know it's working.  Then you can tweak from there.

-Alex