GGG Ross Comp -- Ready to blow brains out...

[camsna]

Still no go. Now I've REALLY tried everything. Well, obviously not, I guess -- since it still doesn't work. But everything I could think of, which I admit, is very little. Anyhow. Here's what's up now.

Replaced the 1k resistors with a 2k trimmer.
Replaced all the transistors with 2N5088s.

Now, I get signal...but only if the sustain and level controls are both DIMED! I double-checked my pots, they work and are of the right values and in the right places. So it's not that...but wouldn't it have been great if it were...

But I have some more data! I found some voltages taken off a Ross. Here are the working Ross voltages, compared to mine (RQx = Ross, MQx = Mine):

RQ1: E - 1.65v, B - 2.10v, C - 7.98v
MQ1: E - 2.39v, B - 2.97v, C - 6.84v

RQ2: E - 2.34v, B - 2.87v, C - 7.28v
MQ2: E - 2.37v, B - 2.93v, C - 6.87v

RQ3: E - 9.5v, B - 0v, C - 0v
MQ3: E - 9.2v, B - 0v, C - 0v

RQ3: E - 9.5v, B - 0v, C - 0v
MQ4: E - 9.2v, B - 0v, C - 0v

RQ5: E - 9.0v, B - 9.32v, C - 9.50v
MQ5: E - 8.7v, B - 9.20v, C - 9.24v

Now, slap me if I'm wrong...but they all look good 'cept Q1, right? Q2 is off, but it doesn't look like too bad -- the greatest difference is about .4v on the collector.

Also - here are the IC voltages from that same Ross and my build (pins 1 and 8 are unused).

R2: 4.92v
M2: 4.76

R3: 4.91v
M3: 4.76

R4: 0v
M4: 0v

R5: .633v
M5: .633v

R6: 2.76v
M6: 2.92v

R7: 9.5v
M7: 9.23

Looks good to me, but what do I know?

Also, here are some photos of the front and back sides of the board.



Lastly, here again are the links to the layout and schematic:

Schem:
http://www.generalguitargadgets.com/pdf/ggg_dnr_ross_sc.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Layout:
http://www.generalguitargadgets.com/pdf/ggg_dnr_ross_lo.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

What next? I feel like I'm getting SO close! But I'm plum OUT of ideas, save pull and replace every compoent one-at-a-time...

Thanks again, fellas!

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Cam

[camsna]

Is it so obvious that it's not worth telling me (like what my wife says when I don't know 'what's wrong')? Or have I stumped y'all, too?


I guess, what I really mean is....


Bump


Thanks again, guys. Hope you don't mind me bumping this.

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Cam

[small fish]

Well, it´s just a guess....but I would change all the tantal caps (especially the ones in the circles on the pcb) to electrolytic caps.
C6 needs to be polarized, the panasonic cap definetly isn´t.

Tell me, if I´m right...or wrong.... 

regards

[jkokura]

Good catch fish!

(see what I just did there...)

Yes, C6 looks like it's supposed to be polarized. The tants might be fine, but I like Electrolytics better soundwise in this circuit anyway.

Perhaps try changing C6 and see if that fixes things.

Jacob

[camsna]

Thanks, guys!

I subbed the tants because that's what Keeley uses in those positions and that's what my buddy wanted. He uses the non-polarized 1uf in C6 (as far as I can tell, based on a photograph and trace on FSB), too. But I'll swap it out for an electrolytic and see what it does

Just for the sake of understanding -- why willn't (generally -- theoretically...) non-polarized caps work in place of polarized? I'm happy to know THAT they won't, but would love to understand WHY they won't.

Thanks again, fellas! In due time, I'll be more of a contributor and less of a leach...


---
Cam

[jkokura]

Well, remember that the keeley one isn't necessarily the same schem... Whenever you build a project, you should rely on that schem and layout, not one for a different pedal.

Keeleyky likely uses the tantalum caps because of reliabilty reasons, not sonic ones. at least, if he claims sonic ones I'd like to see the data on the differences, cause I certainly don't buy that kind of stuff much.

Polarized caps are directional. How they operate is to release power in a specific way but only one direction. Non polarized caps go either way, so in some circumstances they can't always be used where a polarized caps are expected.

Don't know if that's the case here, but we'll find out soon.

Jacob

[camsna]

Thank you, sir! I appreciate your help!

Bummer is, though, that it didn't help. Replaced the poly cap with an electrolytic -- still no joy. What next?


(On another note. I think Keeley has a bit of an affinity for the tantalum caps. He considers them an 'upgrade' to some extent. I don't know why -- for reasons of reliability or some kind of phonic preference, but I decided to use them where he did for my buddy's sake. It's what he asked for )

Oh yeah, lastly, when I dime the SUS control, at the very end of the sweep it makes a 'woosh' sound, like when biasing a transistor. No idea how relevant that is, but thought I'd mention it.

Many thank yous!!!

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Cam

[jkokura]

Dude, don't know what to tell you.

You have the wrong value resistors in R4 and R3... You have 470R resistors there, and you should have 470K. That explains the wrong voltages on Q1 and that explains the bad results when trying to make the pedal work.

Check it out, you should get immediate results assuming that there's no other errors.

Jacob

[camsna]

Son. Of. A. Bee sting! That was it!!!

To top it all off, I made the mistake on TWO levels. First, I didn't read the resistor code correctly (but I'm not fully color-sighted). Second, when I measured those resistors before I put them in, they measured .470k, not .470m. But, I didn't read the measurements correctly.

Dang! SO glad it's fixed!!!

Thanks, guys!!!!!!!! It sounds GREAT!

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Cam

[jkokura]

Let this be a good (and gentle) lesson to ALL of you guys out there debugging. It is VERY important to follow the suggestions in the "How to debug" tips found here in the sticky. Checking parts is easy to skip over because we all assume we did it right. It's the easiest mistake to make, and what's worse is that we all often rely on the places we buy these parts from to get the value you right on the packaging. Even in this case, when the guy building it still has spent time double checking his part values BEFORE installation, there was still a mistake made.

Really, don't assume your parts are right. The first step of debugging should ALWAYS be the double and triple checking that all the right parts are in place. Get a friend or spouse to help you read the codes, measure them, and then measure them again. It never hurts to check again, and you know what happens when you assume you got it right.

Great that it's working. I'll get off my soapbox now...

Jacob

[jball85]

This may not be relevant, but on my last project (Egodriver) I finished and did not have any output. Before I S$#t a brick I pulled the shaft out on each pot (as if to clean) and found that my gain pot was faulty. I took it apart and found that the two tabs that are supposed to scrape the inner circle werent touching unless the shaft was pulled out. IE, Check your your pots.

[bigmufffuzzwizz]

Good job Jacob! Thats a catch! Good to see your builds working! I always check the resistors, and use the color code as a guideline.

This may not be relevant, but on my last project (Egodriver) I finished and did not have any output. Before I S$#t a brick I pulled the shaft out on each pot (as if to clean) and found that my gain pot was faulty. I took it apart and found that the two tabs that are supposed to scrape the inner circle werent touching unless the shaft was pulled out. IE, Check your your pots.

You can test it with a ohm-meter. Touch lug 1 and lug 3 for full resistance. Then from lug 2 to lug 1 turn the pot, it should go from 0 to the value. Do the same for lug 2 to lug 3.