BYOC Classic Compressor just farts

[Elysiumfx]

Yep. As the title says! Haha. What have I done?!?! I've used the modern components rather than the vintage upgrade... and I have signal! But..... it sounds like... well.... A lower octave, distorted fart. To be honest. I've slowly played with the trimpot but it's low level until the sweet spot and just noise from there. Perhaps a faulty 3080? I've reflowed everything. And everything seems to test as it should (my limited knowledge) but it sounds awful. Any insight? Google hasn't helped at all. Thanks in advance.

[stonerbox]

Voltages, voltages and voltages.

[duck_arse]

to paraphrase stonerbox: photos, photos and photos.

and to paraphrase antonis: circuit, circuit and layout.

[Kevin Mitchell]

I guess you can name it Frank & Beans.

Do the results change when you lower the guitar's volume?
What transistors are you using?

Feel free to post images. I suspect a short around the first transistor, if not a bad 3080.

Here's the build doc for anynone else chiming it.

[PRR]

> Perhaps a faulty 3080?

If you have to ask.....

[ElectricDruid]

> Perhaps a faulty 3080?

If you have to ask.....

I don't agree. While it's possible, there's ten other likely things to check first. Well, ok, I suppose the *actual order* of checking doesn't matter, but there's at least ten other likely things!

Many times people just assume their chips are faulty because they've seen loads of stuff online about fakes and dodgy chips and etcetc, but in reality, they've ignored a far greater quantity of stuff online about all the pedals that got fixed by resoldering the 3PDT correctly, or making sure the power was working, or not getting the tip and sleeve connections on the jack back-to-front or whatever.

[Mark Hammer]

Not looking at any schematic at the moment, but it is worth noting that often signal will not pass a misoriented (i.e., + where - should be) electrolytic cap unless you pick VERY hard.  In that spirit, check to verify all your electros are oriented properly.

And are you absolutely sure you didn't get one of these by accident? https://www.kickstarter.com/projects/stevegadlin/the-fart-pedal

[Kevin Mitchell]

Guys, that's why I suggested a short near the first transistor section. Or even a bad choice of transistor (or passive). If the signal isn't getting oversaturated before the OTA then the OTA is likely going to be the problem. I say this from experience as I've had a gassy OTA myself.

While we would like to dismiss these parts being the issue it's not impossible for them to be damaged. But we should dance around it until it's clear - which is of the wise. I mean, all we can do is dance around until more info is unveiled.

> Perhaps a faulty 3080?

If you have to ask.....

........

[ElectricDruid]

Sure, if you've got another '3080 handy from a different order (different seller, whatever) handy, then bang it in and see if it all springs to life. I know I would. But many people aren't in that situation, and don't have a known-good chip hanging about.

+1 what Kevin said.
I don't want to dismiss the '3080 as being the potential cause of the problem, just say that there's some other cheaper, easier things we can try first before we recommend to the OP that they go and buy another chip - as you say Kevin, "dance around it until it's clear". Good advice.

[PRR]

> Perhaps a faulty 3080?

If you have to ask.....

I don't agree. While it's possible, there's ten other likely things to check first. ..... Many times people just assume their chips are faulty because they've seen loads of stuff online about ....

Chips in general, NO, they are never your first suspects, even if the interweb vilifies them.

But the '3080 specifically has been very suspect for most of this century. They had not been made since 1990? There were years of back-stock, but those parts are gone. Outright fakes dominated the market for years more. Recently Bear and Rochester have re-run '3080 masks. But re-marked LM358 are far cheaper and more available. So I want to hear where any such project got its '3080.

[Elysiumfx]

Hi all, Thanks for your help. I had to take the day off yesterday - 1. because life happened & 2. My brain was mush! Ok so before I start looking back over the replies:

Voltage on the IC

1 - 0v
2 - 2v
3 - 2v
4 - 0
5 - 4v
6 - 0.1
7 - 6.3v
8 - 0v

Ha... this definitely doesn't look right. I'm back on it today so I'll let you know further findings. I'll try and upload a photo later, but I've soldered and desoldered way too much for this to be viable anymore - it's now becoming a personal vendetta to just get close to the correct sound.

Thanks as always.

Dave

[Elysiumfx]

I'm now trawling through my receipts to see where I sourced the 3080. I know that I was buying a LOT of parts at the time, and so there is every chance that it is from eBay - added to another order. Most of my stuff comes from verified eBay dealers... but not necessarily this.

[Elysiumfx]

Here's the schematic

[Elysiumfx]

And just before I sit down and start the next debug process: guitar goes in - I get very little signal with FX on. Although farts when I hit the strings very hard. Just tested a FM radio output through it while I was testing voltages... I get signal. Boosted and heavily distorted signal.

[fowl]

There's an error in that schematic, C5 is backwards.  It's not your main issue though.

You say BYOC and I think of a kit.  I've built a few from them years ago and had no problems with the parts supplied.  But if you got CA3080s from Ebay, there's probably a greater chance of them being fake than real.

[ElectricDruid]

Chips in general, NO, they are never your first suspects, even if the interweb vilifies them.

But the '3080 specifically has been very suspect for most of this century. They had not been made since 1990? There were years of back-stock, but those parts are gone. Outright fakes dominated the market for years more. Recently Bear and Rochester have re-run '3080 masks. But re-marked LM358 are far cheaper and more available. So I want to hear where any such project got its '3080.

Yeah, fair points. The 3080 is certainly more often a source of "fake chip" problems than a lot of other things.

[Elysiumfx]

I've spent the day looking through x3 reading glasses and I can't spot any issues. I've checked all the solder joints again, and reflowed a few suspects. Each time I am getting exactly the same result. Took a break - tested my 2nd chorus clone (that didn't work either, problem with the 4047) so I'm going to stop for today and order a couple of 3080's from a reputable dealer. I'll come back to this next week. Thanks for all your help, when I have a known working chip, I'll start debugging again if necessary. But for now, I'll blame the IC and take a break.

I've been on a pedal build mission over the last few weeks and I'm now on the ones that are being difficult! 11 working, 3 non working (compressor and two chorus) and 4 unfinished (distortion, vibrato, m man delay and a fuzz). So I'll take that as not bad and end the week here. 

Thanks again.

Dave

[PRR]

5 - 4v

Iabc pin, pin 5, is one diode/transistor junction drop above the negative rail. Or should be. Say 0.5V to 0.7V depending how hard you drive it. It can be as much as 0.75V in a room, 0.9V when it is cold enough that the brass monkey's balls crack and fall-off from cold (-55C).

4V on pin 5 is either blown beyond redemption or was never a diode/transistor junction.

I do wonder how pin 7 (V+) can be 6.3v from a 9V battery. However the '3080 will work on low voltage, and pin 5 still can't be >1V.

[Elysiumfx]

For those of you interested in a follow up - new authorised CA3080 arrived today from my usual guy. Switched it out. Worked first time.

Thank you for all your help - Note to self **do not buy chips on eBay!*

Dave