TS808 problem, no distortion (but gain works)

[chovi]

Hi, I built this one TS808 tube screamer
http://effectslayouts.blogspot.com/2015/02/ibanez-ts808-tube-screamer.html
my mods:
substituted 51pf to 47pf, 27nf to 22nf.
Sound is only clean, no distortion. I tried several op-amp 4885 (chinese) and sound is still clean. When i tried tl072 sound was a little bit distorted but still sounds clean. Drive pot appears as a second volume pot.

Checked all values resistor and caps (especially 47nf/4.7k checked OK), tried 1uf elect. caps replace to tantal, 220nf tantal too,  checked all solder joints/traces, replaced diodes, replaced transistors (2n3904 to 2n5088),  a500k pot and sound is still the same.
voltages:
Q1,2 (2n3904,2n5088) - C=9.10v B= 3.8v E=3.4v
pins 1-3= 4.5v, 4=0v 5-7=4.5v 8=9v
Diodes A 4.53v, C 4.53v

Battery 9.06v

hm...please can you help me?

[antonis]

Hi & Welcome..

Your voltage measurements look OK..

Could you plz post some pics of your build..??

[Keppy]

Are you hearing a ton of boost when you turn the drive up? If so, then your clipping diodes are bad or mis-connected.

If you're not hearing a ton of boost, then you might have the wrong value cap/resistor coming off of IC pin 2 (47nF/4.7kΩ), or the wrong/bad gain pot.

Another possibility is that the 51k feedback resistor is making contact with both sides of the gain pot. That would cause resistance in the feedback loop to be 0-51k instead of 51k-551k, giving you a gain from 0-10 instead of 10-100.

[iainpunk]

have you tried other diodes? which ones are in there? are they still good?
i bet its the diodes.

cheers, Iain

[chovi]

Thank you for advices.
I used 1n4148 diodes, tried replace new ones and still same problem.
checked (47nF/4.7kΩ) values/ solder joints, but its ok.
when i turn drive pot i hear boost, but its appears as boost volume. (distortion is low)

last chance, I will try to replace 51k.

please dont judge me for my soldering i am beginner a this is my 2nd project.

[duck_arse]

can you tell us the markings on the 47nF cap, please? it looks way too small, to me.

also, welcome.

[chovi]

473, i think this cap is OK

[ElectricDruid]

please dont judge me for my soldering i am beginner a this is my 2nd project.

I recommend you get a tip cleaner for your soldering iron and use it frequently. That black muck across the board shows me the tip is dirty, and that makes it very hard to make nice clean joints. Your builds will be more reliable and you'll do less debugging.

I used a dampened soldering sponge to clean the tip of my iron for years, but I've switched to the metal-wire-in-a-little-ball tip cleaner and I think it's much better because it doesn't cool the iron down. I recommend it. This type of thing:



(This is an expensive Hakko branded one, but there are lots of cheap alternatives)

[iainpunk]

get some cleaning alcohol/spiritus and an old toothbrush, and take off all the black gunk so we can actually see the state of the joints. use a good worn out toothbrush, they seem to do a better/quicker job at cleaning the gunk, idk why

those brass solder 'sponges' are amazing, i just put mine in a used airgun pellet tin with a skewer through two holes to keep the thing in place, it improves soldering experience so greatly, i went from having to debug 2 out of 3 boards to not having debugged my own boards for quite a few projects now, more than 10 that is...

cheers