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I violated my tube screamer and now need someone to save my ass

Started by Obie bong kanobie, May 29, 2016, 06:25:21 AM

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Obie bong kanobie

Ok so I'm an idiot, I have worked with vero and built my first two pedals and then went to mod my tube screamer 💡 Great idea in concept except I held my iron to the pad for to long and lifted part of the trace. It's the 4.7k  resistor and 20nf input cap. Looks to my newbie eyes that it's the VR section of each component that got lifted. There connected on the underside so that's how I managed to kill two birds with one stone.  If anyone knows what else I can point to point wire them to I'd be really grateful.  Or the easiest way to fix my mistake.  I'm trying to go through the schematic and fine components I could but it's hard for me I think the 4.7 k can be connected to the 510k resistor(if it's close enough) because it also goes to VR. or I'm I sadly mistaken about how to fix it. I'll attach a picture and I appreciate anyone who takes the time out of there day to post suggestions

Obie bong kanobie

#1




m-Kresol

Hi,
if it is truely the 4k7 that goes towards the clipping diodes than connecting it to the 510k will work. Just make sure with a multimeter to check which side of the 510k goes to Vr (should be around 4.5V) and then use a piece of wire to connect the pads. Check with the continuity setting that they are well connected afterwards.
However, I don't see how the 20nF input cap should be tied with this 4k7 resistor or to Vr. There is still the 1k and 510k resistors in between. Are you sure it's that cap?
I build pedals to hide my lousy playing.

My projects are labeled Quantum Effects. My shared OSH park projects: https://oshpark.com/profiles/m-Kresol
My build docs and tutorials

Obie bong kanobie

#3
Ok so your right it's the 47nf cap not the 20nf cap.  So if anyone can think of a good place to connect it to as well it would help tons. I found a very useful page and here's a pic that will help tons.  I just want to here from someone more experienced it's all good before I turn on my soldering iron again


Sorry for all the pictures


m-Kresol

that pic helps a lot. It will be an easy fix, assuming you did not lift any other pads. do the following:

*) solder one leg of the 4k7 resistor to the Vr connection (the trace connecting to the pin marked '13')
*) solder one leg of the 47nF cap to the non-lifted pad it was attached to before (the one below the '10' pin)
*) bend the free legs of the resistor and cap towards each other (you can poke both trough the lifted pads and do this on the bottom of the board) and solder them together.
*) You're Done! The trace doesn't connect to anything else, so that's it.

I don't know what you did want to do by desoldering these parts, but this would be the 'back-to-stock-version' option.

Hope the instructions are clear. If not, I'll highlight the pads in question.
I build pedals to hide my lousy playing.

My projects are labeled Quantum Effects. My shared OSH park projects: https://oshpark.com/profiles/m-Kresol
My build docs and tutorials

Leevibe

And don't feel bad about lifting pads and traces on a production PCB. it's really easy to do, and it's usually pretty easy to fix.  Hang with it and let us know how it goes.

Obie bong kanobie

#6
Amazing thanks so much guys. I actually wasn't going to use the stock values but just wanted to refer to them by there original part value     That resistor I'm dropping to 2.2k and that 20nf cap is going to be a 100nf  (cliche I know). Also planned on swapping out the input transistor for a ultra low noise mpsa18 and also swap the 51pf for a 51pf silver mica. I know it won't make much of a difference but it's more then tiny bit of noise it'll help with as well    Bat41 /1n4148 asymmetrical clipping as well
   Seriously thanks so much for the help and I'll post pics when I get home and le you know if everything goes well.   I already did all of those mods except I have to change the 20nf cap to 100nf and also switch the 47 nf cap back because I switched the wrong one thinking that was the input cap

Quote from: m-Kresol on May 29, 2016, 09:53:31 AM
that pic helps a lot. It will be an easy fix, assuming you did not lift any other pads. do the following:

*) solder one leg of the 4k7 resistor to the Vr connection (the trace connecting to the pin marked '13')
*) solder one leg of the 47nF cap to the non-lifted pad it was attached to before (the one below the '10' pin)
*) bend the free legs of the resistor and cap towards each other (you can poke both trough the lifted pads and do this on the bottom of the board) and solder them together.
*) You're Done! The trace doesn't connect to anything else, so that's it.

I don't know what you did want to do by desoldering these parts, but this would be the 'back-to-stock-version' option.

Hope the instructions are clear. If not, I'll highlight the pads in question.

Leevibe

Quote from: Obie bong kanobie on May 29, 2016, 04:25:22 PM
Amazing thanks so much guys. I actually wasn't going to use the stock values but just wanted to refer to them by there original part value     That resistor I'm dropping to 2.2k and that 20nf cap is going to be a 100nf  (cliche I know). Also planned on swapping out the input transistor for a ultra low noise mpsa18 and also swap the 51pf for a 51pf silver mica. I know it won't make much of a difference but it's more then tiny bit of noise it'll help with as well    Bat41 /1n4148 asymmetrical clipping as well
   Seriously thanks so much for the help and I'll post pics when I get home and le you know if everything goes well.   I already did all of those mods except I have to change the 20nf cap to 100nf and also switch the 47 nf cap back because I switched the wrong one thinking that was the input cap

I haven't messed with the TS circuit for a long time, but in my experience, changing the 51pF from ceramic to mica may or may not be audible. If so, it will only be with the gain and tone both cranked pretty high. Going to a higher value would have more impact. I've A/B'd ceramic vs film caps and heard an audible difference, but again, only with the gain and tone at extreme settings. Still, the mica will look rad in there!

Obie bong kanobie

#8
I changed the input cap to a mpsa 18 and from what I could see the pin outs arnt suppose to match but I'm not 100% positive this is correct if I'm having a issue. If anyone can help me verify. The other trannie is a 2Sc1815



Obie bong kanobie

#9
Ok so I made the input cap 100nf and that resistor like I said 2.2k   Something is wrong though because I'm only getting a signal if I strum really hard. Any ideas  should I take some voltages for you guys?   I'll modify this comment when I'm finished writing down the voltages and add them to here



Ic pin 8 9.70v, 7 4.88v 6 4.87v, 5 4.87, 4 0.00v, 3 4.80, 2 5.80, 1 4.90v