Ibanez Ts8 / ts808 tubescreamer help tube screamer

[hendrix2489]

just a quick question i am having the same problem as Wolfgangblue5150 http://www.diystompboxes.com/smfforum/index.php?topic=42484.0

i have volume and tone knobs working but no drive just a clean sound,  i am using a 500k audio taper (log) pot and i know it works.  i will post readings later on because I'm at work.

any help would be great thanks

[hendrix2489]

also does it really matter if i used some ceramic caps instead of film or vice-versa

[hendrix2489]

Here is the checklist to fill out:
1.What does it do, not do, and sound like? It sounds great bypassed but when switched, it is clean with no drive but tone and level work
2.Name of the circuit = Ibanez tubescreamer ts808 replica
3.Source of the circuit (URL of schematic or project) =  http://www.generalguitargadgets.com/index.php?option=content&task=view&id=90&Itemid=118
4.Any modifications to the circuit? No
5.Any parts substitutions? If yes, list them. yes, 47 pf for 51pf, 2m2 for 1m5, .02pf for .022pf
6.Positive ground to negative ground conversion? No
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => i use a 9v power supply
-  9.8v on board

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
C =9.8
B =2.5
E =3.5

Q2
C=9.8
B=2.5
E=4.75

IC1 (or U1)
1 -       
2 -
3 -
4 -   all pins are around 9.0v
5 -
6 -
7 -
8 -

[hendrix2489]

i also am getting readings on both leads of diodes

[heyniceguy]

IC1 (or U1)
1 -        
2 -
3 -
4 -   all pins are around 9.0v
5 -
6 -
7 -
8 -



well that's not right..... it should be closer to ....

IC1 (or U1)

1 - ~4.5v
2 - ~4.5v
3 - ~4.5v
4 -  0v
5 - ~4.5v
6 - ~4.5v
7 - ~4.5v
8 - 9v

the 4.5v measurement can vary, but pins 2 and 3 must be close to each other (few mV's), as well as 5 and 6.

[hendrix2489]

i checked and they are not close together.  i have the ic plugged into an ic socket,  the ic is the right way though. 

B100k linear pot, w25k tone pot from small bear, a500k audio pot

3pdt true bypass switch wired as on generalguitargadgets.com

diodes have voltage on both leads

[heyniceguy]

i would try looking at places where pin1 and pin 2 could be shorted, possibly by a fat solder joint or something. looking at the layout, if you do have pins 1 and 2 shorted, then the opamp would act like a low gain buffer, thus giving you no gain control, but a clean signal.

im looking at the layout on GGG.com and some places to check are:

1) solder bridge between pin 1 and 2 on opamp
2) pads where drive 1 come close to pads of D1/D2/C4
3) space between pads where D2 and D3 go.
4) check diodes themselves for shorts
5) pads where D1 and D2 are close.
6) pretty much ANYTHING in the feedback loop (area underneath the "SCREAMER" text on the layout).

[johngreene]

If pin 4 of the IC is near 9V I'd say you are missing a ground connection somehow.

The bases of the transistors should be around 4.5V and about .6V higher than the emitters.

So, I recommend you check your grounds and the bias divider.

--john

[hendrix2489]

thanks johngreene and heyniceguy i will try these out when i get home and post results

[dosmun]

Also make sure your Drive pot hasn't twisted and  touching the side of the case.

[hendrix2489]

i have tried a lot of these things but still nothing , should i just solder the chip directly to the board instead of using the socket

[johngreene]

Are you still reading 9V on pin 4 of the IC?

[hendrix2489]

im gonna pull an all day-er tomorrow to try and get this working so i will solder the ic to the board and re do the readings

[hendrix2489]

just wondering how to check diodes for shorts so i can get off on the right foot tomorrow

[johngreene]

You would need to remove them to check them. You may want to try remove one, or both, and see if your gain jumps a lot. If so, then one of the diodes is shorted, if not, then you have something else wrong.

If the resistor/capacitor coming from the inverting input is open, you would have a simular problem.

--john

[hendrix2489]

i pulled the diodes and have seen a drastic change in tone, drive still doesnot work

[hendrix2489]

i pulled the diodes and have NOT seen a drastic change in tone, drive still doesnot work

[johngreene]

i pulled the diodes and have NOT seen a drastic change in tone, drive still doesnot work

So your are not getting any gain in the first stage. Either:

1. the Drive pot has a short across it somehow, somewhere.
2. The gain setting resistor/capacitor going from the inverting input is not seeing a path to ground.

--john

[hendrix2489]

 

i got it working, thank you all very much i do not know exactly how i fixed it but i took out the drive components and resoldered them, and also took out the ic socket and soldered the opamp directly into the board, i have exact readings of heyniceguy's post and it sounds amazing

thank you all once again and i hope ill be able to help out you guys as much as you helped out me

[heyniceguy]

its funny. i have this one broken wah pedal that has been a mystery for me for years. i just couldnt figure out what was wrong. and i  told myself back then "if you just resolder everything, it will probably fix it". but i refused to concede victory against that one bad component, which ever one it was. i wanted to KNOW what it was i was fixing and not just carpet bomb the project. so i put it away.

so last weekend i yanked it out when i had some free time. resoldered the whole board and whaddya know.

"wakka wakka bow bow wakka wakka"

sometimes thats all it takes. just put aside your curiosity and plug in the iron.