Vintage TS9 problem with low drive after installing IC socket

[strato2009]

So I installed an IC socket on a TS9 tubescreamer and now there's about 1/3 of gain of the amount it used to have before the IC socket. I installed it to try different chips.

Now what is there to do to troubleshoot this issue? Can I measure voltages somehow from the pins to see if they're correct or something else?

I checked the connections with multimeter, they are all in correct and don't overlap(solder's weren't sloppy)

I used the original and two different chips, all had low gain.

Secondly, I checked connections from IC to the bottom of the circuit board(solders), all were ok

Cables I checked by moving them with pliers

here's the socket used:
http://cimarrontechnology.com/images/products/detail/1104330841001000.jpg

Did I install correctly if the "U" shaped guide cavity is looking to the left if referencing to this picture? Also the chip's guide is facing left.

Essentially the drive knob just doesn't add drive, only a bit of volume.

THANKS

[GibsonGM]

I would guess that you have a bad solder doing.  One or more may not be making good contact with the PCB traces??    I would take and post voltages, yes! 

Also, could something have "come undone" when you took the PCB out of the enclosure??     That can happen, too!

[strato2009]

I would guess that you have a bad solder doing.  One or more may not be making good contact with the PCB traces??    I would take and post voltages, yes! 

Also, could something have "come undone" when you took the PCB out of the enclosure??     That can happen, too!

I checked the connections with a multimeter and they were fine.
checked the voltages on the IC, pin 5 showed 0 volts, pin 8 9 volts and the rest were in the middle, I suppose this is correct? I measured by plugging a cord into the input and with a multimeter between the battery pole and the pins, is this correct?
Any suggestions on troubleshooting this?

[ShredderNemo]

I had a similar issue occur when I socketed a chip in my TS-9 as well. Turns out, the gain pot had managed to turn a bit and was grounding out against the enclosure. Maybe check for grounding issues along the gain's signal path.

[GibsonGM]

I had a similar issue occur when I socketed a chip in my TS-9 as well. Turns out, the gain pot had managed to turn a bit and was grounding out against the enclosure. Maybe check for grounding issues along the gain's signal path.

If the socket tests fine...and your description is about right....then I'd suspect that something else got moved, bent/cracked/disconnected like Nemo is saying....this is part of the fun of DIY and modding - finding what we messed up!    Keep at it, you'll get it.   

Have you tried "hanging it out of the box" and turning it on, while upside down? CAREFULLY so as to not have PC parts touch the metal enclosure (which would probably kill it)?     Sometimes this helps me to see if something IS touching that shouldn't, like he said.

[strato2009]

I had a similar issue occur when I socketed a chip in my TS-9 as well. Turns out, the gain pot had managed to turn a bit and was grounding out against the enclosure. Maybe check for grounding issues along the gain's signal path.

If the socket tests fine...and your description is about right....then I'd suspect that something else got moved, bent/cracked/disconnected like Nemo is saying....this is part of the fun of DIY and modding - finding what we messed up!    Keep at it, you'll get it.   

Have you tried "hanging it out of the box" and turning it on, while upside down? CAREFULLY so as to not have PC parts touch the metal enclosure (which would probably kill it)?     Sometimes this helps me to see if something IS touching that shouldn't, like he said.

I will try hanging it out.

I think the problem is somewhere in this part

How can I locate these components as I'm not very good at reading schematics?

Can you point them out to me in the attached image please(It's identical to my tubescreamer)?


thanks

[ShredderNemo]

http://imgur.com/GkgGs9D

This is most of the gain stage and the two wires going to/from the pot

[GibsonGM]

I just looked at your post more closely, strato.   Pin 4 should be ground, ZERO volts...you sure it was pin 5 that had zero??  If so, a short in that area, most likely.   

If you check and 4 IS zero, pin 8 9v, and the rest in the middle, proceed....

Check all wires to the drive pot.  I don't think the parts in the loop are bad (why would they be?)...I suspect a bad jack connection to chassis (bad ground), or the pot itself.  But hard to say from a distance.    You COULD have messed up a trace in the area around that feedback loop, which is why I was suggesting really testing continuity there...it is the 2 diodes under the IC in that pic...on the line "4 J 1" and then the 51p cap, 2 diodes.

Might need to audio probe if the above doesn't tell you anything.

[strato2009]

I just looked at your post more closely, strato.   Pin 4 should be ground, ZERO volts...you sure it was pin 5 that had zero??  If so, a short in that area, most likely.   

If you check and 4 IS zero, pin 8 9v, and the rest in the middle, proceed....

Check all wires to the drive pot.  I don't think the parts in the loop are bad (why would they be?)...I suspect a bad jack connection to chassis (bad ground), or the pot itself.  But hard to say from a distance.    You COULD have messed up a trace in the area around that feedback loop, which is why I was suggesting really testing continuity there...it is the 2 diodes under the IC in that pic...on the line "4 J 1" and then the 51p cap, 2 diodes.

Might need to audio probe if the above doesn't tell you anything.

Yes it was actually the 4.
I checked the drive pot's wires with multimeter's audio probe, they were fine. But I noticed the level pot is touching the chassis, is this OK? Also checked the input plug's ground, was ok.

the drive pot measured 600k

"You COULD have messed up a trace in the area around that feedback loop, which is why I was suggesting really testing continuity there...it is the 2 diodes under the IC in that pic...on the line "4 J 1" and then the 51p cap, 2 diodes."

I checked this with the multimeter's diode measurement function it showed 652 on the display, I suppose they were ok? That's all I could think about checking on this, anything else I can check?

[Ben Lyman]

If one or both of those diodes becomes detached it might behave like the "Comp Cut" switch on the Fulltone Fulldrive II. Not only will the pedal function like a clean boost, losing (almost) all distortion, but it will also become quite noticeably louder.
Does it seem like you have extra volume output? More than you remember it having?

[antonis]

I don't like the tantalum cap next to IC...

[strato2009]

I don't like the tantalum cap next to IC...

It could be that the heat fried it? Or other nearby components since I used a solder wick to remove the original IC?

Also there's the green cap under the IC, do you guys know what values these should be so I can replace them? Also, if they would be bust, would that affect the amount of drive?

Ben, I didn't notice more output, but could try replacing those diodes, what codes do they have?

[antonis]

It could be that the heat fried it?

Most possible..

As far as I can recall, this is a 220nF/35V which acts as a lowpass filter with 1k resistor just right after IC's out (cutoff at about 720Hz) and it's actually there for "harsh" highs cut..

If there is a severe "reverse degradation" of it's nominal value (i.e. higher capacity X10) it results in lowering the cutoff frequency to 72Hz (which is lower than low open E)..

Maybe, IF it's defective, it mainly acts as a simple resistor forming a voltage divider with the 1k one, so you have a "fixed" loss for all frequencies...

[strato2009]

It could be that the heat fried it?

Most possible..

As far as I can recall, this is a 220nF/35V which acts as a lowpass filter with 1k resistor just right after IC's out (cutoff at about 720Hz) and it's actually there for "harsh" highs cut..

If there is a severe "reverse degradation" of it's nominal value (i.e. higher capacity X10) it results in lowering the cutoff frequency to 72Hz (which is lower than low open E)..

Maybe, IF it's defective, it mainly acts as a simple resistor forming a voltage divider with the 1k one, so you have a "fixed" loss for all frequencies...

Do you suggest also replacing the green small cap under the IC in the picture? What would be it's value and can it affect the amount of drive, after all it's in the drive circuit?

I will replace the orange one to the right in the picture from the IC.

[antonis]

Do you suggest also replacing the green small cap under the IC in the picture? What would be it's value and can it affect the amount of drive, after all it's in the drive circuit?

I think that it's the 51pF cap in lowpass filter with the Gain pot + 51k resistor...

I shouldn't suggest replacement for anything "just in case of" but you can desolder one leg (and raise it up) to check if it's closed (short-circuit) - but in this case you shouldn't get any gain at all...
(IC should act as a simple buffer..)

[strato2009]

Do you suggest also replacing the green small cap under the IC in the picture? What would be it's value and can it affect the amount of drive, after all it's in the drive circuit?

I think that it's the 51pF cap in lowpass filter with the Gain pot + 51k resistor...

I shouldn't suggest replacement for anything "just in case of" but you can desolder one leg (and raise it up) to check if it's closed (short-circuit) - but in this case you shouldn't get any gain at all...
(IC should act as a simple buffer..)

Actually there's so little gain that it could come through the increase in level.

So would you suggest replacing these two caps next to the IC?

The 51pf value is hard to find, I think 50pf should be fine and does the voltage matter?

[antonis]

Actually I don't get any gain, only through the increase in level I get the gain.

Probably, you mean that you get Volume...
("Gain" have to be translated as "Distortion" in your circuit, even at lower Drive pot setting (20dB)

Replacing the ceramic (pale green disk) cap should be a good idea - mainly for checking and clearing the neighbour junctions, like those around the clipping diodes..
(try first to remove the cap and check for getting diffent gain with various Drive pot settings - then replace it..)

[strato2009]

Actually I don't get any gain, only through the increase in level I get the gain.

Probably, you mean that you get Volume...
("Gain" have to be translated as "Distortion" in your circuit, even at lower Drive pot setting (20dB)

Replacing the ceramic (pale green disk) cap should be a good idea - mainly for checking and clearing the neighbour junctions, like those around the clipping diodes..
(try first to remove the cap and check for getting diffent gain with various Drive pot settings - then replace it..)

If I can't find 51pf, how close the value should be at most for it to function properly?

I feel like the problem indeed should be in the drive circuit.

[strato2009]

OK so I disconnected the 51pf cap and there were no change in amount of drive, does this mean if I'll replace it things should go back to normal?

Would 56pf or 47pf cap make any difference?

[GibsonGM]

I think you're easter-egging, my friend     If you have a vintage effect, why change parts that don't need to be changed?  Is it still vintage then?  You're going to change the cap, and maybe more but - you KNOW the cap, etc. is bad??   

That cap is just working as a filter in the feedback loop, it has little to do with actual volume!  It may help reduce some harshness in the sound, is all.  It is so tiny that you may not even hear the frequencies it affects.  If it is not burned to a short (test with meter!), then it is fine.

***  If the back of your pot has continuity with any of the 3 terminals of the pot, then it grounding out IS a problem.

You could check for continuity across the feedback loop, making sure the drive pot is set in the middle or so, so it won't represent a short to your meter.   You could make sure that 4.7k resistor IS connected to ground at one end...and that the cap above it isn't shorted, altho unlikely.  Most problems come from US soldering etc, so that has to be looked at over and over.

Once settled that the feedback loop is ok....could your problem be further along?  I would AUDIO PROBE that area, at this point. Each pin, carefully.  FIRST thing that is suspicious are the controls....the output of that opamp goes to the tone control - if THAT pot were bad, could it create a big load on the circuit?   Keep it simple, you don't have to rebuild the effect starting at that part of the circuit!!