Help - Tube Screamer Problem - op amp inserted incorrectly

[nation]

Hi All

I have a problem which I hope the forum can help me with.

I just finished a buffered Tube Screamer from the Tagboard blog:

https://tagboardeffects.blogspot.com/2012/02/ibanez-ts808.html

The pedal worked perfectly when I first fired it up, only problem was a low output volume, I had to turn up volume to 4 oclock to get unity. As I was experimenting with a possible fix I reversed the op amp while the pedal was powered on. When I put the op amp back into it's correct orientation the pedal no longer works. When turned on I get a very faint (almost non existent) distortion sound when all the knobs are turned up. When bypassed, a get a full signal, this even when there is no power jack in the pedal.

I have tested the pedal with other known working opamps and the result is the same. I assumed I might have burned an electrolytic capacitor so I replaced all 3 and the problem is still there.

What could the problem be here? I have used tantalum caps for the two 220nf caps, oriented +ve side to tone 1 and tone 2. Could the problem with tantaulums? I imagine I must have burned something when I reversed the opamp but have no idea what. I tried audio probing the circuit but really I have no idea what I am looking for. What damage could be caused by reversing the op amp?

[duck_arse]

well you can melt the internals of the opamp, for one thing, but this usually produces so much internal heat that it will blow the top out of the IC. you will need to post your IC pin voltages before we can diagnose anything. do you have any other dual opamp you can swap in? they are cheap enough these days to just turf and forget.

and your volume problem means something else is wrong, so we want the transistor voltages as well, AND photos of what you have built.

merry xmas?

[Kipper4]

I did similar last week with a tl072 fried the little bugger, nearly melted the breadboard.
Good job they're cheap.

[thetragichero]

lm308 with supply voltages switched let out the magic smoke. from what i hear the way to get good tone is to keep the smoke inside the package. unfortunately i was unable put the smoke back in 😥

[nation]

Thanks all.

Here are my voltages with a 9.46v power supply:

Q1   C   9.46
   B   5.28
   E   4.94
Q2   C   9.48
   B   5.27
   E   4.94
IC   1   6.23
   2   6.25
   3   6.23
   4   0
   5   9.3
   6   9.27
   7   9.27
   8   9.46

I have also attached some build pictures below. I damaged the vero strip when replacing the 100uf capacitor hence the bridge wire on the 3rd row from the bottom. I have double checked and it's not touching the 2nd row.

I have built a buffered version and strangely am getting a clean output when the pedal is bypassed even without a power supply attached. As mentioned, apart from having to crank the volume to reach unity, the the pedal worked great previously. The problem only arose when I reversed the opamp. A few points -

- I have checked this op amp in another TS pedal I built previously and this opamp works.
- I have tried other op amps in this pedal and it still doesn't work. The result is the same, just a very faint distortion sound.
- The opamp didn't get hot when I corrected it's orientation when the error occurred. I sizzled an OPA2134 on another pedal last week and that got hot very hot very quickly.

[duck_arse]

assuming you have counted correct all your track cuts and assuming you have all your links and the dreaded double-links counted and accounted for, an all correctly placed .......

there is a 220nF cap, bottm right near a 100nF cap, it is one row low on the botttom end. and by law we must ask - are those tantau caps or plcc, and if tantalum, are they fitted with the marked (+) facing the right direction? we really like to see the circuit diagram thet matches the layout, so we know you have the right orientation .....

fix that cap, then pull the IC out of the socket, power up and measure the voltages on the empty socket pins. post them here, and also measure the Vref/bias voltage - I'd point you to "A" spot on the circuit, but, well, can't.

and one last thing - why did you cut the lower left side 4k7 out? again, circuit diagram.

[edit :] forgot to ask - what type number transistors are you using?

[idy]

The bias 4.5v is the seventh row up from the bottom...opposite the input (there's a cut to seperate the two. A 10k to 9v, another to ground, 2 510k to the transistor bases, another pair of  10 ks to the opam pin 3 and 5. All these places need to be +-4/5v. They aren't.

[Slowpoke101]

You have a slight error with the rightmost 220nF capacitor. Have a look at the following image.



The image also shows the correct polarity (yellow + signs ) for the 220nF capacitors. From what you have posted before, you stated that you used tantalum capacitors and you did orientate them correctly but the rightmost capacitor has had its negative lead wired to +9VDC and not GND (0V ) - oops....Best to replace that particular capacitor as tantalums really do not like being reversed polarised and can cause some weird problems later.

[nation]

Thanks all for the help on this.

I have ditched the tantulum caps and installed regular film caps and corrected the row error for the second 220nf. The pedal now works and the unity volume seems to be on par with a modified TS I built previously. Only problem I now have is the treble content on my tone pot is concentrated in the last 20% of the pot rotation. This was throwing off my estimation of unity volume levels in my original post. I used a W20k pot and will experiment tomorrow with different tone pots.

assuming you have counted correct all your track cuts and assuming you have all your links and the dreaded double-links counted and accounted for, an all correctly placed .......

there is a 220nF cap, bottm right near a 100nF cap, it is one row low on the botttom end. and by law we must ask - are those tantau caps or plcc, and if tantalum, are they fitted with the marked (+) facing the right direction? we really like to see the circuit diagram thet matches the layout, so we know you have the right orientation .....

fix that cap, then pull the IC out of the socket, power up and measure the voltages on the empty socket pins. post them here, and also measure the Vref/bias voltage - I'd point you to "A" spot on the circuit, but, well, can't.

and one last thing - why did you cut the lower left side 4k7 out? again, circuit diagram.

[edit :] forgot to ask - what type number transistors are you using?

I built this off the vero layout on tagboard effects so wasn't following a schematic. I did look at a schematics found online when trouble shooting and noted the +ve side of the two 220nf tantalum caps going to the tone 1 and tone 2. I'm not sure if I read my tantalums +ve and -ve correctly when installing. See pictures below.

I have gone over the board again, checked the resistor and cap values and the links and cuts and all seems to be in order including the double link under the IC.

The 4k7 - is this the LED resistor? Some of the LED colors I'm using are quite dim with 4k7 so I wired it offboard but ended up with the 4k7 as on the footswitch.

IC is a JRC 4558 and the transistors are 2N5088.

For reference here my new voltages with the IC in:

Q1   C   9.46
   B   4.01
   E   3.61
Q2   C   9.46
   B   4.01
   E   3.61
IC   1   4.72
   2   4.74
   3   4.71
   4   0
   5   4.72
   6   4.72
   7   4.72
   8   9.46

My voltages are the same at the sockets when the IC is removed.

You have a slight error with the rightmost 220nF capacitor. Have a look at the following image.



The image also shows the correct polarity (yellow + signs ) for the 220nF capacitors. From what you have posted before, you stated that you used tantalum capacitors and you did orientate them correctly but the rightmost capacitor has had its negative lead wired to +9VDC and not GND (0V ) - oops....Best to replace that particular capacitor as tantalums really do not like being reversed polarised and can cause some weird problems later.

Thanks for the picture, good for a paint by numbers guy like me. I have attached pictures of my tantulum orientation after fixing the row error and before I replaced them with the film caps. Am i reading +ve and -ve correctly on the tantalums?

[Kipper4]

Voltages look good now. Have you tried and tested it since yet?

[duck_arse]

like the boss ^ sez, looks good voltages wise.

I have attached pictures of my tantulum orientation after fixing the row error and before I replaced them with the film caps. Am i reading +ve and -ve correctly on the tantalums?

yes and no - so, no. you have the wide spread one correct as per Slowpoke101's dia, but the narrow spaced one is/was reversed.

seeing as you have those giant 1uF caps onboard, it really makes no sense to mess with tantalum 220nF. box caps would do just as well, without any polarity issues [or future drying-out issues as you'd get with Al electros], except for that long leg stretching. carry on, excellent work, get to that pot taper problem.