Skaka tube wrecked IC?

[stenns]

I just finished my shaka tube build today, and it didnt work right away.  As I checked voltages on each of the tube pins, I could manage a poping sound or something, but when I measured the IC (TL072 dual opamp), the voltages registered, but no clicking sound.  SO, i double checked my IC orientation, and it was in BACKWARDS!! So i moved it around and it sounds like crap.  Veryyy high, solid-state-sounding, buzzy gain.  I adjust the bias to -11.3 volts-ish and can make it sound decent but not tubular at all.  Also something wierd, the gain control doesnt affect the gain, or anything.  It is completely useless.  Vol. works, tone works. SO i think i wrecked my IC when it was in backwards and I am considering ordering a new one but dont want to if i dont have to.  Can anyone tell me some advice/how to check if it is good??

[stenns]

1.What does it do, not do, and sound like?

Plays my guitar, sounds like crap.  SS distortion (buzzy) with poor sustain

2.Name of the circuit

Shaka Tube w TL072 dual opamp

3.Source of the circuit (URL of schematic or project) =

http://diyguitarist.com/DIYStompboxes/ST1590BB.htm
http://www.diystompboxes.com/pedals/schems/shakatube.gif

4.Any modifications to the circuit? Y or N

NONE layout and circuit followed EXACTLY

Battery voltage? => 12v ac in. 

When connected (actual) 13.0v ish

Bias = 11.3v V+=13.1v V-=10.0v  (approximations)


IC voltages were normal as i remember them, i.e. equal to the V+ V- on the Vcc and Vee pins.  If you need the rest of the pins voltages let me know and I can do that.  Thankyou!

[george]

1.What does it do, not do, and sound like?

Plays my guitar, sounds like crap.  SS distortion (buzzy) with poor sustain

2.Name of the circuit

Shaka Tube w TL072 dual opamp

3.Source of the circuit (URL of schematic or project) =

http://diyguitarist.com/DIYStompboxes/ST1590BB.htm
http://www.diystompboxes.com/pedals/schems/shakatube.gif

4.Any modifications to the circuit? Y or N

NONE layout and circuit followed EXACTLY

Battery voltage? => 12v ac in. 

When connected (actual) 13.0v ish

Bias = 11.3v V+=13.1v V-=10.0v  (approximations)


IC voltages were normal as i remember them, i.e. equal to the V+ V- on the Vcc and Vee pins.  If you need the rest of the pins voltages let me know and I can do that.  Thankyou!

have you tried another dual op-amp (doesn't have to be TL072 as long as the pinouts match)?

[stenns]

The only thing i could get my hands on would be a TL082 from radio shack.  The pinout is the same, but it says JFET operational amplifier.  any dif?
http://www.radioshack.com/product/index.jsp?productId=2062594&cp=&origkw=op+amp&kw=op+amp&parentPage=search

I will bring back as many 8pin ICs as i can from my school and try them all.  do you think the TL082 would be a good permanent substitute if i can't find anything better?

[trevize]

a lot of dual opamp would work: 4558, tl072, tl082, ne5532, lf353 (probably)

[Paul Marossy]

That sounds like it's misbiased or something. Try a different opamp and see what happens.

[stenns]

im waiting on getting another dual op amp...all the radio shacks in my area transformed into "The Source by Cicruit City"'s, which do NOT carry TL082's, only single op amps.  In the meantime i took my guitar input jack and grounded it with a screwdriver, then touched the tip to the leads from certain tube pins.  I got some guitar sound with the grid of stage 2 in the 12ax7 (pin 7, very low volume and no distortion) but nothing from the grid of stage 1 (pin 2).  I played with the bias control and didnt get too much of a change.  Figured it might mean something, but im still thinking that my IC is toast.  I am gonna go and play around with another IC socket, and try to run the circuit using the other opamp out of my TL072 to see if it work.  Not right now though.  Thanks guys!

[AdamB]

This may be a stupid question, but have you wired up the heater on the tube?

-Adam

[stenns]

ahha yah i actually had this problem when i built an ax84 p1ex a few months ago.  I only wired 2 of the heater leads, forgetting one other.  On this schematic it appears that only 2 are used, correct?  cause i only have 2 wired, and i can spot 2 of them glowing when i look in.  One thing i considered was that I mixed up which one of the heater leads goes to ground (not positive if that even matters).  I had it figured out but its hard to double check cause the wires are all twisted up.

[Connoisseur of Distortion]

the 082 will work fine, but with a bit more noise. nothing serious.

[AdamB]

In this circuit I think you have pins 4 and 5 as heaters, which should be getting about 12V. It doesn't matter which is +ve and which is ground as the heater filament is just a bit of resistive wire. I think the recommended heater voltage is 12.6V but it will work with higher/lower voltages, so just 12V or 13V will be fine.

-Adam

[stenns]

Do you know why pin 9 isnt used on this circuit?

[Paul Marossy]

Do you know why pin 9 isnt used on this circuit?

Because it is operating on 12.6VAC. If it were running on 6.3VAC, you would use Pin 9 and connect pins 4 & 5 together.