Need help for a shaka tube!!!

[j.frad]

Hi everyone!
I'm building a shaka tube out of the pcb layout found on paul marossy's website:
http://www.diyguitarist.com/
direct link to the file is:
http://www.diyguitarist.com/PDF_Files/ShTube1590BB-PCB.pdf (thanks a lot for creating this file)
he made the design out of this schematic by Aron nelson.
http://www.diystompboxes.com/pedals/schems/shakatube.gif

I finished making it but it doesn't work. the tube hottens and starts to glow red a little which I guess is normal! but the sound coming out is a big hum with a little bit of the guitar's signal (not overdriven)
My guess was it's the opamp that's making problems, I mounted it on a socket so I couldn't overheat it, but what seams strange is the pin connection of the opamp on the layout compared to the one on the schematic and to this file:
http://www.diystompboxes.com/pedals/ampins.GIF

Can anyone have a look and help me please?
Just one more question, juste to know if I didn't solder everything upside down: the layout shows all the components on top of the board but the lines (sorry can't name this part correctly I'm french), the lines that connect the parts together run underneath the board right? please tell me I didn't reverse it!

Anyway, thanks for you time!!
j.frad

[j.frad]

a little more info:
I had to replace the TL072 by a TL082, the 50K resistors by 47k and the two 1N4001 by 1N4007s
I used a 12V AC power supply and perfboard to mount everything.
I tried to make pics of the thing but they were too crappy noone could have seen a thing.
I checked the whole circuit for shortcircuits or polarity reversals and found no mistake...

[Paul Marossy]

I can asure you that my layout works. If you used a dual opamp, such as a TL082, it's not going to work. My PCB is designed around a single opamp, as in a TL071/81. It shows a TL071 on the PCB layout...  

[aron]

Try using a single op amp i.e. TL071 instead of a dual (like the TL072).

Aron

[j.frad]

ok! there's dual and single opamps! now i'll go to sleep less stupid!
thanks very much!
I guess that was the mistake! hope I didn't fry anything else...
thank you so much for your time and availability!!!
jules

[aron]

oooh I hope it fires right up when you put the single op amp in there.

[j.frad]

hey you know I never thought the error could be anyone's but mine right?...bye!

[Paul Marossy]

It should work once you get a single opamp in there, assuming all wiring is correct.  

[george]

I checked the whole circuit for shortcircuits or polarity reversals and found no mistake...

did you check for open circuits? Sounds like a dodgy earth connection to me

[j.frad]

Well I checked the wiring like 5 times, i think everything should be fine, i'll just check one more time...
I'll tell you how it went after opamp changing and all that....
(maybe I'll do a little page about that pedal when it works, cause I'm gonna have to build the box to put it into, in case anyone's interested about the little story...)
I'll be back!!

[Paul Marossy]

Couple of things to check:

Make sure all points labeled 12VAC, GND, V+, V- and bias are connected together. Also, on my wiring layout, the preamp tube is shown from the bottom - sometimes people wire the tube socket backwards...

[Paul Marossy]

Hey! Did you ever get it working?!

[j.frad]

hey!
well,i decided to start it all over, redid the whole thing on a new piece of perfboard  and it kind of works now!
however  i now have other problems: i get some kind of a gating effect that i don't know how to  fix...


i'll look around for an answer to that and i'll put sound samples on  the web this weekend so you can hear the trouble, in case youu can help me fix it!
i'm optimistic!!!
be back soon...
jules

[Paul Marossy]

I had that gating effect on the first one I built. I never did figure out the problem. I decided to rebuild it, and then it worked like a champ. That was build #2. Build #3 is the one in the Hammond 1590BB enclosure that I am using all the time now.  

Anyhow, I hope you get it working. I am not sure what the problem was before, but I know my PCB layout works, because I built my own working Shaka Tube from it. (Just for the record.  :wink:)

[j.frad]

well maybe i'll try with a different tube or opamp... or i'll rebuild the power section too...

it seems to be a bias problem as I read in the troubleshooting page on this site, and the gating effect does change if I change the bias, but it never disappears (i tried sweeping the bias from one extreme to the other and I still have some of it)

Since my wallwart is 12V AC (instead of 13 as you said you had on yours) I removed the 10ohm resistor in series with one of the ends in the power section but I don't think that could be the problem. what do you think?

anyway, I'll put samples soon if anyone can help I'd be really happy...

I'll be back!

[Paul Marossy]

Have you tried different tubes? Perhaps it might make a difference? Also, what is the mA rating of your wall wart?

[j.frad]

my wallwart is rated 1A 12VAC

[Paul Marossy]

What voltages do you measure inside your circuit? With a 1 amp power supply that is lightly loaded, everything will measure considerably higher since the whole circuit requires only about 180mA to operate. My guess is that your operating voltages are too high, especially for the opamp - which is probably causing that gating sound...

EDIT: Hmm... I just reviewed what transformer I used, and it's an 800mA, 13VAC. So, I guess, your voltages shouldn't be that much higher than mine would be. This is a little confusing to me, because a 12AX7 data sheet states that the heater current at 12.6V is 150mA, so why is so much current required for this circuit?! I guess the voltage drop must come into play at the voltage double circuit?

Anyone?

[j.frad]

between the two different builds you made did the one which didn't work and the other one have exactly the same tube and opamp?

Oh new stuff maybe related to this: i've just finished building a Tube Reamer out of runoffgroove.com but I did not use the 741 opamp but another one (it says 2748DC 313 and stuff I don't even know it's reference but anyway it wasn't the recommended one...) and I got the same gating problem...
I've just had enough of gating/battering sounds for the last few days and I was just about to go hang myself or get exorcised when I decided to try a TL 071 instead and now it works!

So I'm just wondering which opamps you have in your shaka, if they're the same TL 071s as you put on the layout or if you swapped it for something else...might be a false alarm...

[Paul Marossy]

Cool! In some instances, the exact opamp opamp used does seem to make a difference in a circuit. I don't remember exactly what opamp I used in my latest Shaka Tube build, but I believe that it's a JFET type single opamp, like the TL071.