please help me debugging a shaka tube

[beatnik]

I've built the shaka tube by aron nelson with paul marossy layout at this link:
http://www.diyguitarist.com/PDF_Files/ST1590BB-PCB_9-9-06.pdf

I tried and tried but the pedal doesn't work. The tube is hot and lightning but no sound comes from the amplifier.
I use a 12vac 500mA power supply.
I tried to measure the voltages and i found that anyway i set the trimmer V- pad has always 0 V, unless bias and V+ change.
Where is my mistake?

Please help me

Giacomo

[ik6gpy]

Controlla per ordine se:
1) Ci sono saldature che non toccano le piste
2) Se il verso dei 2 1N4001 è giusto
3) se la resistenze da 10ohm e quella da 1k (sempre sulla basetta dell'alimentazione) sono bruciate.

Se vuoi un consiglio, quando riesci a farlo funzionare, avvolgi la basetta dell'alimentazione prima con del nastro isolante e poi con della carta argentata, in modo da isolarla. Altrimenti farà sempre un fastidiosissimo rumore di fondo

[beatnik]

I've used 1N4007 instead of 1N4001 maybe its the problem?
I used the audio probe: everything is ok around the IC (drive pot works well) but no sound comes out from the 6-7-8 pins of the tube (tone and vol pots doesnt work).
I also put new 10 ohm and 1k resistors in the power pcb but nothing has changed.
Or maybe is i wiring problem of the grounds.
I connected the dc jack positive to 12vac hole on power pcb and negative to GND hole on power pcb. negative is also connected to input jack shield.
The other two holes of the power pcb are connected to the tube.
Then Input gnd goes to input jack shield and Out gnd goes to output jack shield.
Is it right?

[ik6gpy]

Gli 1n4007 vanno benissimo. Il tuo è probabilmente un problema del trimmer. Devi inserirlo sulla pcb con la piedinatura esatta. Il piedino che si trova indietro rispetto ai 2 esterni è il centrale, basati su quello. Il centrale come vedi dallo schema deve essere inserito sulla pista del Bias.
E' molto probabile che tu abbia messo il trimmer con la piedinatura sbagliata

[beatnik]

il trimmer era nella posizione corretta, anche perchè le distanze tra i tre piedini combaciavano perfettamente con i fori della pcb.
io ho provato anche a cambiare i diodi e a risaldare il trimmer, ma non cambia nulla.

[dschwartz]

mammma miaaa!!!

[bancika]

I'm not an admin or something, but wouldn't it be better if we all used english on public forum?
otherwise, your comment will be useful to 2% of visitors (if that)...

[beatnik]

trimmer is in correct position, but i still cant make any change on V-
i also changed the diodes and the resistors. they weren't the problem

any suggestion?

[beatnik]

Please i need some help i'm not so skilled to resolve this problem by myself 

I disconnected the power pcb from the tube and from the other pcb, then measured the voltages and wrote them on the scheme.



Electrolitic caps are 25v... maybe they are burned by higher voltage?
I dont know what else can be...

Please help me it's only my second pedal 

[bancika]

how could you get 42VDV from 13.9VAC? Make sure that you measure AC before rectifier and DC after.

[Paul Marossy]

If you really are getting 42V, your electrolytic caps may well be damaged, and your opamp would be for sure.

You must have some things miswired. You need to double check ALL of the offboard wiring, including the tube socket.

[beatnik]

After I rebuilt some bad solders the shaka tube finally came to life!!! 
I'm very satisfied of my work and i would thank aron and paul marossy for schematic and layout, and everybody who replied in this topic: your help was the key to complete the pedal.

I like the sound of this pedal pretty much but i would improve it: i think has too treble, and even buzz on bass notes, wich i dont like at all.

These are the voltages on 12ax7 pins, maybe there is something wrong?
1: -3,20
2: -10,78
3: -10,82
4: 13,0 ac
5: 0.00
6: -3,29
7: -10,82
8: -10,91
9: 6,3 ac

[ik6gpy]

The buzz on the bass notes is a bias problem. Try different positions of the bias trimpot till you hear the best sound.
It's true, it gets very trebly. Try to replace the 2.2uF cap on the opamp reaction with a 4.7uF cap. Then try a capacitor to ground right before the volume pot (start with 0.022uF). Mine sounds very good with a 0.047uF cap. You can even add a bright switch wich bypasses this cap to have the original sound. At last experiment with different tubes. 

[beatnik]

i don't know how to correct this bias problem because anyway i set the trimmer i have this problem. with the trimmer all turned down is less but you can hear it anyway. maybe because my power supply gives 13v instead of the required 12v?
I will replace the 2.2uf capacitor, but i dont understand where to put the other capacitor.
Please let me know.