OKKO Diablo + / no distortion?

[mug]

Hi all,

I'm looking for help with the OKKO diablo, I'm facing some problems with that... I already posted on tagboardeffects, but here I can add some photographs which could make it easier.

I used the layout here:
http://tagboardeffects.blogspot.de/2012/09/okko-diablo-modded-monster-pot-edition.html

I skipped the booster and used a standard wiring scheme as described here:
http://1.bp.blogspot.com/-k5Sh68yVU18/TzGRFKbiALI/AAAAAAAAAlk/CbfaaduUjYQ/s1600/%21Offboard+wiring.png

Now the trouble:
In bypass everything is fine, and when the effect is switched on I can hear the guitar and the controls are working (level changes volume, bass, tone, body and presence change the sound, feed also affects loudness...) but there is NO distortion, only a slight background noise. I tried both battery (fresh) and (good!) 9V adapter but nothing. Nothing. Result: frustration

Here the voltages I measured:

IC (same for 9 and 18V mode):
1 9.31 8 9.31
2 4.53 7 4.92
3 0 6 7.24 (!)
4 0.15 5 0.33

Transitors (18V/9V mode):
Q1 / Q2 / Q3 / Q4 / Q5
D 8.6/4.3 17.5/9.0 8.1/3.9 17.5/9.0 17.5/9.0
S 0.5/0.4 9.1/4.8 0.1/0.1 9.1/4.8 6.2/3.5
G 0/0 8.4/4.3 0/0 8.4/4.3 6.5/3.5

Pretty close to what Kostis wrote here:
http://tagboardeffects.blogspot.de/2012/09/okko-diablo-modded-monster-pot-edition.html

but there are some (I think) significant differences:
IC 6 is a bit high (higher than 7)
and in Q2 and 5 G is almost equivalent to S...

I attached some pictures.
Any idea what could cause the problem? Help is highly welcome!

Board:


With switch and pots:


Solder side:

[Hozy31]

Had a look at your pictures and it looks like some of your soldering could do with a bit more solder. I can definitely see some incomplete soldering. I would try going over your soldering first and make sure they completely cover the holes by adding more solder. One of the things i do is to hold the board in front of a light. You don't want to see any light shining through the soldered areas. Obviously this only really works for resistors, diodes and jumpers but it helps.

Hope you get it rockin'  \m/.

Edit: The black wire on the left (2nd down) also looks like it may be touching more than one track but its hard to really tell.

[mug]

I'm gonna check that - thanks! Since I get a signal in both bypass and switched on and the pots have an effect I dont think the wires are wrong...

[mug]

OK, I checked the soldering (re-flowed most of them) and made sure that there are no shorts (scraping with a knife...). I also checked continuity between the components and the respective strip lines - seems ok, but still there is a signal but no distortion...
Could the voltages point towards a bad chip?

[Frank_NH]

What transistors (jfets) did you use?  If you used something other than j201 or 2n5457, check the pinouts.  You should be getting some distortion for sure, as this is a dual mu amp jfet circuit.   Also, the gate and source voltages should probably not be as close as yours are.  Check the two caps there (47 nF and 1 uF) to make sure they are OK.



 

[mug]

Thanks for your comment - I use J201, so the pinouts are ok. Maybe I'll get some 2n5457 to test them as well. Changing the 47nF for a new one did not help, I have to get a new 1uF today to check that, too.

[mug]

In another vero for the OKKO Diablo by Harald from Sabrotone I found that Source and Gate of Q4 are labelled to be connected via a 1 µF NP cap (non-polarised = bipolar):

http://www.sabrotone.com/?attachment_id=620

Could that mean something?

[Frank_NH]

No, you can use a polar 1 uF cap if you want as shown in the tagboard vero layout.

If you still aren't getting any distortion, it's time to use an audio probe.  I'm thinking that your J201s may be suspect, but there's no way to know unless you can test them.  Try 2n5457s and see what you get.

Good luck!

[mug]

I'll be busy the next days but will try with audio probe and see if I can get some 2n5457s - thank you so far, I'll report what happened!

[rocket88]

if they are defective J201's you need to make sure you get them from a reliable source, so try not to order them or 2N5457's from random sellers on ebay, especially china ones IMHO. there are to many of us that have been burnt by bad fets from china that to me it's not even worth the risk.

in any event i hope that it ends up being nothing more then a bad fet.

[mug]

 OK, finally got it working!
After waiting for ages since my order got stuck at the customs I recieved a batch of 2N5457's and it came alive instantly. Out of curiosity I tried new J201's as well and found out one of the originals was bad.
This thing rocks - so it was worth the headache

Thank you for your helpful advice!!!

[Frank_NH]

Cool!  Another distortion box saved!